| 1. |
- Gebremariam, Kidan G., et al.
(författare)
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Self-Assembled Monolayer Engineered ZnO Electron Transport Layer to Improve the Photostability of Organic Solar Cells
- 2024
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Ingår i: Energy & Fuels. - 1520-5029 .- 0887-0624. ; 38:14, s. 13304-13314
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Tidskriftsartikel (refereegranskat)abstract
- The degradation of organic solar cells (OSCs) can occur in any of the layers, underlining the importance of each layer in prolonging their lifetime. To enhance the performance and stability of inverted OSCs (i-OSCs), interfacial modification has been employed. In this context, two self-assembled monolayers (SAMs), namely, octadecanthiol (ODT) and octadecyltrimethoxysilane (OTMS), were utilized to effectively passivate typical surface defects in the ZnO electron transport layer (ETL). The SAM-treated ZnO films were found to be more hydrophobic, which reduced surface defects produced by adsorbed oxygen and hydroxyl groups. Consequently, the power conversion efficiency (PCE) of the i-OSCs comprising an indacenodithieno[3,2-b]thiophene-alt-5,5-di(thiophen-2-yl)-2,2-bithiazole (PIDTT-DTBTz) donor blended with [6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) acceptor increased from 4.20% in pristine ZnO- to 5.01 and 5.37% in ODT- and OTMS-treated ZnO-based devices, respectively. In addition, the photostability of the device substantially improved. Hence, devices based on ZnO treated with ODT and OTMS kept 76 and 89% of their initial PCE, respectively, while pristine ZnO-based devices retained only 66% of the initial PCE after 48 h of irradiation. The improved PCE and extended lifetime of the i-OSCs can be attributed to enhanced charge transfer, the reduction in both bimolecular and trap-assisted recombination processes, and the enhanced interface between the ETL and the active layer. Moreover, it has been observed that the OTMS-treated ZnO ETL-based i-OSC offers better stability and more efficient devices compared to the ODT-treated ZnO ETL-based devices. This can be attributed to the favorable dipole moment generated by the increased electrostatic potential at the anchor group, which promotes improved device performance.
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| 2. |
- Wolkeba, Zewdneh Genene, 1983, et al.
(författare)
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Recent Advances in the Synthesis of Conjugated Polymers for Supercapacitors
- 2024
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Ingår i: Advanced Materials Technologies. - 2365-709X. ; 9:9
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Forskningsöversikt (refereegranskat)abstract
- Conjugated polymers have attracted growing attention for versatile applications in energy storage due to their potential benefits including low-cost processing, molecular tunability, environmental benignity, and high mechanical flexibility. In particular, polymer-based organic electrode materials have shown significant progress in supercapacitor (SC) applications with superior electrochemical behaviors. The performances of SCs are closely related to the intrinsic characteristics of different polymers in the nanoscale and the morphological features of the polymer-based electrode materials obtained by different fabrication techniques in the macroscale. This review summarizes the design and synthesis of both p-type and n-type conjugated polymers, highlighting the pros and cons of three synthesis techniques: electrochemical polymerization, chemical polymerization, and in situ polymerization. The performances of conjugated polymers in SCs, their cycling stabilities, and structure-performance relationships are discussed. Moreover, the existing challenges and future directions of polymer-based SCs are considered with respect to energy density, stability, and large-scale production to promote commercialization.
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| 3. |
- Aich, Pijush Kanti, et al.
(författare)
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Enhancement of Photosensitivity in a Low-Operating-Voltage Organic-Inorganic Bilayer Thin-Film Transistor by Using an Asymmetric Source-Drain Electrode
- 2024
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Ingår i: ACS Photonics. - 2330-4022. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- A solution-processed inorganic-organic bilayer semiconductor channel-based red-light-sensitive thin-film transistor (TFT) has been fabricated by using an ion-conducting Li-Al2O3 gate dielectric that limits the operating voltage of this TFT within 2 V. In this device, a high-electron-mobility inorganic metal-oxide semiconductor (SnO2) was used as the primary charge transport layer, whereas the polymer (PIDT-2TPD) was used as the photoactive layer. To improve its red photosensitivity, an asymmetric work function source-drain (S-D) electrode was fabricated, which allows a selective carrier (electron or hole) injection and collection from the channel. Besides, the work function difference of this asymmetric S-D electrode generates a potential difference between electrodes that allows faster charge collection from the channel. As a consequence, the photosensitivity of this asymmetric S-D electrode TFT enhanced by ∼103 times under red illumination with respect to the symmetric S-D electrode TFT and the detectivity of this device increased ∼20 times. In addition, the on/off ratio of asymmetric TFT is 4 times greater than that of the symmetric TFT, whereas the subthreshold swing (SS) of this TFT is reduced from 200 to 144 mV/decade.
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| 4. |
- Filate, Tadele Tamenu, 1994, et al.
