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.
Highlights
Electronic transport in a semiconductor is key for the development of more face recombination cases, in which a high efficient devices
To study the lateral diffusion of charge carriers, we focus on the temporal variation of the PL signal near extended defects found in CIGS absorbers of different material quality
One clear defect is observed for NaF þ RbF on soda-lime glass (SLG), which expands over time
Summary
To study the lateral diffusion of charge carriers, we focus on the temporal variation of the PL signal near extended defects found in CIGS absorbers of different material quality. A defective region with intricate shape is discernible at early times The interaction of these distinguishable defects is evident by comparing the initial and end time, for which the extended influence of each defect merges to form a single dark region. Whereas the individual contribution of different defects are resolved at the initial time, at the end time (or using time-integrated data) the defects appear merged This is a consequence of carrier diffusion from defective-free areas to the defect under wide-field illumination, exemplifying the loss of optical resolution of the technique, as previously shown,[32] consistently with other studies found in the literature for GaAs and epitaxial CdTe.[19,31,33]
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