RETRACTED ARTICLE: The highest power conversion efficiencies in poly(3-hexylthiophene)/fullerene photovoltaic cells modified by rod-coil block copolymers under different annealing conditions

Abstract

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 hydrophilic 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 (J sc ). Although PCEs were higher in untreated hydrophobic-compatibilized devices (e.g., 4.07 vs. 1.52%), the hydrophilic-compatibilized systems further benefited from thermal and solvent annealings (e.g., 4.78 vs. 3.71%). The J sc 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%).