Rational Design of 2D p–π Conjugated Polysquaraines for Both Fullerene and Nonfullerene Polymer Solar Cells

Abstract

So far, squaraine‐based polymer donors have been less explored for the bulk heterojunction (BHJ) polymer solar cells. In this work, two new p–π conjugated polysquaraines (PASQ‐BDT1 and PASQ‐BDT2) with different electron‐rich subunits on the squaraine skeleton are rationally developed as new polymer donors based on the 2D structure design concept. PASQ‐BDT2 with N,N‐diisobutylaniline subunits shows superior device performances in both fullerene and nonfullerene PSCs compared to PASQ‐BDT1 containing triphenylamine subunits, with power conversion efficiencies (PCEs) of 4.34% and 3.72%, respectively, owing to increased light‐harvesting ability and more favorable nanoscale morphology in the BHJ films. Moreover, its demonstrated that solvent effects can play an effective role in elevating the device performance. For the PASQ‐BDT2/PC71BM blend, the PCE is improved from 3.19% to 4.34% after solvent vapor annealing treatment, mainly attributed to the optimized film morphology and increased hole mobility. More interestingly, when the processing solvent for nonfullerene devices is changed from chlorobenzene to chloroform, a significant enhancement on PCE from 1.96% to 3.72% is yielded for the PASQ‐BDT2/ITIC blend, due to suppressed charge recombination and enhanced crystallinity in the chloroform‐processed BHJ films.

Advances in Polymethine Dyes for Near‐Infrared Organic Photodiodes†

“…[ 81‐82 ] In addition, SQs also show a compatibility with non‐fullerene acceptors (NFAs). [ 83 ] In 2020, a BHJ OPD based on SQ:NFA blend film was successfully fabricated by Pecunia et al ., showing an appreciable D * of 4.70 × 10 11 Jones at 740 nm. [ 84 ] These results suggest that SQs may show greater potential for the development of high‐ performance NIR OPDs.…”

Squaraine Dyes for Photovoltaic and Biomedical Applications

“…We then further developed two wide bandgap polysquaraines, i.e., SQ61 and SQ62, with suitable energy levels by using BDT as the copolymerization unit. [ 79 ] In both fullerene and nonfullerene OSCs, SQ62 showed superior device performance than that of SQ61 due to more favorable nanoscale morphology and enhanced hole mobility in the BHJ films. Moreover, it is demonstrated that solvent vapor annealing (SVA) played an effective role in improving the device performance by optimizing the BHJ morphology and increasing the hole mobility.…”