Mapping carrier lifetime variations in polycrystalline CdTe thin films using confocal microscopy

We discuss the optoelectronic property variation between grains and grain boundaries of CdTe polycrystalline thin films using a confocal microscopy system. Single-photon photoluminescence (PL) and time-resolved photoluminescence spectroscopy (PL) is used to map a 10 × 10 μm
²
area at the back surface of CdTe with an optical resolution of 10
⁴
nm. TRPL maps show that different grain boundaries have different near-surface lifetimes. Surprisingly, grain-boundaries with high near-surface lifetime are associated with regions of the sample that have low PL yield. This study demonstrates the potential of confocal PL and TRPL mapping to understand carrier lifetime variations in thin films.