Exploiting Ternary Blends to Accurately Control the Coloration of Semitransparent, Non‐Fullerene, Organic Solar Cells

Abstract

Semitransparent organic solar cells (STOSCs) have received increasing attention due to promising applications such as building‐integrated photovoltaics. Successful commercialization requires that STOSCs are aesthetically pleasing as well as having balanced power conversion efficiencies (PCEs) and average visible transmittances (AVTs). Non‐fullerene acceptors, which possess excellent electrical/chemical properties, have helped STOSCs to achieve high PCE and AVT; however, research related to modulating color and appearance of STOSCs has lagged behind. Herein, narrow bandgap donor and acceptor (PTB7‐Th and IEICO‐4F) and ultra‐wide bandgap acceptors (T2‐ORH and T2‐OEHRH) are used to achieve semitransparency and controllable device coloration. Blend films with controllable colors including cyan → blue → purple → reddish purple colors are successfully demonstrated, which are controlled by ratios of IEICO‐4F:T2‐ORH or IEICO‐4F:T2‐OEHRH with PTB7‐Th. By incorporating semitransparent electrodes (comprising Sb2O3/Ag/Sb2O3), STOSCs with PCEs of 6–7% are achieved for cyan, aqua, indigo, and purple and ≈4% PCEs for reddish‐purple colors, with AVTs in the range of 23–35%. Moreover, optical properties of blend films are studied via absorption and transmission measurements, whereas the range of colors achieved is quantified using commission internationale de l'éclairage (CIE) chromaticity and CIE L * a * b* color space then represented as RGB color models.