(författare)
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Aqueous Processed All-Polymer Solar Cells with High Open-Circuit Voltage Based on Low-Cost Thiophene-Quinoxaline Polymers
- 2024
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Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8252 .- 1944-8244. ; 16:10, s. 12886-12896
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Tidskriftsartikel (refereegranskat)abstract
- Eco-friendly solution processing and the low-cost synthesis of photoactive materials are important requirements for the commercialization of organic solar cells (OSCs). Although varieties of aqueous-soluble acceptors have been developed, the availability of aqueous-processable polymer donors remains quite limited. In particular, the generally shallow highest occupied molecular orbital (HOMO) energy levels of existing polymer donors limit further increases in the power conversion efficiency (PCE). Here, we design and synthesize two water/alcohol-processable polymer donors, poly[(thiophene-2,5-diyl)-alt-(2-((13-(2,5,8,11-tetraoxadodecyl)-2,5,8,11-tetraoxatetradecan-14-yl)oxy)-6,7-difluoroquinoxaline-5,8-diyl)] (P(Qx8O-T)) and poly[(selenophene-2,5-diyl)-alt-(2-((13-(2,5,8,11-tetraoxadodecyl)-2,5,8,11-tetraoxatetradecan-14-yl)oxy)-6,7-difluoroquinoxaline-5,8-diyl)] (P(Qx8O-Se)) with oligo(ethylene glycol) (OEG) side chains, having deep HOMO energy levels (∼−5.4 eV). The synthesis of the polymers is achieved in a few synthetic and purification steps at reduced cost. The theoretical calculations uncover that the dielectric environmental variations are responsible for the observed band gap lowering in OEG-based polymers compared to their alkylated counterparts. Notably, the aqueous-processed all-polymer solar cells (aq-APSCs) based on P(Qx8O-T) and poly[(N,N′-bis(3-(2-(2-(2-methoxyethoxy)-ethoxy)ethoxy)-2-((2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-methyl)propyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl)-alt-(2,5-thiophene)] (P(NDIDEG-T)) active layer exhibit a PCE of 2.27% and high open-circuit voltage (VOC) approaching 0.8 V, which are among the highest values for aq-APSCs reported to date. This study provides important clues for the design of low-cost, aqueous-processable polymer donors and the fabrication of aqueous-processable OSCs with high VOC
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| 5. |
- Filate, Tadele Tamenu, 1994, et al.
(författare)
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Hydrophilic Conjugated Polymers for Sustainable Fabrication of Deep-Red Light-Emitting Electrochemical Cells
- 2024
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Ingår i: Advanced Materials Technologies. - : John Wiley & Sons. - 2365-709X. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- It is crucial to develop functional electronic materials that can be processed from green solvents to achieve environmentally sustainable and cost-efficient printing fabrication of organic electronic devices. Here, the design and cost-efficient synthesis of two hydrophilic and emissive conjugated polymers, TQ-OEG and TQ2F-OEG, are presented, which are rendered hydrophilic through the grafting of oligo(ethylene glycol) (OEG) solubilizing groups onto the thiophene-quinoxaline conjugated backbone and thereby can be processed from a water:ethanol solvent mixture. It is shown that the introduction of the OEG groups enables for a direct dissolution of salts by the neat polymer for the attainment of solid-state ion mobility. These properties are utilized for the design and development of light-emitting electrochemical cells (LECs), the active materials of which can be solution cast from a water:ethanol-based ink. It is specifically shown that such an LEC device, comprising an optimized blend of the TQ2F-OEG emitter and a Li salt as the active material positioned between two air-stabile electrodes, delivers deep-red emission (peak wavelength = 670 nm) with a radiance of 185 µW m−2 at a low drive voltage of 2.3 V. This study contributes relevant information as to how polymers and LEC devices can be designed and fabricated to combine functionality with sustainability.
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| 6. |
- Nchinda, Leonato Tambua, et al.
(författare)
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Unveiling the thermal stability of diketopyrrolopyrrole-based terpolymers: a key element for enhanced efficiency and stability of organic solar cells
- 2024
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Ingår i: New Journal of Chemistry. - 1369-9261 .- 1144-0546. ; 48:22, s. 10201-10212
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Tidskriftsartikel (refereegranskat)abstract
- With the advent of novel polymers, organic solar cell (OSC) research has evolved significantly over the past decade. The molecular engineering of terpolymers has allowed for simple morphological control in binary devices over ternary blends, with the highest power conversion efficiencies (PCEs) exceeding 18%. However, research on the stability of OSCs is still lagging behind. In this regard, we examined the thermal stability of a series of terpolymers comprising one electron donor (thienyl-substituted benzodithiophene, BDTT) and two types of electron acceptors namely fluorobenzotriazole (FTAZ) and thienothiophene-capped diketopyrrolopyrrole (TTDPP) and their blends with PC71BM. The terpolymers demonstrated broad absorbance ranging from below 350 nm to 900 nm. The thermal stability of the terpolymers was investigated as pristine thin films and as bulk heterojunction (BHJ) films of the terpolymers blended with PC71BM by heating at 85 °C. We observed that thermal degradation had no sizeable effect on the properties of the pristine terpolymers while the blended films demonstrated significant changes in their morphology due to the inclusion and aggregation of PC71BM. After thermal annealing at 85 °C, the width of the symmetric C=C stretching Raman mode and the C=C/C-C intensity ratio of pristine terpolymers and terpolymer:PC71BM thin films revealed that incorporation of the FTAZ acceptor improves the thermal stability of the BHJ active layers. Furthermore, prolonged thermal annealing times (>3 hours) resulted in the development of PC71BM aggregates and terpolymer decomposition with no evident changes in the molecular and chemical structure of the terpolymers. Our findings indicate that by gradually annealing the blended films using an appropriate annealing time, the diffusion of PC71BM molecules to form aggregates can be carefully regulated, resulting in a nanostructure critical to the efficiency of organic solar cells.
