Unfused Nonfullerene Acceptors Based on Simple Dipolar Merocyanines

Abstract

Merocyanine (MC) dyes exhibit facile synthesis and attractive optical properties, making them widely studied as the donor materials in organic solar cells (OSCs). In this study, for the first time, simple indole‐based MCs are successfully designed as unfused nonfullerene acceptors (NFAs) for OSCs by forming dimers with A−D‐π‐D−A structure, which possess enhanced photostability compared to the well‐known ITIC acceptor and high electron mobility in blend films. When blended with P3HT donor, one of the dimers, i. e. Z2, shows a good cell efficiency of 3.53 %, which outperforms the performance of most of P3HT/NFA blends, particularly for unfused systems, and thus indicates good potential of simple MCs as NFAs.

Design of a Fully Non‐Fused Bulk Heterojunction toward Efficient and Low‐Cost Organic Photovoltaics

“…The situation is more complicated when the BHJ layers are composed of donor and acceptor materials both possessing non‐fused chemical structures. The current challenge for non‐fused BHJ OPV cells is the relatively low efficiency of about 4 %, [7] which requires new molecular design strategies to address the molecular packing and BHJ morphological modulation. Generally, alkyl‐, alkoxyl‐, and alkylthio side chains have been widely used to adjust the solubility of the photoactive materials, modulate the molecular orientations and carrier transports, and optimize the D : A morphology.…”

“…However, the morphological properties are even harder to be modulated, implicitly, in the BHJ blend films containing donor and acceptor materials which are both with non‐fused ring chemical structures. According to the previous work, almost no work has reported FFs over 0.7 in the non‐fused BHJ‐based OPV cells [7] . On the one hand, the molecules with higher freedom of rotation are more likely to twist during the BHJ films formation or post‐treatment processes (thermal annealing or solvent annealing etc.…”

“…According to the previous work, almost no work has reported FFs over 0.7 in the non-fused BHJbased OPV cells. [7] On the one hand, the molecules with higher freedom of rotation are more likely to twist during the BHJ films formation or post-treatment processes (thermal annealing or solvent annealing etc. ), resulting in the variation of aggregation behaviors of the blend films.…”