Near-infrared non-fused ring acceptors with light absorption up to 1000 nm for efficient and low-energy loss organic solar cells

Abstract

It is challenging to afford both high-performance and low-energy loss (Eloss) organic solar cells (OSCs) based on near-infrared (NIR) non-fused ring electron acceptors (NFREAs) with ultra-narrow bandgap. Herein, three simple NFREAs (C6OT-4F, C6EDOT-4F and PDOT-4F) with absorption up to 1000 nm are developed by using alkoxy substituted thiophene derivatives core connected to fluorinated 1,1-dicyanomethylene-3-indanone (DFIC) terminals through 4H-cyclopenta[1,2-b:5,4-b’]dithiophene (CPDT) bridge. It is found that fine tuning central thiophene derivatives can surprisingly lead to different photoelectric properties and the device performances. Compared with C6EDOT-4F and PDOT-4F, C6OT-4F shows a blue-shifted absorption and an elevated LUMO level, which is beneficial for boosting Voc. As a result, optimal devices based on PTB7-Th:C6OT-4F achieve a preferable efficiency of 9.83% with a low Eloss of 0.47 eV, which is the lowest Eloss among the NFREA-based OSCs with PCE >9% and optoelectronic response over 1000 nm. This work portrays the design concept of ultra-narrow bandgap NFREAs for efficient OSCs as well as low energy loss and exploration of semitransparent photoelectric devices.