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Effects of Short‐Axis Alkoxy Substituents on Molecular Self‐Assembly and Photovoltaic Performance of Indacenodithiophene‐Based Acceptors
摘要： The effects of central alkoxy side chain length of a series of narrow bandgap small molecule acceptors (SMAs) on their physicochemical properties and on the photovoltaic performance of the SMA-based polymer solar cells (PSCs) are systematically investigated. It is found that the ordered aggregation of these SMAs in films is enhanced gradually with the increase of alkoxy chain length. The single-crystal structures of these SMAs further reveal that small changes in the side chain length can have a dramatic impact on molecular self-assembly. The short-circuit current density and power conversion efficiency values of the corresponding PSCs increase with the increase of the side chain length of the SMAs. The π–π coherence length of the SMAs in the active layers is increased with the increase of the side chain length, which could be the reason for the increase of the Jsc in the PSCs. The results indicate that small changes in side chain length can have a dramatic impact on the molecular self-assembly, morphology, and photovoltaic performance of the PSCs. The structure–performance relationship established in this study can provide important instructions for the side chain engineering and for the design of efficient SMAs materials.
关键词： polymer solar cells,side chain engineering,morphology,small molecule acceptors,molecular self-assembly
更新于2025-09-19 17:13:59
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D-A Copolymer Donor Based on Bithienyl Benzodithiophene D-unit and Monoalkoxy Bifluoroquinoxaline A-unit for High Performance Polymer Solar Cells
摘要： Molecular frontier orbital energy level and aggregation behavior regulation of polymer donors are feasible way to improve the photovoltaic performance of polymer solar cells (PSCs). Here, we design and synthesize a new D-A copolymer donor PBQ10 based on bithienyl benzodithiophene D-unit and monoalkoxy-substituted bifluoroquinoxaline A-unit, which shows obviously down-shifted highest occupied molecular orbital energy level in comparison with the control polymer PBQ7 with dialkoxyphenyl substituent on the bifluoroquinoxaline A-unit. Moreover, PBQ10 exhibits more preferential face-on molecular orientation and tighter π–π stacking in the vertical direction of substrate than that of PBQ7, which significantly improves the hole mobility of PBQ10 to 5.22×10-4 cm2 V-1 s-1 in comparison with that (1.71×10-4 cm2 V-1 s-1) of PBQ7. As a result, the PBQ10-based PSC with Y6 as acceptor demonstrates an impressive power conversion efficiency (PCE) of 16.34 % with simultaneously increased open circuit voltage and fill factor, which is significantly increased than the PBQ7-based PSC with PCE of 13.45 %, and is one of the highest PCEs in binary PSCs. The result suggests that rational side chain optimization of polymer donor is an efficient way to regulate molecular energy level and self-assembly feature, thus to improve the PCE of PSCs.
关键词： Power conversion efficiency,Polymer solar cells,Bithienyl benzodithiophene,Monoalkoxy-substituted bifluoroquinoxaline,D-A copolymer donor
更新于2025-09-19 17:13:59
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Highly Efficient Large Area Organic Photovoltaic Module with 350 nm Thick Active Layer using Random Terpolymer Donor
摘要： Random terpolymers are developed by incorporating small portions of benzodithiophene into a highly crystalline copolymer of terthiophene and difluorobenzothiadiazole, BDT-Th0. The bulk-heterojunction (BHJ) of the copolymer BDT-Th0 is formed by process of rapid solid-liquid phase demixing of polymer crystallites, which results in irregular and unclear phase separation with large polymer aggregation. By contrast, the random terpolymer BDT-Th10 which was prepared using 10% feed molar ratio of a benzodithiophene moiety shows slower and gradual formation of the polymer packing structures without substantial agglomeration from loosely packed pseudo-crystallites in precursor solution. This results in optimal BHJ morphology with appropriate phase separation and improved domain purity. BDT-Th10 achieves high solar cell efficiency of 7.74% by successfully reproducing the optimized BHJ morphology of small cells into 58.5 cm2 sized modules with 350 nm film thickness, whereas the copolymer shows irreproducible property with much decreased efficiency of 4.37%. This result is among the highest efficiency of high-performance large area PSC modules with such a thick active film.
