| 1. |
- Alkadir Abdulahi, Birhan, 1985, et al.
(författare)
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Structural engineering of pyrrolo[3,4-: F] benzotriazole-5,7(2 H,6 H)-dione-based polymers for non-fullerene organic solar cells with an efficiency over 12%
- 2019
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 7:33, s. 19522-19530
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we have synthesized two wide band gap donor polymers based on benzo[1,2-b:4,5-b′]dithiophene (BDT) and pyrrolo[3,4-f]benzotriazole-5,7(2H,6H)-dione (TzBI), namely, PBDT-TzBI and PBDT-F-TzBI and studied their photovoltaic properties by blending them with ITIC as an acceptor. Polymer solar cell devices made from PBDT-TzBI:ITIC and PBDT-F-TzBI:ITIC exhibited power conversion efficiencies (PCEs) of 9.22% and 11.02% and while annealing at 160 °C, improved the device performances to 10.24% and 11.98%, respectively. Upon solvent annealing with diphenyl ether (DPE) (0.5%) and chlorobenzene (CB), the PCE of the PBDT-F-TzBI-based device increased to 12.12%. The introduction of the fluorinated benzodithiophene (BDT-F) moiety on the backbone of PBDT-F-TzBI improved the open circuit voltage, short circuit current and fill factor simultaneously. The high PCEs of the PBDT-F-TzBI:ITIC-based devices were supported by comparison and analysis of the optical and electronic properties, the charge carrier mobilities, exciton dissociation probabilities, and charge recombination behaviors of the devices.
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| 2. |
- Bergqvist, J., et al.
(författare)
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Sub-glass transition annealing enhances polymer solar cell performance
- 2014
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Ingår i: Journal of Materials Chemistry A. - 2050-7488 .- 2050-7496. ; 2:17, s. 6146-6152
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Tidskriftsartikel (refereegranskat)abstract
- Thermal annealing of non-crystalline polymer:fullerene blends typically results in a drastic decrease in solar cell performance. In particular aggressive annealing above the glass transition temperature results in a detrimental coarsening of the blend nanostructure. We demonstrate that mild annealing below the glass transition temperature is a viable avenue to control the nanostructure of a non-crystalline thiophene–quinoxaline copolymer:fullerene blend. Direct imaging methods indicate that coarsening of the blend nanostructure can be avoided. However, a combination of absorption and luminescence spectroscopy reveals that local changes in the polymer conformation as well as limited fullerene aggregation are permitted to occur. As a result, we are able to optimise the solar cell performance evenly across different positions of the coated area, which is a necessary criterion for large-scale, high throughput production.
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| 3. |
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| 4. |
- Li, Zhaojun, 1989, et al.
(författare)
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High-photovoltage all-polymer solar cells based on a diketopyrrolopyrrole-isoindigo acceptor polymer
- 2017
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 5:23, s. 11693-11700
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we synthesized and characterized two new n-type polymers PTDPP-PyDPP and PIID-PyDPP. The former polymer is composed of pyridine-flanked diketopyrrolopyrrole (PyDPP) and thiophene-flanked diketopyrrolopyrrole (TDPP). The latter polymer consists of PyDPP and isoindigo (IID). PIID-PyDPP exhibits a much higher absorption coefficient compared to the widely used naphthalene diimide (NDI)-based acceptor polymers, and its high-lying LUMO level affords it to achieve a high open-circuit voltage (Voc). As a result, an all-polymer solar cell (all-PSC) fabricated from a high band gap polymer PBDTTS-FTAZ as the donor and PIID-PyDPP as the acceptor attained a high Voc of 1.07 V with a power conversion efficiency (PCE) of 4.2%. So far, it has been one of the highest PCEs recorded from all-PSCs using diketopyrrolopyrrole (DPP)-based acceptors. Gratifyingly, no obvious PCE decay was observed in two weeks, unraveling good stability of the all-PSC. This work demonstrates that the electron-withdrawing PyDPP unit can be a promising building block for new acceptor polymers in all-PSCs.
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| 5. |
- Lin, Y. B., et al.
(författare)
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Study of ITO-free roll-to-roll compatible polymer solar cells using the one-step doctor blading technique
- 2017
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 5:8, s. 4093-4102
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Tidskriftsartikel (refereegranskat)abstract
- Extremely simple one-step coating ITO-free inverted polymer solar cells (IFIPSCs) have been fabricated using a novel film deposition method-doctor blading technique, which is completely compatible with roll-to-roll (R2R) manufacturing. Delamination of the interfacial buffer layer (IBL) from the photoactive mixtures is achieved via a spontaneous vertical self-assembly. The performance of one-step doctor-blading IFIPSCs is primarily influenced by the inherent IBL stratification purity rather than the fine donor/acceptor phase separation for the rigid backbone PTB7 system, which is significantly different from that of the conventional two-step doctor blading devices. The surface energy results strongly demonstrate that the formation of the interfacial layer between the ITO-free cathode and the photoactive layer is significantly controlled by the solvent drying time, which determines the self-assembly quality and can be greatly manipulated from 2700 to 1200 s by different substrate temperatures. It's worth noting that the pure interfacial layer formed at low substrate temperatures improves charge separation and transport, whereas high substrate temperatures limit its growth, leading to the decrease of device performance. The detailed relationship between the self-assembly interfacial layer and the internal resistance and capacitance is revealed by impedance spectroscopy. Encouraging power conversion efficiency (PCE) of 6.56% is achieved from simple one-step doctor-blading ITO-free devices at a very low substrate temperature of 25 degrees C, which is energy saving and appropriate for industrialized R2R production. In contrast, the highest PCE of 7.11% ever reported for two-step doctor-blading ITO-free IFIPSCs was obtained at a high substrate temperature of 60 degrees C for achieving a fine morphology without regard to the vertical delamination. Furthermore, for crystalline polymer systems like P3TI with a semiflexible chain, it requires a higher substrate temperature of 40 degrees C to mediate the balance of vertical selfassembly stratification of the interfacial buffer layer and photoactive morphology to maximize the device performance.
