| 1. |
- Wang, Zhongqiang, et al.
(författare)
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Realizing 18.03% efficiency and good junction characteristics in organic solar cells via hydrogen-bonding interaction between glucose and ZnO electron transport layers
- 2022
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 11:4, s. 1810-1816
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Tidskriftsartikel (refereegranskat)abstract
- Electron transport layers (ETLs) with excellent electron extraction capability are essential for realizing high efficiency in organic solar cells (OSCs). A sol-gel-processed ZnO ETL is widely used in OSCs due to its high mobility and suitable work function. However, the existence of defects usually results in low photovoltaic performance during the operation of OSCs. In this work, glucose (Gl) was used to passivate free OH traps via hydrogen-bonding interaction and formed ZnO/Gl ETLs with ZnO, which exhibited improved electron extraction capability and reduced trap defect density. Thus, a champion efficiency of 18.03% was obtained in a PM6:Y6 light absorber-based cell, which is >11% higher than that of the reference cell (16.15%) with a pristine ZnO ETL. Impressive enhancements by >11% were also observed in different fullerene and non-fullerene light absorber-based cells relative to that of the reference cell. This study demonstrates a new strategy to design ETLs for realizing high efficiency in OSCs.
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| 2. |
- Hu, Tianyu, et al.
(författare)
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Steric hindrance induced low exciton binding energy enables low-driving-force organic solar cells
- 2024
-
Ingår i: Aggregate. - 2692-4560 .- 2766-8541. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- Exciton binding energy (Eb) has been regarded as a critical parameter in charge separation during photovoltaic conversion. Minimizing the Eb of the photovoltaic materials can facilitate the exciton dissociation in low-driving force organic solar cells (OSCs) and thus improve the power conversion efficiency (PCE); nevertheless, diminishing the Eb with deliberate design principles remains a significant challenge. Herein, bulky side chain as steric hindrance structure was inserted into Y-series acceptors to minimize the Eb by modulating the intra- and intermolecular interaction. Theoretical and experimental results indicate that steric hindrance-induced optimal intra- and intermolecular interaction can enhance molecular polarizability, promote electronic orbital overlap between molecules, and facilitate delocalized charge transfer pathways, thereby resulting in a low Eb. The conspicuously reduced Eb obtained in Y-ChC5 with pinpoint steric hindrance modulation can minimize the detrimental effects on exciton dissociation in low-driving-force OSCs, achieving a remarkable PCE of 19.1% with over 95% internal quantum efficiency. Our study provides a new molecular design rationale to reduce the Eb.
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| 3. |
- Li, Wei, et al.
(författare)
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One-Step Synthesis of Precursor Oligomers for Organic Photovoltaics: A Comparative Study between Polymers and Small Molecules
- 2015
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 7:49, s. 27106-27114
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Tidskriftsartikel (refereegranskat)abstract
- Two series of oligomers TQ and rhodanine end-capped TQ-DR were synthesized using a facile one-step method. Their optical, electrical, and thermal properties and photovoltaic performances were systematically investigated and compared. The TQ series of oligomers were found to be amorphous, whereas the TQ-DR series are semicrystalline. For the TQ oligomers, the results obtained in solar cells show that as the chain length of the oligomers increases, an increase in power conversion efficiency (PCE) is obtained. However, when introducing 3-ethylrhodanine into the TQ oligomers as end groups, the PCE of the TQ-DR series of oligomers decreases as the chain length increases. Moreover, the TQ-DR series of oligomers give much higher performances compared to the original amorphous TQ series of oligomers owing to the improved extinction coefficient (epsilon) and crystallinity afforded by the rhodanine. In particular, the highly crystalline oligomer TQ5-DR, which has the shortest conjugation length shows a high hole mobility of 0.034 cm(2) V-1 s(-1) and a high PCE of 3.14%, which is the highest efficiency out of all of the six oligomers. The structure-property correlations for all of the oligomers and the TQ1 polymer demonstrate that structural control of enhanced intermolecular interactions and crystallinity is a key for small molecules/oligomers to achieve high mobilities, which is an essential requirement for use in OPVs.
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| 4. |
- Shi, Furong, et al.
