Transient Photocurrents In Polymer Solar Cells Based On P3HT:PCBM

This thesis focuses on polymer bulk-heterojunction solar cells based on poly(3-hexylthiophene) and [6,6]-phenyl C60-butyric acid methyl ester (P3HT:PC6oBM). We study the transport of charge carriers in the photovoltaic devices by transient photocurrent measurement. Transient photocurrent curves help explain the mechanism of trap effect and carrier recombination. The main results are as follows:(?) By illuminating the devices with square pulses of light of varying intensity or width which are set by a transient photocurrent system, we investigated the transient photocurrent curves on the microsecond to millisecond timescale which were affected by intensity, pulse width and wavelength of the incident light. A slow rise and an exponential decrease in curves show the relation between trap effect and recombination of carriers.(?) With an additional constant background illumination, all of the transient photocurrent curves for different pulse intensities have the same shape, consistent with the features resulting from a dynamic processes related to the equilibrium of trapping and detrapping rates.