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Reduced Non-radiative Recombination Energy Loss Enabled Efficient Polymer Solar Cells via Tuning Alkyl Chain Positions on Pendent Benzene Units of Polymers
摘要： Non-radiative recombination energy loss (ΔE3) plays a key role in enhancing device efficiencies for polymer solar cells (PSCs). Up to now, there is no clear resolution for reducing ΔE3 via molecular design. Herein, we report two conjugated polymers, PBDB-P-p and PBDB-P-m, which are integrated from benzo[1,2-b:4,5-b′]dithiophene (BDT) with alkylthio chain substituted at para- or meta- position on pendent benzene and benzo[1,2-c:4,5-c′]dithiophene-4,8-dione (BDD). Two polymers have different temperature-dependent aggregation properties, but similar molecular energy levels. When BO-4Cl was used as acceptor to fabricate PSCs, the device of PBDB-P-p:BO-4Cl displayed a maximal power conversion efficiency (PCE) of 13.83%, while the best device of PBDB-P-m:BO-4Cl exhibited a higher PCE of 14.12%. The close JSCs and FFs in both PSCs are attributed to their formation of effective nanoscale phase-separation as confirmed by atomic force microscopy (AFM) measurements. We find that the PBDB-P-m-based device has one order of magnitude higher of electroluminescence quantum efficiency (EQEEL) than that in PBDB-P-p-based one, which could arise from the relatively weak aggregation in PBDB-P-m-based film. Thus, the PBDB-P-m-based device has a remarkably enhanced VOC of 0.86 V in contrast to 0.80 V in PBDB-P-p-based device. This study offers a feasible structural optimization way on the alkylthio side chain substitute position on the conjugated polymer to enhance VOC by reducing non-radiative recombination energy loss in resulting PSCs.
关键词： polymer solar cells,open-circuit voltage,non-radiative recombination energy loss,polymer donor,alkylthio substituted position
更新于2025-09-23 15:21:01
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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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Understanding the Impact of Side-chain on Photovoltaic Performance in Efficient All-polymer Solar Cells
摘要： In order to understand the impact of side-chain on photovoltaic performance and explore efficient All-polymer solar cells, chemical modifications on donor-acceptor based polymers containing benzo[1,2-b:4,5-b’]dithiophene (BDT) and thieno[3,4-c]pyrrole-4,6-dione (TPD) backbones were performed. Via side-chain fluorination, the molecular design resulted in lower highest occupied molecular orbital (HOMO) energy levels and enhanced backbone planarity. The intermolecular packing and solid-state ordering were found to significantly improve. These factors are considered as key influences for carrier transport. In contrast, introducing a bulky alkylthio substituent group was found to slightly distort the polymer backbone. As a result of the lower HOMO level, PTF8 exhibits an improved open circuit voltage (Voc) compared to the template polymer PT8. However, due to the increased crystallinity and aggregation, PTF8 and PTS8 experience an unfavorable phase separation in polymer-polymer bulk heterojunction blends, hindering the PCE to about 4%. Through introducing alkylthio side-chains and fluorination, the polymer PTFS8 exhibits an extremely low HOMO level (-5.73 eV). These reduced HOMO level limits charge separation between the donor and acceptor polymers. Without any fluorination and alkylthio side-chains, the wide bandgap polymer PT8 exhibits desired HOMO energy levels and crystallinity, delivering a best PCE of 8% together with a high Voc of 1.05 V, displaying its great potential for applications in efficient all-polymer optoelectronic devices.
关键词： BDT-TPD backbone,side-chain,fluorination,All-polymer solar cells,alkylthio substitution,photovoltaic performance
更新于2025-09-12 10:27:22
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Comparative study on the effects of alkylsilyl and alkylthio side chains on the performance of fullerene and non-fullerene polymer solar cells
摘要： Two novel high gap donor polymers – PBDTTSi-TzBI and PBDTTS-TzBI, based on imide fused benzotriazole (TzBI) with asymmetric side chains and alkylsilyl (Si) or alkylthio (S) substituted 4,8-di(thien-2-yl)benzo[1,2-b:4,5-b′]dithiophene (BDTT) – are successfully synthesized. The effect of the side chain variation on the photophysical, morphological and photovoltaic properties of blends of these polymers with fullerene and non-fullerene acceptors is investigated. The PBDTTSi-TzBI polymer shows a deeper highest occupied molecular orbital energy level, which results in higher open-circuit voltages. Nevertheless, the polymer solar cells fabricated using PBDTTS-TzBI in combination with PC71BM afford a higher power conversion efficiency of 7.3% (vs 4.0% for PBDTTSi-TzBI:PC71BM). By using the non-fullerene acceptor ITIC, the absorption of the blends extends to 850 nm and better device efficiencies are achieved, 6.9% and 9.6% for PBDTTSi-TzBI:ITIC and BDTTS-TzBI:ITIC, respectively. The better performance for PBDTTS-TzBI:ITIC is attributed to the strong and broad absorption and balanced charge transport, and is among the best so far for non-fullerene solar cells based on TzBI-containing polymer donors.
关键词： Alkylthio,Benzotriazole,Alkylsilyl,Polymer solar cells,Non-fullerene acceptors,Photovoltaic properties
更新于2025-09-11 14:15:04