Lateral charge carrier transport in Cu(In,Ga)Se2 studied by time-resolved photoluminescence mapping

Abstract

Electronic transport in a semiconductor is key for the development of more efficient devices. In particular, the electronic transport parameters carrier lifetime and mobility are of paramount importance for the modeling, characterization, and development of new designs for solar cells and optoelectronic devices. Herein, time-resolved photoluminescence mapping under low injection and wide-field illumination conditions is used to measure the carrier lifetime and analyze the lateral charge carrier transport in Cu(In,Ga)Se2 absorbers grown at different temperatures, on different substrates, and subject to different postdeposition treatments (PDT) with light or heavy alkalis. To estimate the carrier mobility, numerical simulations of carrier diffusion transport to areas of increased recombination (defects) are used, similarly as observed experimentally. Mobilities are found in the range of 10–50 cm2 V−1 s−1, and effective minority carrier lifetime between 100 and 800 ns resulting in carrier diffusion lengths of 2–9 μm depending on the sample. Finally, the factors limiting carrier mobility and the implications of carrier diffusion on the measured carrier lifetimes are discussed.