23% enhanced efficiency of polymer solar cells processed with 1-chloronaphthalene as the solvent additive

Power conversion efficiency (PCE) of polymer solar cells fabricated with {4,8-bis(4,5-didecyl-2-thienyl)-benzo[1,2-b:4,5-b′]dithiophene-alt-[4,9-bis(4-hexyl-2-thienyl)-naphtho[1,2-c:5,6-c′]bis[1,2,5]thiadiazole-5,5-diyl]} (PBDT-DTNT) as the electron donor and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) as the electron acceptor was improved from 5.33% to 6.57% by adding 1% of 1-chloronaphthalene as the solvent additive into o-dichlorobenzene which was used as the solvent for both PBDT-DTNT and PC71BM. The enhanced PCE was attributed to optimized surface morphology and packed polymer chains leading to better phase separation morphology by the solvent additive.