The study of influence of doping by iodine or gallium on the lifetime of photogenerated current carriers in CdTe

This study investigated how doping by iodine or gallium affects processes associated with current carriers by undertaking a kinetics investigation of electron loss processes in the CdTe samples prepared by direct ampoule method. Owing to these processes, the current carriers generated by light can be trapped or recombined after a thermalization process and fail to reach electrodes during their lifetime and adversely impact the photovoltaic performance of solar cells. The microwave photoconductivity method provides an effective means of obtaining direct data on the lifetime and energy distribution of traps for current carriers. The obtained lifetimes in doped materials were compared to those in initial polycrystalline CdTe and monocrystalline CdTe. The experimental results indicate that the free electron lifetimes become higher after the doping. We found that the lifetime in the doped polycrystalline samples was equal (for I-doped samples) or even higher (for Ga-doped samples) than in CdTe monocrystals. The model based on the self compensation effect was suggested for the explanation of the experimental results.