Time-resolved photocurrent and photoluminescence spectra of GaInP/GaAs single-junction photovoltaic devices

Abstract

A pulse-laser based time-resolved photocurrent (TRPC) and photoluminescence (TRPL) system with a programmable Boxcar integrator/averager system incorporated was implemented to investigate the optical properties and charge carrier dynamics in a GaInP/GaAs single-junction photovoltaic device for the purposes of understanding fundamental optoelectronic processes in the solar cell. The implementation of whole system was realized by integrating the instrument of a Boxcar averager system with a pulse laser source + spectroscopic facilities. The delay time control and data acquisition were organized by the software code. The effects of the hardware configurations and the software parameters on the performance of the system were particularly addressed for the optimization of measurement conditions and precisions. Two main functions of TRPC and TRPL with a wide time range were demonstrated for the system. The system was employed to measure temperature- and bias voltages-dependent TRPC and TRPL spectra of a GaInP/GaAs single-junction photovoltaic device. The spectral data show a lot of information about the transient dynamic behaviors of photogenerated charge carriers in the device, including both the rise and decay processes. Interestingly, the measured time-resolved photocurrent curves are characterized by a fast rising edge followed by a relatively slow decay process as the temperature increases. Relevant theoretical calculations and analysis to the experimental curves were also carried out to understand diffusion and transport processes of charge carriers inside the device. The results show that the variation in temperature and reverse biases results in the structural change in the space charge region of the P-N junction and therefore affects the rise and decay time constants of the time-resolved photocurrent. The TRPL spectral data give information of mid-way radiative recombination of charge carriers in the device.