关键词： Random terpolymers,benzodithiophene,bulk-heterojunction,large area modules,polymer solar cells
更新于2025-09-19 17:13:59
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Effect of polymer donor aggregation on active layer morphology of amorphous polymer acceptor-based all-polymer solar cells
摘要： Most of polymer acceptors for all-polymer solar cells (all-PSCs) are semi-crystalline. Amorphous polymer acceptors containing B←N unit represent a new kind of acceptor materials and possess unique phase separation behaviours in all-PSCs. In this work, to study their phase separation morphology and all-PSC device performance, we select three polymer donors with identical polymer backbone but different side chains to blend with an amorphous polymer acceptor (rr-PBN). Among the three polymer donors, J91 exhibits the strongest aggregation tendency in solution and moderate crystallinity in thin film. The J91:rr-PBN blend shows the most optimal phase separation morphology and the best all-PSC device performance. In comparison, J51 shows the least aggregation tendency in solution and the highest crystallinity in thin film. The all-PSC device of J51:rr-PBN blend exhibits sub-optimal active layer morphology and poor photovoltaic performance. These results indicate that the aggregation tendency in solution of polymer donor is the dominant factor in the phase separation of semi-crystalline polymer donor/amorphous polymer acceptor blend in all-PSCs.
关键词： crystallinity,morphology,all-polymer solar cells,aggregation in solution,phase separation
更新于2025-09-19 17:13:59
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PCE11-based polymer solar cells with high efficiency over 13% achieved by room-temperature processing
摘要： With the emergence and rapid development of new non-fullerene acceptors (NFAs), bulk-heterojunction polymer solar cells (BHJ-PSCs) have achieved high power conversion efficiencies (PCEs) over 16%. Developing effective methods to fabricate high-performance thick-film PSCs is important to meet the requirements of the future roll-to-roll commercial production. PffBT4T-2OD (PCE11) as the most promising temperature-dependent aggregation (TDA) donor with high crystallinity has achieved high performance at high film thickness, which, however, needs at high processing temperature and is detrimental for practical production of large-area PSCs. We designed NFAs, ZITI-N-CH3, ZITI-N-C8H17, and ZITI-N-EH containing different side chains. Because of the excellent miscibility of the TDA-polymer PffBT4T-2OD and ZITI-N-R, the devices can be fabricated at room temperature, achieving a medium PCE of 8.78% for ZITI-N-CH3-based PSC, a high PCE of 12.13% for ZITI-N-C8H17-based PSC and a superior PCE of 13.07% for ZITI-N-EH-based PSC, which is attributed to the smallest domain size and highest crystallization for PffBT4T-2OD:ZITI-N-EH blend. The PCE of 13.07% is the highest among the TDA polymer-based PSCs, which can be maintained at 12.35% at the high thickness of 200 nm. This work provides an important guideline to develop high-performance thick-film TDA-polymer-based non-fullerene PSCs at mild processing conditions.