(författare)
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A Nitroxide Radical Conjugated Polymer as an Additive to Reduce Nonradiative Energy Loss in Organic Solar Cells
- 2023
-
Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 35:23
-
Tidskriftsartikel (refereegranskat)abstract
- Nonfullerene-acceptor-based organic solar cells (NFA-OSCs) are now set off to the 20% power conversion efficiency milestone. To achieve this, minimizing all loss channels, including nonradiative photovoltage losses, seems a necessity. Nonradiative recombination, to a great extent, is known to be an inherent material property due to vibrationally induced decay of charge-transfer (CT) states or their back electron transfer to the triplet excitons. Herein, it is shown that the use of a new conjugated nitroxide radical polymer with 2,2,6,6-tetramethyl piperidine-1-oxyl side groups (GDTA) as an additive results in an improvement of the photovoltaic performance of NFA-OSCs based on different active layer materials. Upon the addition of GDTA, the open-circuit voltage (VOC), fill factor (FF), and short-circuit current density (JSC) improve simultaneously. This approach is applied to several material systems including state-of-the-art donor/acceptor pairs showing improvement from 15.8% to 17.6% (in the case of PM6:Y6) and from 17.5% to 18.3% (for PM6:BTP-eC9). Then, the possible reasons behind the observed improvements are discussed. The results point toward the suppression of the CT state to triplet excitons loss channel. This work presents a facile, promising, and generic approach to further improve the performance of NFA-OSCs.
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| 5. |
- Tang, Shi, et al.
(författare)
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Aggregation-Induced Emission by Molecular Design: A Route to High-Performance Light-Emitting Electrochemical Cells
- 2023
-
Ingår i: Angewandte Chemie - International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 62:23
-
Tidskriftsartikel (refereegranskat)abstract
- The emission efficiency of organic semiconductors (OSCs) often suffers from aggregation caused quenching (ACQ). An elegant solution is aggregation-induced emission (AIE), which constitutes the design of the OSC so that its morphology inhibits quenching π–π interactions and non-radiative motional deactivation. The light-emitting electrochemical cell (LEC) can be sustainably fabricated, but its function depends on motion of bulky ions in proximity of the OSC. It is therefore questionable whether the AIE morphology can be retained during LEC operation. Here, we synthesize two structurally similar OSCs, which are distinguished by that 1 features ACQ while 2 delivers AIE. Interestingly, we find that the AIE-LEC significantly outperforms the ACQ-LEC. We rationalize our finding by showing that the AIE morphology remains intact during LEC operation, and that it can feature appropriately sized free-volume voids for facile ion transport and suppressed non-radiative excitonic deactivation.
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| 6. |
- Wang, Chuanfei, et al.
(författare)
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Low Band Gap Polymer Solar Cells With Minimal Voltage Losses
- 2016
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 6:18
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Tidskriftsartikel (refereegranskat)abstract
- One of the factors limiting the performance of organic solar cells (OSCs) is their large energy losses (E loss) in the conversion from photons to electrons, typically believed to be around 0.6 eV and often higher than those of inorganic solar cells. In this work, a novel low band gap polymer PIDTT-TID with a optical gap of 1.49 eV is synthesized and used as the donor combined with PC71BM in solar cells. These solar cells attain a good power conversion efficiency of 6.7% with a high open-circuit voltage of 1.0 V, leading to the E loss as low as 0.49 eV. A systematic study indicates that the driving force in this donor and acceptor system is sufficient for charge generation with the low E loss. This work pushes the minimal E loss of OSCs down to 0.49 eV, approaching the values of some inorganic and hybrid solar cells. It indicates the potential for further enhancement of the performance of OSCs by improving their V oc since the E loss can be minimized.
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| 7. |
- Wang, Chuanfei, et al.
(författare)
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Ternary organic solar cells with enhanced open circuit voltage
- 2017
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Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855 .- 2211-3282. ; 37, s. 24-31
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Tidskriftsartikel (refereegranskat)abstract
- By introducing a non-fullerene small molecule acceptor as a third component to typical polymer donor: fullerene acceptor binary solar cells, we demonstrate that the short circuit current density (Jsc), open circuit voltage (Voc), power conversion efficiency (PCE) and thermal stability can be enhanced simultaneously. The different surface energy of each component causes most of the non-fullerene acceptor molecules to self-organize at the polymer/fullerene interface, while the appropriately selected oxidation/reduction potential of the non-fullerene acceptor enables the resulting ternary junction to work through a cascade mechanism. The cascade ternary junction enhances charge generation through complementary absorption between the non-fullerene and fullerene acceptors and aids the efficient charge extraction from fullerene domains. The bimolecular recombination in the ternary blend layer is reduced as the ternary cascade junction increases the separation of holes and electrons during charge transportation and the trap assistant recombination induced by integer charge transfer (ICT) state potentially reduced due to the smaller pinning energy of inserted non-fullerene acceptor, leading to an unprecedented increase in the open circuit voltage beyond the binary reference values.
