Improving Voc of CdSe/CdTe Solar Cells via Incorporating Oxygenated CdS Between Front Buffer and Absorber

The recent trend in enhancing the performance of cadmium telluride (CdTe) solar cells involves alloying CdTe with selenium (Se) and substituting the window layer, cadmium sulfide (CdS), with magnesium zinc oxide (MZO). However, the stability and reproducibility of MZO raise concerns. Recent studies have proposed the use of commercial SnO
2
in place of MZO and introducing oxygenated CdS between SnO
2
and the absorber, achieving an efficiency of over 20℅. This significant Voc gain is ascribed to the photoactive bandgap gradient region, Cd(O,S,Se,Te), formed at the device's front interface, which avoids a detrimental interface. To assess the general applicability of this finding, we analyzed CdSe/CdTe devices' performance using MZO and indium gallium oxide (IGO) compared to SnO
2
. We discovered that incorporating the oxygenated CdS layer notably improved the V
oc
of devices across all three buffers, achieving 876 mV, which closely aligns with the previously simulated value of 882 mV for SnO
2
. Steady-state and time-resolved photoluminescence measurements indicate that the Voc improvement results from significantly reduced carrier recombination at the front of the device.