Electron and hole mobility in solution-processed small molecule-fullerene blend: Dependence on the fullerene content

Abstract

We present a study of electron and hole mobility in blends of the solution-processed small molecule (DTS(PTTh2)2):fullerene as a function of the fullerene content. The mobilities are measured using the Field–Effect Transistor device configuration with the blend as the material in the channel. The hole mobility of the small molecule increases when about 10% of [6-6]-phenyl C71 butyric acid methyl ester (PC70BM) is added and then decreases at higher fullerene content. The electron mobility always increases as the fullerene content increases. Balanced charge transport occurred at 70:30 and 60:40 donor to acceptor ratios in the DTS(PTTh2)2:PC70BM system. The observation of balanced charge mobility agrees well with the reported solar cell performance.