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| 8. |
- Zhang, Bingke, et al.
(författare)
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Facile Synthesis of Organic–Inorganic Hybrid Heterojunctions of Glycolated Conjugated Polymer-TiO 2−X for Efficient Photocatalytic Hydrogen Evolution
- 2024
-
Ingår i: Small. - 1613-6810 .- 1613-6829. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- The utilization of the organic–inorganic hybrid photocatalysts for water splitting has gained significant attention due to their ability to combine the advantages of both materials and generate synergistic effects. However, they are still far from practical application due to the limited understanding of the interactions between these two components and the complexity of their preparation process. Herein, a facial approach by combining a glycolated conjugated polymer with a TiO2−X mesoporous sphere to prepare high-efficiency hybrid photocatalysts is presented. The functionalization of conjugated polymers with hydrophilic oligo (ethylene glycol) side chains can not only facilitate the dispersion of conjugated polymers in water but also promote the interaction with TiO2−X forming stable heterojunction nanoparticles. An apparent quantum yield of 53.3% at 365 nm and a hydrogen evolution rate of 35.7 mmol h−1 g−1 is achieved by the photocatalyst in the presence of Pt co-catalyst. Advanced photophysical studies based on femtosecond transient absorption spectroscopy and in situ, XPS analyses reveal the charge transfer mechanism at type II heterojunction interfaces. This work shows the promising prospect of glycolated polymers in the construction of hybrid heterojunctions for photocatalytic hydrogen production and offers a deep understanding of high photocatalytic performance by such heterojunction photocatalysts.
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| 9. |
- Cai, C. S., et al.
(författare)
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Polymer solar cells spray coated with non-halogenated solvents
- 2017
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248. ; 161, s. 52-61
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Tidskriftsartikel (refereegranskat)abstract
- Using spray-coating technique, we successfully fabricated conventional ITO-based and inverted ITO-free polymer solar cells (PSCs) based on a conjugated polymer poly[2,3-bis-(3-octyloxyphenyl) quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) as the donor and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) or [6,6] -phenyl-C71-butyric acid methyl ester (PC71BM) as the acceptor. Environment-friendly non-halogenated solvents were used to process the active layers. The influence of substrate temperatures and processing solvents on the photovoltaic performance of the ITO-based TQ1:PC61BM PSCs was systemically investigated. A higher substrate temperature can accelerate the solvent evaporating rate and afford a micro-textured rougher surface, which efficiently reduced light reflectance and enhanced absorption. Furthermore, finer phase separation was observed when using this high substrate temperature, which led to enhanced photocurrent due to the reduced bimolecular recombination. The device performance of spray-processed PSCs using the non-halogenated solvent mixtures was comparable to that of spray-processed PSCs using the halogenated o-dichlorobenzene (oDCB), which demonstrates that the non-halogenated solvents are very promising in spray-processed PSCs. This work sheds new light on developing efficient roll-to-roll compatible spray-coated PSCs with environment-friendly solvents.
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| 10. |
- Chen, W., et al.
(författare)
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Enhanced efficiency of polymer solar cells by improving molecular aggregation and broadening the absorption spectra
- 2019
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Ingår i: Dyes and Pigments. - : Elsevier BV. - 0143-7208 .- 1873-3743. ; 166, s. 42-48
-
Tidskriftsartikel (refereegranskat)abstract
- Alkylthio-substituted thiophene-based benzo[1,2-b:4,5-b’]dithiophene (BDT) was used to construct PBDTS-DTBT, a medium band gap donor-acceptor (D-A) polymer with 5,6-difluoro-4,7-bis[4-(2-octyldodecyl)thiophene-2-yl]benzo[c] [1,2,5]thiadiazole (DTBT). The incorporation of sulfur atoms into the side chains not only lowered the highest occupied molecular orbital (HOMO) energy level but also improved molecular aggregation and thus afforded lower band gap (1.68 eV) with full width at half maximum (FWHM) of 170 nm in comparison to that of the analogous polymer (PBDT-DTBT) without sulfur atoms in side chains. Therefore, the bulk heterojunction polymer solar cells based on PBDTS-DTBT with 2% diiodooctane (DIO) as processing additive showed a high power conversion efficiency (PCE) of 9.73% with high open-circuit voltage (V OC , 0.93 V), large short-circuit current density (J SC , 14.23 mA/cm 2 ) and high fill factor (FF, 0.735).
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| 11. |
- Chen, W., et al.
