Control of nanomorphology in all-polymer solar cells via assembling nanoaggregation in a mixed solution

The formation of interconnected phase-separated domains on sub-20 nm length scale is a key requirement for all-polymer solar cells (all-PSCs) with high efficiency. Herein, we report the application of crystalline poly(3-hexylthiophene) (P3HT) nanowires via an O-dichlorobenzene/hexane mixed solution blended with poly{(9,9-dioctylfluorenyl-2,7-diyl)-alt-[4,7-bis(3- hexylthiophen-5-yl)-2,1,3-benzothiadiazole]-2′,2″-diyl} (F8TBT) for the first time. The nanomorphology of P3HT:F8TBT all-PSCs can be controlled by P3HT nanowires. The improved film morphology leads to enhanced light absorption, exciton dissociation, and charge transport in all-PSCs, as confirmed by ultraviolet-visible absorption spectra, X-ray diffraction, transmission electron microscopy, atomic force microscopy, and time-resolved photoluminescence spectra. The P3HT nanowire:F8TBT all-PSCs could achieve a power conversion efficiency of 1.87% and a V_oc of 1.35 V, both of which are the highest values for P3HT:F8TBT all-PSCs. This work demonstrates that the semiconductor nanowires fabricated by the mixed solvents method is an efficient solution process approach to controlling the nanomorphology of all-PSCs.