Highly Efficient and Thermally Stable Polymer Solar Cells with Dihydronaphthyl‐Based [70]Fullerene Bisadduct Derivative as the Acceptor

Abstract

Abstract The efficiency of polymer solar cells (PSCs) can be essentially enhanced by improving the performance of electron‐acceptor materials, including by increasing the lowest unoccupied molecular orbital (LUMO) level, improving the optical absorption, and tuning the material solubility. Here, a new soluble C 70 derivative, dihydronaphthyl‐based C 70 bisadduct (NC 70 BA), is synthesized and explored as acceptor in PSCs. The NC 70 BA has high LUMO energy level that is 0.2 eV higher than [6,6]‐phenyl‐C 61 ‐butyric acid methyl ester (PCBM), and displays broad light absorption in the visible region. Consequently, the PSC based on the blend of poly(3‐hexylthiophene) (P3HT) and NC 70 BA shows a high open‐circuit voltage ( V oc = 0.83 V) and a high power conversion efficiency (PCE = 5.95%), which are much better than those of the P3HT:PCBM‐based device ( V oc = 0.60 V; PCE = 3.74%). Moreover, the amorphous nature of NC 70 BA effectively suppresses the thermally driven crystallization, leading to high thermal stability of the P3HT:NC 70 BA‐based solar cell devices. It is observed that the P3HT:NC 70 BA‐based device retains 80% of its original PCE value against thermal heating at 150 °C over 20 h. The results unambiguously indicate that the NC 70 BA is a promising acceptor material for practical PSCs.