(författare)
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Revealing the Position Effect of an Alkylthio Side Chain in Phenyl-Substituted Benzodithiophene-Based Donor Polymers on the Photovoltaic Performance of Non-Fullerene Organic Solar Cells
- 2019
-
Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 11:36, s. 33173-33178
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Tidskriftsartikel (refereegranskat)abstract
- In this work, position effects of an alkylthio side chain were investigated by designing and synthesizing two copolymers based on a phenyl-substituted benzo[1,2-b:4,5-b′]dithiophene (BDTP) and difluorobenzotriazole (FTAZ). The polymer based on the meta-position-alkylthiolated BDTP, named m-PBDTPS-FTAZ, showed a relatively broader bandgap (2.00 vs 1.96 eV) and lower highest occupied molecular orbital (HOMO) energy level (-5.40 vs-5.32 eV) than its para-positioned structural isomeric analogue polymer (named p-PBDTPS-FTAZ), that is, m- A nd p-PBDTPS-FTAZ with the side chain structured as ethylhexyl-in the phenyl unit and hexyldecyl-in the FTAZ moiety. When blended with ITIC, m-PBDTPS-FTAZ showed a comparable crystallinity but more uniform morphology compared to that of p-PBDTPS-FTAZ. A high power conversion efficiency of 13.16% was achieved for m-PBDTPS-FTAZ:ITIC devices with a high open circuit voltage (VOC) of 0.95 V, which is higher than that of p-PBDTPS-FTAZ:ITIC devices (10.86%) with a VOC of 0.89 V. Therefore, m-BDTPS could be an effective donor unit to construct high-efficiency polymers due to its effectively decreased HOMO energy level of polymers while still maintaining good molecular stacking.
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| 12. |
- Dang, D. F., et al.
(författare)
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Manipulating backbone structure with various conjugated spacers to enhance photovoltaic performance of D-A-type two-dimensional copolymerse
- 2014
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Ingår i: Organic Electronics: physics, materials, applications. - : Elsevier BV. - 1566-1199. ; 15:11, s. 2876-2884
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Tidskriftsartikel (refereegranskat)abstract
- A class of low band-gap two-dimensional conjugated polymers of PBDTT-FQ PBDTT-TQ PBDTT-BTQ and PBDTT-TTQ was designed and synthesized, which contains the same di(alkylthiophene)-substituted benzo[1,2-b:4,5-b']dithiophene (BDTT) and 6,7-difluoro-quinoxaline (Q) units, as well as various conjugated spacers of furan, thiophene, bithiophene and thieno[3,2-b]thiophene in the main chain. Significant effect of the varied spacers between the BDTT and Q units on the thermal, optical, electrochemical and photovoltaic properties was investigated and observed for these two-dimensional copolymers in the polymer solar cells. The maximum power conversion efficiency of 5.9% with a short circuit current of 13.7 mA/cm(2) and a fill factor of 0.56 was obtained for the PBDTT-TQ with thiophene spacer in the bulk hetero-junction PSCs using [6,6]-phenyl-C-71-butyric acid methyl ester as acceptor.
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| 13. |
- Du, Siying, et al.
(författare)
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Nonfullerene acceptors from thieno[3,2-b]thiophene-fused naphthalene donor core with six-member-ring connection for efficient organic solar cells
- 2021
-
Ingår i: Dyes and Pigments. - : Elsevier BV. - 0143-7208 .- 1873-3743. ; 185
-
Tidskriftsartikel (refereegranskat)abstract
- Comprehensive design ideas on the fused-ring donor-core in state-of-the-art acceptor-donor-acceptor (A-D-A) nonfullerene acceptors (NFAs) are still of great importance for regulating the electron push-pull effect for the sake of optimal light-harvesting, frontier molecular orbital levels, and finally their photovoltaic properties. Herein, thieno[3,2-b]thiophenes were fused in bay-area of naphthalene via six-member-ring connection, resulting in the formation of dihydropyrenobisthieno[3,2-b]thiophene based octacyclic ladder-type donor core, which was flanked by two 1,1-dicyanomethylene-3-indanone (IC) acceptor motifs with and without 5,6-diflourination, namely PTT-IC and PTT-2FIC, respectively, as novel efficient A-D-A fused-ring electron acceptors (FREAs). Compared with PTT-IC, fluorinated PTT-2FIC possesses narrower optical bandgap of 1.48 eV, better π-π stacking, and its PBDB-T:PTT-2FIC blend film exhibited better morphology, and better hole and electron mobility. As a result, nonfullerene solar cells using PBDB-T:PTT-2FIC as the active layer achieved a decent PCE of 10.40%, with an open-circuit voltage (VOC) of 0.87 V, a fill factor (FF) of 0.65, and a much higher short-circuit current (JSC) of 18.26 mA/cm2. Meanwhile, the PBDB-T:PTT-IC cells delivered a lower JSC of 12.58 mA/cm2 but a higher VOC of 0.99 V, thus resulting in a PCE of 7.39% due to its wider optical bandgap of 1.58 eV and higher LUMO energy level. These results demonstrated that NFAs based on fused-ring donor core from fusing thieno[3,2-b]thiophenes with naphthalene via six-member-ring connection are promising for organic photovoltaic applications.
