Comparative analysis of solar cell architecture utilizing thermionic emission based carrier transport versus tunneling transport

Abstract This work explored designing a solar cell to utilize sub-bandgap photons along with conventional above-bandgap photons using a periodic stack of MASnI3 and MASnBr3 perovskite layers. Based on the stacking pattern, two distinct configurations emerge. First, an ultrathin wide bandgap MASnBr3 layer is embedded in a narrow bandgap MASnI3 absorber, creating a potential hill that favours tunneling transport. In the second configuration, an ultrathin narrow bandgap MASnI3 layer is embedded in wide bandgap MASnBr3 absorber, making a potential well that supports thermionic emission dominated transport. The proposed superlattice design functions similarly to multi-energy level, enhancing the utilization of the incident spectrum by capturing sub-bandgap photons and reducing thermalization. We evaluated these tunneling and thermionic emission dominated device configurations across various operational aspect including carrier transport, recombination, and enhancement in incident spectrum utilisation. The physical parameters controlling device performance such as barrier height, thickness are optimized. The optimal efficiency observed was 35.7%, higher than the Schokley-Quisser limit. This new proposed device paves the way toward high-efficiency solar cell design for light-conversion applications.