High Efficiencies in Nanoscale Poly(3-‎Hexylthiophene)/Fullerene Solar Cells

   A modified morphology was introduced for poly(3-hexylthiophene):phenyl-C71-butyric acid methyl ester (P3HT:PC71BM) bulk heterojunction (BHJ) solar cells by thermal and solvent annealing treatments in the presence of hydrophilic-hydrophobic block copolymers. Power conversion efficiency (PCE) plummet was prohibited during both thermal and solvent treatments for all BHJ devices modified with either hydrophobic- or hydrophilic-based copolymers. It was originated from ever increasing trend of fill factor (FF) and increasing or marginally decreasing trend of short circuit current density (Jsc). Although PCEs were higher in untreated hydrophobic-compatibilized devices, the hydrophilic-compatibilized systems further benefited from thermal and solvent treatments. The vertical homogeneity increased for compatibilized BHJs during annealing processes, leading to very high FFs around 70%. The maximum values of Jsc and PCE for the well-controlled photovoltaic systems were 12.10 mA/cm2 and 4.85%, respectively.