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| 14. |
- Fan, Qunping, et al.
(författare)
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10.13% Efficiency All-Polymer Solar Cells Enabled by Improving the Optical Absorption of Polymer Acceptors
- 2020
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Ingår i: Solar RRL. - : Wiley. - 2367-198X. ; 4:6
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Tidskriftsartikel (refereegranskat)abstract
- The limited light absorption capacity for most polymer acceptors hinders the improvement of the power conversion efficiency (PCE) of all-polymer solar cells (all-PSCs). Herein, by simultaneously increasing the conjugation of the acceptor unit and enhancing the electron-donating ability of the donor unit, a novel narrow-bandgap polymer acceptor PF3-DTCO based on an A–D–A-structured acceptor unit ITIC16 and a carbon–oxygen (C–O)-bridged donor unit DTCO is developed. The extended conjugation of the acceptor units from IDIC16 to ITIC16 results in a red-shifted absorption spectrum and improved absorption coefficient without significant reduction of the lowest unoccupied molecular orbital energy level. Moreover, in addition to further broadening the absorption spectrum by the enhanced intramolecular charge transfer effect, the introduction of C–O bridges into the donor unit improves the absorption coefficient and electron mobility, as well as optimizes the morphology and molecular order of active layers. As a result, the PF3-DTCO achieves a higher PCE of 10.13% with a higher short-circuit current density (Jsc) of 15.75 mA cm−2 in all-PSCs compared with its original polymer acceptor PF2-DTC (PCE = 8.95% and Jsc = 13.82 mA cm−2). Herein, a promising method is provided to construct high-performance polymer acceptors with excellent optical absorption for efficient all-PSCs.
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| 15. |
- Genene, Zewdneh, 1983, et al.
(författare)
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A comparative study of the photovoltaic performances of terpolymers and ternary systems
- 2017
-
Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 7:29, s. 17959-17967
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Tidskriftsartikel (refereegranskat)abstract
- Random terpolymers were synthesized from the electron-rich unit thiophene as the donor and two electron-deficient units with complementary absorption as the acceptor. Polymer solar cells (PSCs) fabricated from these terpolymers were compared with those fabricated from the ternary blends of two alternating polymers to explore the best strategy for extending the light absorption range. The two approaches showed similar open-circuit voltages (Voc) but different short-circuit current densities (Jsc). The terpolymer strategy broadened the light absorption range and provided a high power conversion efficiency (PCE) of 5.8%. This is due to a high Jsc and high hole mobility. The device fabricated from the ternary blend exhibited a lower PCE (3.5%) compared to those fabricated from the terpolymers and alternating polymer blends due to the morphological incompatibility of the donor polymers. Our results illustrate the potential of the terpolymer systems as a promising strategy to effectively increase the light absorption and thereby performance of PSCs by combining two morphologically incompatible polymers.
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| 16. |
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| 17. |
- Guo, Pengzhi, et al.
(författare)
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Twisted Alkylthiothien-2-yl Flanks and Extended Conjugation Length Synergistically Enhanced Photovoltaic Performance by Boosting Dielectric Constant and Carriers Kinetic Characteristics
- 2021
-
Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 222:12
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Tidskriftsartikel (refereegranskat)abstract
- Alternating conjugated polymers (CPs), derived from 2-ethylhexylthiothiophen-2-yl (TS) or 2-ethylhexylthiophen-2-yl (T) flanked dithieno[3,2-d:3,2-d ']benzo[1,2-b:4,5-b ']dithiophene (DTBDT) and diketopyrrolo-pyrrole (DPP) termed as PDTBDT-TS-DPP and PDTBDT-T-DPP, are prepared and characterized. It is found that the PDTBDT-TS-DPP not only exhibits slightly deepening the highest occupied molecular orbital energy levels, and similar absorption, etc., but also presents higher dielectric constant (epsilon(r)) of 6.7 at 1 kHz in contrast to 3.2 for PDTBDT-T-DPP, which are even higher than those of 4.3 and 3.0 for PBDT-TS-DPP/PBDT-T-DPP generated from TS and T flanked benzo[1,2-b:4,5-bMODIFIER LETTER PRIME]dithiophene and DPP. Beyond that, the power conversion efficiency of 8.17% for the inverted photovoltaic devices from DPP-based CPs, is achieved from PDTBDT-TS-DPP. The alkylthio side chains are used in the DTBDT of the larger twisting angles of TS flanks and longer conjugation length, synergistically contribute to the highest dipole moments, and then lead to the enhancement of epsilon(r), thus devoted the modification exciton dissociation and charge carriers kinetic characteristics. To the authors' knowledge, it is the first time to report that epsilon(r) of the CPs is connected with the twisting angle of flanks and conjugation length of the building blocks, besides the use of functional side chains and atoms.
