Study of Burn-In Loss in Green Solvent-Processed Ternary Blended Organic Photovoltaics Derived from UV-Crosslinkable Semiconducting Polymers and Nonfullerene Acceptors

Abstract

This work deals with the investigation of burn-in loss in ternary blended organic photovoltaics (OPVs) prepared from a UV-crosslinkable semiconducting polymer (P2FBTT-Br) and a nonfullerene acceptor (IEICO-4F) via a green solvent process. The synthesized P2FBTT-Br can be crosslinked by UV irradiation for 150 s and dissolved in 2-methylanisole due to its asymmetric structure. In OPV performance and burn-in loss tests performed at 75 degrees C or AM 1.5G Sun illumination for 90 h, UV-crosslinked devices with PC71BM show 9.2% power conversion efficiency (PCE) and better stability against burn-in loss than pristine devices. The frozen morphology resulting from the crosslinking prevents lateral crystallization and aggregation related to morphological degradation. When IEICO-4F is introduced in place of a fullerene-based acceptor, the burn-in loss due to thermal aging and light soaking is dramatically suppressed because of the frozen morphology and high miscibility of the nonfullerene acceptor (18.7% -> 90.8% after 90 h at 75 degrees C and 37.9% -> 77.5% after 90 h at AM 1.5G). The resulting crosslinked device shows 9.4% PCE (9.8% in chlorobenzene), which is the highest value reported to date for crosslinked active materials, in the first green processing approach.