Efficient ternary organic photovoltaic using polymers donor with two absorption peaks and similar HOMO levels as third component materials

Abstract

The ternary strategy has been shown to be a promising approach to improve the performance of organic solar cells (OSCs). In this manuscript, the polymer donor Poly[N-9″-hepta-decanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole) (PCDTBT) was doped into a D18-Cl:Y6 binary film to fabricate ternary OSCs. PCDTBT has efficient short wavelength light absorption, appropriate content of PCDTBT yielded complementary absorption spectra, and good compatibility with the D18-Cl:Y6 binary films. In addition, the lower lowest unoccupied molecular orbital levels of PCDTBT than D18-Cl allow efficient exciton dissociation and reduce charge carrier recombination within the ternary film. The optimized ternary film has a more suitable phase separation scale, smooth surface, and higher crystallinity than D18-Cl:Y6 binary films. Therefore, the appropriate content of PCDTBT as the third component material can significantly enhance the short-circuit current density (JSC) and photovoltaic performance. The results show that ternary OSCs with both D18-Cl and PCDTBT donors can achieve high performance by well-optimized light absorption, exciton dissociation, and phase separation.