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| 18. |
- Hou, Lintao, et al.
(författare)
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Lateral Phase Separation Gradients in Spin-Coated Thin Films of High-Performance Polymer: Fullerene Photovoltaic Blends
- 2011
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Ingår i: Advanced Functional Materials. - : Wiley. - 1616-3028 .- 1616-301X. ; 21:16, s. 3169-3175
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Tidskriftsartikel (refereegranskat)abstract
- In this study, it is demonstrated that a finer nanostructure produced under a rapid rate of solvent removal significantly improves charge separation in a high-performance polymer: fullerene bulk-heterojunction blend. During spin-coating, variations in solvent evaporation rate give rise to lateral phase separation gradients with the degree of coarseness decreasing away from the center of rotation. As a result, across spin-coated thin films the photocurrent at the first interference maximum varies as much as 25%, which is much larger than any optical effect. This is investigated by combining information on the surface morphology of the active layer imaged by atomic force microscopy, the 3D nanostructure imaged by electron tomography, film formation during the spin coating process imaged by optical interference and photocurrent generation distribution in devices imaged by a scanning light pulse technique. The observation that the nanostructure of organic photovoltaic blends can strongly vary across spin-coated thin films will aid the design of solvent mixtures suitable for high molecular-weight polymers and of coating techniques amenable to large area processing.
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| 19. |
- James, David, 1987, et al.
(författare)
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High-Performance Hole Transport and Quasi-Balanced Ambipolar OFETs Based on D–A–A Thieno-benzo-isoindigo Polymers
- 2016
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Ingår i: Advanced Electronic Materials. - : Wiley. - 2199-160X. ; 2:4
-
Tidskriftsartikel (refereegranskat)abstract
- Two new conjugated polymers are synthesized based on a novel donor–acceptor–acceptor (D–A–A) design strategy with the intention of attaining lower lowest unoccupied molecular obital levels compared to the normally used D–A strategy. By coupling two thieno-benzo-isoindigo units together via the phenyl position to give a new symmetric benzene-coupled di-thieno-benzo-isoindigo (BdiTBI) monomer as an A–A acceptor and thiophene (T) or bithiophene (2T) as a donor, two new polymers PT-BdiTBI and P2T-BdiTBI are synthesized via Stille coupling. The two polymers are tested in top gate and top contact field effect transistors, which exhibit balanced ambipolar charge transport properties with poly(methyl methacrylate) as dielectric and a high hole mobility up to 1.1 cm2 V–1 s–1 with poly(trifluoroethylene) as dielectric. The polymer films are investigated using atomic force microscopy, which shows fibrous features due to their high crystallinity as indicated by grazing incidence wide-angle X-ray scattering. The theoretical calculations agree well with the experimental data on the energy levels. It is demonstrated that the D–A–A strategy is very effective for designing low band gap polymers for organic electronic applications.
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| 20. |
- Li, Zhaojun, 1989, et al.
(författare)
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High-performance all-polymer solar cells based on fluorinated naphthalene diimide acceptor polymers with fine-tuned crystallinity and enhanced dielectric constants
- 2018
-
Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855. ; 45, s. 368-379
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Tidskriftsartikel (refereegranskat)abstract
- Growing interests have been devoted to the synthesis of polymer acceptors as alternatives to fullerene derivatives to realize high-performance and stable all-polymer solar cells (all-PSCs). So far, one of the key factors that limit the performance of all-PSCs is low photocurrent density (normally < 14 mA/cm 2 ). One potential solution is to improve the dielectric constants (ε r ) of polyme r :polymer blends, which tend to reduce the binding energy of excitons, thus boosting the exciton dissociation efficiencies. Nevertheless, the correlation between ε r and photovoltaic performance has been rarely investigated for all-PSCs. In this work, five fluorinated naphthalene diimide (NDI)-based acceptor polymers, with different content of fluorine were synthesized. The incorporation of fluorine increased the ε r of the acceptor polymers and blend films, which improved the charge generation and overall photocurrent of the all-PSCs. As a result, the PTB7-Th:PNDI-FT10 all-PSC attained a high power conversion efficiency (PCE) of 7.3% with a photocurrent density of 14.7 mA/cm 2 , which surpassed the values reported for the all-PSC based on the non-fluorinated acceptor PNDI-T10. Interestingly, similarly high photovoltaic performance was maintained regardless of a large variation of donor:acceptor ratios, which revealed the good morphological tolerance and the potential for robust production capability of all-PSCs.
