Optoelectronic Properties of a Fullerene Derivative Containing Adamantane Group

A fullerene derivative linked with an adamantane cage, [6,6]-phenyl-C₆₁-butyric acid 1-adamantane methyl ester (PC₆₁BAd), has been designed and synthesized. Systematic investigations on its organic field effect performance, photovoltaic properties, and corresponding thermal stability have been made. In OFET device, the electron mobility (μ_e) of PC₆₁BAd was found to reach a value as high as 0.01 cm²/V·s with a high on-off (I_on/I_off) ratio of 4.9 × 10⁶ that is useful for logic device applications. In the organic photovoltaic devices of P3HT:PC₆₁BAd, the power conversion efficiency (PCE) was found to reach 3.31 % in the optimized device. More importantly, the active layer of P3HT:PC₆₁BAd was found to exhibit superior thermal stability over that of P3HT:PC₆₁BM. After heating at 150 °C for 20 h, the P3HT:PC₆₁BAd device still showed a PCE of 2.44 %, demonstrating the applicability of PC₆₁BAd as an acceptor material for the preparation of thermally stable organic solar cells. X-ray diffraction and atomic force microscopy were employed to probe the structure and morphology of PC₆₁BAd and to rationalize its performance as an organic electronic material.