Realization of Performance Enhancement in Ternary Polymer Solar Cells by Broad Absorption, Efficient Energy Transfer, and Balanced Charge Carrier Mobility

A smart ternary strategy was designed to improve the performance of ternary polymer solar cells (TPSCs) by doping high-mobility conjugated polymer poly{2, 2'-(2,5-bis(2-octyldodecyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3, 4-c]pyrrole-1, 4-diyl)dithieno[3, 2-b]thiophene-5,5'-diyl-alt-thiophen-2,5-diyl} (PDPPBTT) into the dominating poly({4,8-bis[(2-ethylhexyl)oxy] benzo[1,2-b:4,5-b'] dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethy-lhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7):[6,6]-phenyl C71 -butyric acid methyl ester (PC71BM) system. The enhanced short-circuit current and stable fill factor were simultaneously obtained. The champion power conversion efficiency of TPSCs with only 0.5 wt% PDPPBTT arrived to 7.89% with 21.6% improvement compared with the binary device, which was mainly attributed to good absorption in the infrared region, appropriate energy cascade alignment, efficient Förster resonance energy transfer from PTB7 to PDPPBTT, and more balanced hole-electron mobility. Moreover, as a third component, PDPPBTT enhanced the crystallinity and optimized the morphology of ternary blends. It was also found that the incorporation of PDPPBTT increased the charge carrier lifetime, ensuring efficient charge carrier transport and collection with suppressed bimolecular recombination.