Co-solvent effects on the microstructure-related photovoltaic properties of organic solar cells

The current study aims to discover the key factors affecting the photovoltaic performance of poly (3-hexylthiophene) (P3HT):[6,6]-phenyl-C ₆₁-butyric acid methyl ester (PCBM) bulk heterojunction solar cells. A low-boiling-point (BP) solvent (chloroform, CF) was mixed with a high-BP solvent (1,2,4-trichlorobenzene, TCB) to dissolve the P3HT:PCBM blends. Moreover, the volume fraction of CF in the CF:TCB co-solvents was varied to fabricate blending films with different microstructures. The results indicate that the disordered P3HT chains enhanced the absorbance and improved the p-n interface of the blending films, thus enhancing the output current, voltage, and hence, the power conversion efficiency of the solar cells despite the formation of small crystalline P3HT domains that limit charge transport.