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| 21. |
- Liu, Lihui, 1985, et al.
(författare)
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Substrate-dependent resistance decrease of graphene by ultraviolet-ozone charge doping
- 2016
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 6:67, s. 62091-62098
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Tidskriftsartikel (refereegranskat)abstract
- Large sheet resistance is the critical problem of graphene for application in electronic and optoelectronic devices as transparent electrodes. Ultraviolet/ozone (UVO) treatment is a convenient, highly effective, vacuum process and post-clean free method. This paper reveals that the effect of UVO treatment on the resistance of graphene is substrate dependent, which means that the band gap and photogenerated charge carriers of the substrates under UV illumination play a key role in the doping effect. The resistance of graphene can be decreased by as much as 80% on F8BT, GaN and PTFE substrates, by 70% on PMMA substrate, and by 50% on paraffin and glass substrates. Large band gap substrates (>hν) will induce a p-doping effect, while small band gap substrates (
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| 22. |
- Liu, Shungang, et al.
(författare)
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The role of connectivity in significant bandgap narrowing for fused-pyrene based non-fullerene acceptors toward high-efficiency organic solar cells
- 2020
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 8:12, s. 5995-6003
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Tidskriftsartikel (refereegranskat)abstract
- Great attention has been paid to developing low bandgap non-fullerene acceptors (NFAs) for matching wide bandgap donor polymers to increase the photocurrent and therefore the power conversion efficiencies (PCEs) of NFA organic solar cells, while pyrene-core based acceptor-donor-acceptor (A-D-A) NFAs have been mainly reported via the 2,9-position connection due to their bisthieno[3′,2′-b']thienyl[a,h]pyrene fused via a five-membered ring bridge at the ortho-position of pyrene as the representative one named FPIC5, which has prohibited further narrowing their energy gap. Herein, an acceptor FPIC6 was exploited by creating the 1,8-position connection through fusing as bisthieno[3′,2′-b′]thienyl[f-g,m-n]pyrene linked at the bay-position via a six-membered bridge, with enhanced push-pull characteristics within such A-D-A structure. As a structural isomer of FPIC5, FPIC6 exhibited a much lower bandgap of 1.42 eV (1.63 eV for FPIC5). Therefore, the photocurrent and PCE of PTB7-Th:FPIC6 cells were improved to 21.50 mA cm-2 and 11.55%, respectively, due to the balanced mobilities, better photoluminescence quenching efficiency and optimized morphology, which are both ∼40% better than those of PTB7-Th:FPIC5 cells. Our results clearly proved that a pyrene fused core with 1,8-position connection with electron-withdrawing end groups instead of 2,9-position connection is an efficient molecular design strategy to narrow the optical bandgap and improve the photovoltaic performance of NFA based OSCs.
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| 23. |
- Liu, Yi, et al.
