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Developing Wide Bandgap Polymers with Single Benzodithiophene-Based Unit for Efficient Polymer Solar Cells
摘要： In this work, a series of solely benzodithiophene-based wide bandgap polymer donors, namely PBDTT, PBDTS, PBDTF and PBDTCl, were developed for efficient polymer solar cells (PSCs) by just varying the heteroatoms into the conjugated side chains. The effects of sulfuration, fluorination and chlorination were also investigated systematically on the overall properties of these BDT-based polymers. The HOMO levels could be lowered gradually by introducing sulfur, fluorine and chlorine atoms into the side chains, which contributed to the stepwise increased Voc (from 0.78 V to 0.84 V) in the related PSCs using Y6 as the electron acceptor. On the other hand, above side chain engineering strategy could promote the polymer chain interactions and fine-tune the phase separation of active blends, leading to the enhanced absorption, ordered molecular packing and crystallinity. Among them, the chlorinated PBDTCl exhibited not only high level absorption and crystallinity, but also the most balanced hole/electron charge transport and the most optimized morphology, giving rise to the best PCE of 13.46% with a Voc of 0.84 V, a Jsc of 23.16 mA cm-2 and an FF of 69.2 %. The chlorination strategy afforded PBDTCl synthetic simplicity but high efficiency, showing its promising photovoltaic applications for realizing low-cost practical PSCs in near future.
关键词： synthetic simplicity,benzodithiophene,sole donor unit,wide bandgap polymer donors,polymer solar cells
更新于2025-09-23 15:21:01
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Understanding of Imine Substitution in Wide Bandgap Polymer Donor–Induced Efficiency Enhancement in All-Polymer Solar Cells
摘要： All-polymer solar cells (all-PSCs) are proven to possess outstanding thermal and mechanical stabilities. However, concurrently achieving appropriate phase-separated pattern, efficient charge transportation, and adequate charge transfer between donor and acceptor components is still a challenge, and thus, only a few polymer-polymer BHJ blends have yielded BHJ device PCEs >8%. Generally, polymer backbone substitutions may have a direct influence on the device performance. Thus, this report examines a set of wide bandgap polymer donor analogues composed of thienothiophene (TT) or thiazolothiazole (TTz) motif, and their all-PSC device performance with N2200. Results show that all-PSCs based on the imine-substituted derivative PBDT-TTz exhibit power conversion efficiencies (PCE) as high as 8.4%, which largely outperform the analogue PBDT-TT-based ones with PCEs of only 0.7%. This work reveals that the imine substitution in polymer backbones of PBDT-TTz not only increases the ionization potential (IP) and electron affinity (EA), narrows the optical gap (Eopt), but also has significantly impacts on the BHJ film morphologies. PBDT-TTz:N2200 BHJ blends present better miscibility, suppressed phase separation, much stronger crystallinity, and face-on ordering, which are contributed to efficient exciton dissociation, charge transportation, and therefore, high-efficiency in all-PSCs. This study demonstrates that the imine-substituted polymers composed of TTz motif, which can be easily synthesized through a facile two-step procedure, are a promising class of wide bandgap polymer donors for efficient all-PSCs.
关键词： Imine substitution,All-polymer solar cells,Thiazolothiazole,Wide bandgap polymer donors,BHJ film morphologies
更新于2025-09-12 10:27:22