This study evaluates the burn-in loss phenomenon in ternary blended OPVs prepared from UV crosslinkable semiconducting polymers and a nonfullerene acceptor via an environmentally benign process. In OPV performance and burn-in loss tests carried out under thermal aging and light soaking conditions (75 °C and AM 1.5G sun illumination for 90 h), UV-crosslinked devices with fullerene-based acceptors show 9.2% of PCE and better stability against burn-in loss than pristine devices. The frozen morphology derived from crosslinking prevents lateral aggregation or crystallization related to morphological degradation. However, since the burn-in loss still exists, a nonfullerene acceptor was introduced. The resulting crosslinked device shows 9.4% of PCE (9.8 % in chlorobenzene), which is the highest value reported to date for crosslinked active materials, and dramatically reduces burn-in loss (18.7% --＞ 90.8% after 90 h at 75°C and 37.9% --＞ 77.5% after 90 h at AM 1.5G) against heat and light