关键词： temperature-dependent aggregation,room-temperature processing,polymer solar cells,high efficiency,non-fullerene acceptors
更新于2025-09-19 17:13:59
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Enhancement the photovoltaic performance of conjugated polymer based on simple head-to-head alkylthio side chains engineered bithiophene
摘要： In this article, three novel and simple molecular structure with donor-acceptor (D-A) type copolymers via only head-to-head alkoxy (OR) and/or alkylthio (SR) side chains onto the bithiophene (BT) as donor units and fluorinated benzotriazole (FBTA) as acceptor unit, namely, PBTOR-FBTA, PBTOSR-FBTA and PBTSR-FBTA, were successfully designed and synthesized. The impacts of sulfur-oxygen (S???O) or sulfur-sulfur (S???S) noncovalent interactions on their physicochemical properties, molecular stacking, carrier mobility, morphologies of blend films, as well as their photovoltaic performance were deeply and systematically studied. The introduction of SR side-chains suddenly lowered the highest occupied molecular orbital (HOMO) energy levels, blue-shifted absorption, enhanced π-π stacking, as well as improved morphology of the photoactive layer blends in comparison with the reference polymer without SR side-chain. Polymer solar cells (PSCs) were fabricated to estimate their photovoltaic performance of the polymers. Under an optimized blend ratio of PBTSR-FBTA:PC71BM (1:0.8, w/w), the PBTSR-FBTA-based device exhibits a higher power conversion efficiency (PCE) of 6.25%, which is about 3.34 and 1.87 folds than that of the PBTOR-FBTA and PBTOSR-FBTA-based devices, respectively. Our research results demonstrate that the modification of the simple and low-cost SR side chains is an effective strategy to improve the photovoltaic performance of the polymers.
关键词： Alkoxy side chain,Fuorobenzotriazole,Polymer solar cells,Bithiophene,Alkylthio side chain
更新于2025-09-19 17:13:59
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A Random Polymer Donor for High-Performance Polymer Solar Cells with Efficiency Over 14%
摘要： Constructing random copolymers has been regarded as an easy and effective approach to design polymer donors for state-of-the-art polymer solar cells (PSCs). In this work, we develop a naphtho[2,3-c]thiophene-4,9-dione (NTDO) based copolymer PBN-Cl as a donor material for PSC, and a moderate power conversion efficiency (PCE) of 11.21% is achieved with a relatively low fill factor (FF) of 0.615. We then incorporate a similar acceptor unit benzo[1,2-c:4,5-c′]dithiophene-4,8-dione (BDD) into the polymeric backbone of PBN-Cl to tune its photovoltaic performance, and a significantly higher PCE of 14.05% is achieved from the random polymer PBN-Cl-B80 containing 80% BDD unit. The enhanced PCE of the PBN-Cl-B80-based device mainly relies on the higher FF value, resulting from the improved charge mobility properties, reduced bimolecular and trap-assisted recombination, and more appropriate phase separation. The results demonstrate a feasible strategy to tune the photovoltaic performance of polymer donors by constructing random polymer with a compatible component.
关键词： polymer solar cells,power conversion efficiency,random polymer,fill factor,charge-carrier mobility,polymer donor
更新于2025-09-16 10:30:52
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Positive effects of side-chain fluorination and polymer additive SBS on the enhanced performance of asymmetric-indenothiophene-based polymer solar cells
摘要： Two new D-A type photovoltaic polymers, namely PITPh-DfQx and PITPhf-DfQx, based on asymmetric indenothiophene (IT) donor units with alkoxyphenyl or fluoroalkoxyphenyl substitutes were designed and synthesized. Effects of the fluorine substitution in the asymmetric IT donor units on the electronic structure, ordering structure, photovoltaic properties, and charge generation and recombination dynamics were investigated. It is found that side-chain fluorination in the asymmetric donor units of the D-A polymers endowed the relative polymers with a deeper HOMO level, higher and more balanced charge mobilites, increased charge dissociation efficiency and reduced bimolecular recombination. As a result, the bulk heterojunction solar cell based on the blend film of PITPhf-DfQx and PC71BM demonstrated an efficiency of 6.10%, whereas the cell efficiency based on PITPh-DfQx was only 3.00%. In addition, a triblock copolymer, poly(styrene-block-butadiene-block-styrene) (SBS), was employed for the first time as a polymer additive into the active layers based on PITPh-DfQx/PC71BM and PITPhf-DfQx/PC71BM devices to promote donor crystallization and tune the extent of phase separation between the donor and acceptor. The presence of SBS obviously improved the molecule packing and induced the crystallization of the two polymers, giving rise to a better phase separation due to enhanced aggregation effect of photovoltaic polymers. Therefore, with a small addition of SBS, the optimal PCE was further increased from 6.10% to 6.60% for PITPhf-DfQx based device and from 3.00% to 5.50% for PITPh-DfQx based device. The positive effects of SBS additive on the performance of photovoltaic polymer/fullerene BHJ solar cells provide a new strategy for developing high performance polymer solar cells.
