Simple alcohol solvent treatment enables efficient non-fullerene organic solar cells

We systematically investigated the impacts of alcohol solvent treatments on the performance of non-fullerene organic solar cells (OSCs) with poly[(2,6-(4,8-bis(5-(2-ethylhexypthiophen- 2-yl)benzo[1,2-b:4,5-b0]dithiophene)-co-(1,3-di(5-thiophene-2-yl)-5,7-bis(2-ethylhexyl) benzo[1,2-c:4,5-c0]di thiophene-4,8-dione)] (PBDB -T): 3,9-bis(2-methylene-(3 -(1,1- dicyanome thylene)-indanone))-5,5,11,11- tetrakis(4-hexylphenyl)-dithieno[2,3-d:20,30-d']-sindaceno[1,2-b:5,6-b0]dithiophene(ITIC) as active layers. The result demonstrates that various alcohol solvents, including methanol, ethanol, n-propanol and n-butanol can bring on the improvement of device performance. Notably, when ethanol with a moderate boiling point is adopted, the power conversion efficiency can be significantly boosted to 10.53% from 8.31% (as-cast device). The performance enhancement is mainly attributed to the optimized vertical phase separation and increased charge carrier mobility of the active layer, leading to efficient charge separation and balanced charge transportation, respectively. This work indicates that alcohol solvent treatment is a facile and effective approach to improve the performance of non-fullerene OSCs.