New formalism for self-consistent parameters optimization of highly efficient solar cells

Abstract

We analysed self-consistently photoconversion efficiency of direct-gap A3B5 semicon-ductors based solar cells and optimised their main physical characteristics. Using gallium ar-senide (GaAs) as the example and new efficient optimization formalism, we demonstrated that commonly accepted light re-emission and re-absorption in solar cells (SC) in technologically produced GaAs (in particular, with solid- or liquid-phase epitaxy) are not the main factors re-sponsible for high photoconversion efficiency. As we proved instead, the doping level of the base material and its doping type as well as Shockley-Read-Hall (SRH) and surface recombination velocities are much more important factors responsible for the photoconversion. We found that the maximum photoconversion efficiency (about 27% for AM1.5 conditions) in GaAs with typical parameters of recombination centers can be reached for p-type base doped at $2 \cdot 10^{17}$ cm$^{-3}$. The open circuit voltage $V_{OC}$ formation features are analyzed. The optimization provides a significant increase in $V_{OC}$ and the limiting photoconversion efficiency close to 30%. The approach of this research allows to predict the expected solar cells (for both direct-gap and indirect-band semiconductor) characteristics if material parameters are known. Obtained formalism allows to analyze and to optimize mass production both tandem solar cell (TSC) and one-junction SC parameters.