Study on the Diffusion Rate of the Charge Carrier Transport in Regio-Random and Regio-Regular P3HT

Abstract

Muon spin relaxation experiment has been conducted to probe the hopping mechanism in the poly(3-hexylthiophene-2,5-diyl) (P3HT) for both types of regio-random (Rdm) and regio-regular (RR). In this study we have performed calculations over the collected data to obtain the parallel and perpendicular diffusion rates, at temperatures of 10 K and 300 K. The calculation is based on the fitting method to the empirical function that relates the relaxation rate with the diffusion rates. For Rdm-P3HT, we have obtained the parallel diffusion rate to be 5.43 x 1013 rad/s at 300 K and 4.90 x 1014 rad/s at 10 K. While the perpendicular diffusion rates are 5.29 x 108 rad/s at 300 K and 1.88 x 106 rad/s at 10 K. For RR-P3HT, we have obtained the parallel diffusion rate to be 1.04 x 1014 rad/s at 300 K and 1.28 x 1015 rad/s at 10 K. While the perpendicular diffusion rates are 6.10 x 108 rad/s at 300 K and 5.35 x 105 at 10 K. The diffusion rates of RR-P3HT are higher than that of Rdm-P3HT, especially in the parallel direction. In both types of material, the parallel diffusion rate decreased with temperature, while the perpendicular diffusion rate increased with temperature, showing a change of behavior from 1D to 3D direction of charge transport.