Revealing the role of valence band DOS in modulating band bending for efficient solar energy harvesting

Accurately measuring the density of states in solar cell devices poses significant experimental challenges. Hence, a comprehensive simulation-based analysis becomes essential to unravel its impact with precision. This study presents a computational approach to enhance crystalline silicon (c-Si) solar cell performance by engineering the valence band density of states. The control of the density of states is shown to produce additional effective electric field in device that thermodynamically accelerates charges towards layers with high density of states, thereby facilitating minimization of both electrostatic and statistical potential. Hence, at the minimum valence band density of states in the absorber layer i.e., at ~ 10 17 cm − 3 , (i) spatial gradient in conduction and valence band, built-in potential, carrier density, lifetime and mobility are increased, and (ii) radiative, Auger, SRH recombination rate, recombination current and charge capture rate are decreased. Consequently, the V OC , J SC , FF and PCE becomes effectively independent of high defect density values in the range 10 9 -10 12 cm − 3 . As a result, the device achieves over 30% efficiency using 100 μm thick c-Si layer, and external quantum efficiency exceeding 80%.