Samira Agbolaghi - Institute of Polymeric Materials, Sahand University of Technology, Tabriz, Iran
Saleheh Abbaspoor - Institute of Polymeric Materials, Sahand University of Technology, Tabriz, Iran
Javad Najjari - Institute of Polymeric Materials, Sahand University of Technology, Tabriz, Iran
Mojgan Mahmoudi - Institute of Polymeric Materials, Sahand University of Technology, Tabriz, Iran

A best-performing morphology was proposed for poly(3-hexylthiophene):phenyl-C71-butyric acid methyl ester (P3HT:PC71BM) bulk heterojunction (BHJ) solar cells by thermal and solvent annealings in the presence of rod-coil block copolymers subsuming ydrophilic and hydrophobic coily blocks. Unlike uncompatibilized photovoltaic cells, the power conversion efficiency (PCE) dropping during both thermal and solvent annealings was prevented for all BHJ devices compatibilized with either hydrophobic- or hydrophilic-based copolymers. The observed behavior was assigned to ever increasing trend of the fill factor (FF) and increasing or marginally decreasing trend of short circuit current density (Jsc). Although PCEs werehigher in untreated hydrophobic-compatibilized devices (e.g., 4.07% versus 1.52%), the hydrophiliccompatibilized systems further benefited from thermal and solvent annealings (e.g., 4.78% versus 3.71%). The Jsc and PCE peaked at 12.10 mA/cm2 and 4.85%, respectively, within 1 h under solvent annealing by 20 wt% of P3HT7150-b-polystyrene compatibilizer. Based on dynamic secondary ion mass spectrometry(DSIMS) analyses, the vertical homogeneity increased for compatibilized BHJs during both thermal and solvent annealings, leading to very high FFs (~69%).

P3HT, PC71BM, bulk heterojunction, PCE, solar cell