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| 7. |
- Negash, Asfaw, et al.
(författare)
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Exploring the High-Temperature Window of Operation for Organic Photovoltaics: A Combined Experimental and Simulations Study
- 2024
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Ingår i: Advanced Materials for Optics and Electronics. - 1616-301X .- 1616-3028. ; 34:6
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Tidskriftsartikel (refereegranskat)abstract
- The global climate change negatively affects the photovoltaic performance of traditional solar cell technologies. This article investigates the potential of organic photovoltaics (OPV) for high-temperature environments, ranging from urban hot summers (30—40 °C) and desert regions (65 °C) up to (aero) space conditions (130 °C), the thermal window in which OPV can operate. The approach is based on a combination of experiments and simulations up to 180 °C, moving significantly beyond the conventional temperature ranges reported in the literature. New 2H-benzo[d][1,2,3]triazole-5,6-dicarboxylic imide-based copolymers with decomposition onset temperatures above 340 °C are used for this study, in combination with non-fullerene acceptors. Contrary to their inorganic counterparts, OPV devices show a positive temperature coefficient up to ≈90 °C. At temperatures of 150 °C, they are still operational, retaining their room temperature efficiency. Complementary simulations are performed using an in-house developed software package that numerically solves the drift-diffusion equations to understand the general trends in the obtained current–voltage characteristics and the materials’ intrinsic behavior as a function of temperature. The presented methodology of combined high-temperature experiments and simulations can be further applied to investigate the thermal window of operation for other OPV material systems, opening novel high-temperature application routes.
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| 8. |
- Xiang, Jiale, et al.
(författare)
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In situ monitoring drying process to disclose the correlation between the molecular weights of a polymer acceptor with a flexible spacer and the performance of all-polymer solar cells
- 2024
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Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7534 .- 2050-7526. ; 12:33, s. 13029-13039
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Tidskriftsartikel (refereegranskat)abstract
- Molecular weight (Mn) and conjugation of polymers can profoundly influence the performance of all-polymer solar cells (all-PSCs) via nanostructures of bulk heterojunctions (BHJs). To study the correlation between Mn and the performance of all-PSCs based on an acceptor with a flexible conjugation-break spacer (FCBS), three batches of acceptors, named PYTS, were synthesized with different number-average Mn from 9, 13 to 19 kDa. Blends with a polymer donor PBDB-T, the all-PSCs based on PYTS with Mn of 9 kDa and 19 kDa, exhibit power conversion efficiencies (PCEs) of 5.99% and 9.43%, respectively, primarily due to the increased short-circuit current density (Jsc) from 13.02 to 18.73 mA cm−2. To disclose the impact of Mn on device performance, dynamics of mixed PBDB-T:PYTS solutions to solid BHJs is studied by monitoring the drying process with home-made in situ multifunctional spectroscopy, which demonstrates that PYTS with Mn of 19 kDa has a longer drying time than the PYTS with Mn of 9 kDa. Prolonged drying of the BHJs with higher Mn PYTS facilitates more tightly packed structures with higher crystallinity. A systematic investigation on the nanostructures of BHJs, charge generation, transport and recombination is carried out with grazing-incidence wide-angle X-ray scattering (GIWAXS), transient absorption spectroscopy (TAS) and characterization of all-PSCs. The results indicate that increased crystallinity in the BHJs benefits exciton dissociation, electron transport, prolonged carrier lifetimes, and decreased non-geminate recombination rate constants in the corresponding devices. Combining the in situ study of drying and the investigation on films and devices provides us a comprehensive understanding of the interplay between Mn, the drying process, the nanostructures of BHJs and device performance. This work not only emphasizes the essential role of Mn in governing the device performance, but also exhibits recorded film formation through the in situ spectroscopy, enabling us to manipulate the nanostructure of BHJs by optimizing Mn of polymers and processing parameters.
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| 9. |
- 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
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Ingår i: Small. - 1613-6810 .- 1613-6829. ; In Press
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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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