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| 6. |
- Lindqvist, Camilla, 1985, et al.
(författare)
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Nucleation-limited fullerene crystallisation in a polymer–fullerene bulk-heterojunction blend
- 2013
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Ingår i: Journal of Materials Chemistry A. - 2050-7488 .- 2050-7496. ; 1:24, s. 7174-7180
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Tidskriftsartikel (refereegranskat)abstract
- The nucleation and growth kinetics of fullerene crystals in thin films of a polymer:fullerene bulk-heterojunction blend are investigated. We find that both processes are strongly diffusion-limited at 100–110 °C due to the proximity to the glass transition temperatures of the blend components. Whereas the growth rate exponentially increases with temperature up to 230 °C, the nucleation rate displays a broad maximum around 150–170 °C, which coincides with the highest rate of fullerene crystallisation. A time-temperature-transformation (TTT) diagram reveals that across the investigated range of temperatures the low rate of nucleation is responsible for the formation of micrometre-sized crystals, which can be detrimental for polymer solar cells. Thus, we identify the lack of sufficient nucleation, which predominantly occurs on the substrate interface, as the origin of this important degradation mechanism.
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| 7. |
- 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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| 8. |
- Manca, M., et al.
(författare)
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Tracing charge transfer states in polymer:fullerene bulk-heterojunctions
- 2013
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 1:25, s. 7321-7325
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Tidskriftsartikel (refereegranskat)abstract
- Charge transfer state emission in organic bulk-heterojunctions has been demonstrated to be an important loss mechanism for this reason a better understanding of the nature and origin of the charge transfer state is fundamental for the improvement of organic solar cells. Here, the relationship between photophysical and morphological features of a prototypical organic bulk-heterojunction is investigated in blends with different donor-acceptor ratios. By correlating imaging with photoluminescence spectra measured in different areas of the blends, the charge transfer state emission is unambiguously assigned to microscopical regions in which the intermixing of the two organic semiconductors is higher.
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| 9. |
- Peng, Zuosheng, et al.
(författare)
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A dual ternary system for highly efficient ITO-free inverted polymer solar cells
- 2015
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 3:36, s. 18365-18371
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Tidskriftsartikel (refereegranskat)abstract
- In this study, it has been found that a very fine nanostructure can be realized by mixing 1-chloronaphthalene (CN) - a high-boiling solvent into a binary chlorobenzene (CB) : 1,8-diiodooctane (DIO) solvent mixture to form a ternary solvent system. An improvement in energy level alignment is also obtained by doping ICBA into a binary PTB7 : PCBM[70] blend, whereby the ternary solute system provides a new pathway for charge transfer from PTB7 to the PCBM[ 70] : ICBA alloy. This is confirmed by imaging the surface morphology of the active layer using AFM and TEM, monitoring the transient film formation process and measuring the charge transfer states with Fourier transform photocurrent spectroscopy. An encouraging PCE of 7.65% is achieved from the dual ternary system, which is the highest value ever reported for an ITO-free inverted polymer solar cell with a PEDOT:PSS layer as the top semitransparent electrode - a system which is compatible with low-cost large-area roll-to-roll manufacturing.
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| 10. |
- Shen, W. F., et al.
(författare)
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High-performance ternary polymer solar cells from a structurally similar polymer alloy
- 2017
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 5:24, s. 12400-12406
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Tidskriftsartikel (refereegranskat)abstract
- High-efficiency ternary polymer solar cells (PSCs) are fabricated by using two donor polymers (PBDTTPD and PBDTTT-C-T) with similar polymer backbones and complementary absorption and PC71BM as the acceptor. A high power conversion efficiency (PCE) of 9.3% is achieved with a high short-circuit current density (J(sc)) of 17.2 mA cm(-2). The enhanced J(sc) and PCEs are mainly attributed to the broadened photoresponse of the ternary blend. Good miscibility of the two donor polymers is found due to the similar polymer main chains, leading to the desired morphology between the donors and PC71BM in the ternary blends. The trend of open-circuit voltage (V-oc) variations indicates the formation of a polymer alloy in this ternary blend. Our work demonstrates that using two donor polymers with similar backbone structures is a rational strategy for realizing high-performance ternary PSCs.
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