Direct observation of slow transient response of photovoltage for carrier dynamics in Cu(In,Ga)Se2 via surface photovoltage measurement

A direct investigation of the carrier generation and slow transient mechanism related to the photovoltage characteristics of Cu(In,Ga)Se2 (CIGS) was conducted using the transient surface photovoltage (t-SPV) measurement. The focus was placed on the slow transient response of the photovoltage, which reflects carrier transport processes, such as trapping/detrapping, occurring during device operation. The applicability of t-SPV to directly probe the carrier dynamics related to photovoltage characteristics was investigated for CIGS thin films, CdS/CIGS pn junctions, and CIGS solar cells. The results provided valuable insights into the slow transient response of the photovoltage for evaluating the device performance. In addition, the excitation intensity-dependent SPV measurements supported the t-SPV findings. Overall, t-SPV is a promising and straightforward method that may serve as a practical tool for direct performance evaluation of various optoelectronic devices.