(författare)
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Effect of fluorine atoms on optoelectronic, aggregation and dielectric constants of 2,1,3-benzothiadiazole-based alternating conjugated polymers
- 2021
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Ingår i: Dyes and Pigments. - : Elsevier BV. - 0143-7208 .- 1873-3743. ; 193
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Tidskriftsartikel (refereegranskat)abstract
- Three 2,1,3-benzothiadiazole-based conjugated copolymers named PBDT-0F-BTs, PBDT-2F-BTs and PBDT-6F-FBTs, which were derived from 4,8-bis(4,5-dioctylthiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene and (3,4′-bis(2-hexyl- decyl)-2,2′-dithiophene-5-yl) substituted 2,1,3-benzothiadiazole and/or 5,6-difluoro- 2,1,3-benzothiadiazole derivatives with 2,2′-dithiophene and/or 3,3′-difluoro- 2,2′-dithiophene as π-linkers, were prepared and characterized. The copolymers PBDT-0F-BTs, PBDT-2F-BTs and PBDT-6F-FBTs exhibited the highest occupied molecular orbital (HOMO) and lowest unoccupied orbital (LUMO) energy levels of −5.38 eV/−3.57 eV, −5.45 eV/−3.65 eV and −5.55 eV/−3.78 eV, with the light response from 300 nm to 720–750 nm, alongside with the similar aggregation, except that the charge transporting mobilities were successively increased, and the dielectric constants were gradually improved from 3.3 to 4.8 to 5.9 at 1 KHz, while the fluorine atoms in the each repeat unit of polymers were varied from 0 to 2 and then up to 6, respectively. Beyond that, it has also been found that the power conversion efficiencies and exciton dissociation probability (P(E,T)) of the bulk heterojunction organic photovoltaic cells (BHJ-OPVs) from the blend films of polymers paired with Y6 (2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl12,13-dihydro[1,2,5]thia- diazolo[3,4-e]thieno[2'',3'':4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-ind-ene-2,1-diylidene))dimalononitrile), were varied from 7.83% and 85.9%, to 9.22% and 90.2% and then up to 12.34% and 91.4%. The results indicated that the continuous insertion of the fluorine atoms into the repeat units of the conjugated polymers would result in the consecutively deepening the HOMO energy levels, increase dielectric constants and charge mobilities, thus devote to the enhancement of the P(E,T) and the performance of the BHJ-OPVs.
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| 24. |
- Ma, Ruijie, et al.
(författare)
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All-polymer solar cells with over 16% efficiency and enhanced stability enabled by compatible solvent and polymer additives
- 2022
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Ingår i: Aggregate. - : Wiley. - 2692-4560 .- 2766-8541. ; 3:3
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Tidskriftsartikel (refereegranskat)abstract
- Considering the robust and stable nature of the active layers, advancing the power conversion efficiency (PCE) has long been the priority for all-polymer solar cells (all-PSCs). Despite the recent surge of PCE, the photovoltaic parameters of the state-of-the-art all-PSC still lag those of the polymer:small molecule-based devices. To compete with the counterparts, judicious modulation of the morphology and thus the device electrical properties are needed. It is difficult to improve all the parameters concurrently for the all-PSCs with advanced efficiency, and one increase is typically accompanied by the drop of the other(s). In this work, with the aids of the solvent additive (1-chloronaphthalene) and the n-type polymer additive (N2200), we can fine-tune the morphology of the active layer and demonstrate a 16.04% efficient all-PSC based on the PM6:PY-IT active layer. The grazing incidence wide-angle X-ray scattering measurements show that the shape of the crystallites can be altered, and the reshaped crystallites lead to enhanced and more balanced charge transport, reduced recombination, and suppressed energy loss, which lead to concurrently improved and device efficiency and stability.
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| 25. |
- Mone, Mariza, 1992, et al.
(författare)
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Near-Infrared Emission by Tuned Aggregation of a Porphyrin Compound in a Host–Guest Light-Emitting Electrochemical Cell
- 2021
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Ingår i: Advanced Optical Materials. - : Wiley. - 2195-1071 .- 2162-7568. ; 9:6
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of 5,10,15,20-tetrakis((5,10-bis((2-hexyldecyl)oxy)dithieno[3,2-c:3′,2′-h][1,5]naphthyridin-2-yl)ethynyl)porphyrin zinc(II) (Por4NT), a near-infrared (NIR) emitting compound, comprising a zinc porphyrin core linked with triple bonds through its meso positions to four 5,10-bis((2-hexyldecyl)oxy)dithieno[3,2-c:3′,2′-h][1,5]naphthyridine (NT) arms is reported. Por4NT featured high solubility in common non-polar solvents, which is ideal for easy processing through solution techniques, and high photoluminescence (PL) efficiency of ≈30% in dilute toluene solution. It also exhibited a strong tendency for aggregation because of its flat conformation, and this aggregation resulted in a strong redshifted emission and a drop in PL efficiency. A well-matched PBDTSi-BDD-Py “host” terpolymer is therefore designed, which is capable of mitigating the aggregation of the Por4NT “guest”. An optimized blend of the host, guest, and an ionic-liquid electrolyte is utilized as the active material in a light-emitting electrochemical cell (LEC), which delivered strong NIR radiance of 134 µW cm-2 with a long wavelength maximum at 810 nm at a low drive voltage of 5.0 V. The attainment of the strong NIR emission from the host–guest LEC is attributed to a tuned aggregation of the Por4NT emitter, which resulted in the desired aggregation-induced redshift of the emission at a reasonably retained efficiency.
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