Simulated performance of monocrystalline CdTe/MgCdTe double heterostructure solar cells

Abstract

This paper reports the simulated performance of monocrystalline CdTe/MgCdTe double-heterostructure solar cells using both the detailed-balance model and the drift-diffusion model. The Shockley-Queisser model predicts the limiting efficiency of an idealized solar cell with unity absorptance above the bandgap energy and zero below. However, practical solar cells do not have step-function absorptance spectra due to finite absorber thickness, non-ideal anti-reflection coating, Urbach tail, etc. This paper develops a detailed-balance model for solar cells with finite absorber thicknesses and arbitrary absorptance spectra, which can be calculated using the material property and sample structure of a solar cell. The drift-diffusion model is solved numerically using PC1D software while taking into account the photon recycling (PR) effects by adjusting the effective radiative recombination coefficient with a PR factor of the solar cell. With the inclusion of the PR effect, simulation results from PC1D agree well with the detailed-balance limit when non-radiative recombination is negligible. The expected efficiencies of a monocrystalline CdTe/MgCdTe double-heterostructure solar cell are calculated as a function of minority carrier lifetime. A 28.7 % efficiency is potentially achievable for monocrystalline CdTe/MgCdTe DH solar cells with a SRH lifetime of 2.7 µs demonstrated very recently.