High‐Yield Synthesis and Electrochemical and Photovoltaic Properties of Indene‐C70 Bisadduct

Abstract

[6, 6]‐Phenyl‐C 61‐butyric acid methyl ester (PC 60 BM) is the widely used acceptor material in polymer solar cells (PSCs). Nevertheless, the low LUMO energy level and weak absorption in visible region are its two weak points. For enhancing the solar light harvest, the soluble C 70 derivative PC 70 BM has been used as acceptor instead of PC 60 BM in high efficiency PSCs in recent years. But, the LUMO level of PC 70 BM is the same as that of PC 60 BM, which is too low for the PSCs based on the polymer donors with higher HOMO level, such as poly (3‐hexylthiophene) (P3HT). Here, a new soluble C 70 derivative, indene‐C 70 bisadduct (IC 70 BA), is synthesized with high yield of 58% by a one‐pot reaction of indene and C 70 at 180 °C for 72 h. The electrochemical properties and electronic energy levels of the fullerene derivatives are measured by cyclic voltammetry. The LUMO energy level of IC 70 BA is 0.19 eV higher than that of PC 70 BM. The PSC based on P3HT with IC 70 BA as acceptor shows a higher Voc of 0.84 V and higher power conversion efficiency (PCE) of 5.64%, while the PSC based on P3HT/PC 60 BM and P3HT/PC 70 BM displays Voc of 0.59 V and 0.58 V, and PCE of 3.55% and 3.96%, respectively, under the illumination of AM1.5G, 100 mW cm−2. The results indicate that IC 70 BA is an excellent acceptor for the P3HT‐based PSCs and could be a promising new acceptor instead of PC 70 BM for the high performance PSCs based on narrow bandgap conjugated polymer donor.