Enhanced performance of ultrathin n-i-p and p-i-n perovskite solar cells via light trapping: a simulation study employing Lambertian back reflector

Abstract

In this study, the effectiveness of a Lambertian back reflector for trapping light in a MAPbI3 perovskite solar cell has been investigated. The propagation of collimated and diffuse light in the cell has been modelled using the transfer-matrix method and the radiative transfer equation respectively. We show that in the presence of such a reflector, the population of tail states at wavelengths beyond the band-edge of a conventional cell can be substantially increased. As a result of this enhanced light absorption, the power conversion efficiency of a 600 nm thick active layer in a conventional n-i-p (p-i-n) cell is shown to be attainable with a reduced thickness of 300 nm (200 nm) in the presence of light trapping. The effect of photon recycling to increase the open circuit voltage in these structures has also been studied for different thicknesses of the active layer. An increased open circuit voltage in the range 125-145 mV is observed for a Lambertian back reflector as compared to155-170 mV increase seen in a conventional cell with metallic back reflector.