关键词： Morphology,Polymer additive SBS,Charge transport,Side-chain fluorination,Polymer solar cells,Asymmetric-indenothiophene
更新于2025-09-16 10:30:52
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High-efficiency non-halogenated solvent processable polymer/PCBM solar cells <i>via</i> fluorination-enabled optimized nanoscale morphology
摘要： PNTz4T-based polymers have been extensively employed in high-efficiency fullerene-based polymer solar cells (PSCs) with a power conversion efficiency (PCE) of approximately 10.0% due to the high crystallinity of these polymers. The introduction of two fluorine atoms into PNTz4T to synthesize the PNTz4T-2F polymer has boosted the PCE to 10.6%, but the introduction of four fluorine atoms to synthesize the PNTz4T-4F polymer negatively affects the efficiency (PCE ? 6.5%), implying that the number of fluorine atoms is not yet optimized. We have developed a new synthetic route for a novel monofluoro-bithiophene monomer and successfully synthesized a novel PNTz4T-1F polymer. The fullerene-based PSCs based on our novel PNTz4T-1F polymer processed using a halogen-free solvent system demonstrated an outstanding PCE of 11.77% (11.67% certified), representing the highest PCE reported thus far in the literature. Due to the optimum molecular ordering/packing, improved interaction with PC71BM and interconnectivity between photoactive material domains, PNTz4T-1F-based PSCs exhibit lower charge carrier recombination and enhanced charge carrier mobility levels, leading to a substantially high photocurrent density (20.37 mA cm(cid:2)2). These results create new means to tune the structural properties of polymers, ultimately leading to the realization of this class of solar cells for practical applications.
关键词： polymer solar cells,nanoscale morphology,halogen-free solvent,power conversion efficiency,fluorination
更新于2025-09-16 10:30:52
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Significantly improving the performance of polymer solar cells by the isomeric ending-group based small molecular acceptors: Insight into the isomerization
摘要： Compared to benzene-fused end-capping groups (EGs), thiophene-fused EGs have some unique characteristics due to the non-centrosymmetric structure of the thiophene ring, which make them easy to form different types of isomers. Here, we develop three isomeric brominated thiophene-fused EGs, which are linked to the IDTT core to acquire three novel isomeric small-molecule acceptors (SMAs) named ITC-2Br, ITC-2Br1, and ITC-2Br2. From ITC-2Br to ITC-2Br1, the change of the bromine substituent group on the thiophene ring has only a minor impact on the physicochemical properties and photovoltaic performance. However, from ITC-2Br to ITC-2Br2, the change in the fused sites on the thiophene leads to dramatically modified absorption, energy levels, and photovoltaic performance. Theoretical simulations provide an in-depth understanding of the absorption and electrochemical differences among the three acceptors. Thanks to the favorable properties, the ITC-2Br2-based polymer solar cells (PSCs) yield a significantly higher power conversion efficiency (PCE) (13.1%) than the devices based on ITC-2Br (10.9%) and ITC-2Br1 (11.9%). From the ITC-2Br-, ITC-2Br1- to the ITC-2Br2-based devices, the JSC and FF exhibit a monotonic increase similar to the trend of PCE, which demonstrates the success of the isomerization strategy, highlighting its future prospects for the development of high-performance SMAs.
关键词： polymer solar cells,power conversion efficiency,isomerization,small-molecule acceptors,end-capping groups
更新于2025-09-16 10:30:52