Recombination mechanisms in CIGS solar cells: Insights from temperature-dependent electrical measurements

Temperature, a key environmental factor affecting photovoltaic devices, strongly influences the electrical performance of CIGS solar cells. This study examines cells with 30 and 60 nm CdS buffer layers using temperature-dependent current–voltage and capacitance–voltage (C–V) measurements. While both structures show similar efficiency temperature coefficients, the underlying recombination mechanisms differ: thin-buffer cells are dominated by interface-related processes, whereas standard-buffer cells exhibit more bulk-controlled behavior. C–V profiling indicates that thermally activated changes in carrier concentration shift with buffer thickness, occurring near the heterojunction in thin-buffer cells and deeper in the absorber for thicker layers. These spatial differences are consistent with thermally activated (VSe−VCu) defect transformations. Overall, temperature-dependent electrical characterization provides insight into dominant recombination pathways and reveals how buffer thickness influences the location and impact of thermally activated defect states in CIGS heterostructures.