Characterization and optimization of high-efficiency crystalline silicon solar cells

TL;DR

This paper develops a comprehensive theoretical model for high-efficiency crystalline silicon solar cells, including additional recombination mechanisms, to optimize their parameters and enhance their photoconversion efficiency beyond current records.

Contribution

It introduces a new analytical formalism incorporating additional recombination processes and a simple wavelength-dependent EQE model for better optimization of silicon solar cells.

Findings

The model accurately predicts efficiency based on cell thickness and doping.

Application to existing cells shows potential for efficiency improvements.

The formalism enables further optimization of solar cell design parameters.

Abstract

Since the photoconversion efficiency $\eta$ of the silicon-based solar cells (SCs) under laboratory conditions is approaching the theoretical fundamental limit, further improvement of their performance requires theoretical modeling and/or numerical simulation to optimize the SCs parameters and design. The existing numerical approaches to modeling and optimization of the key parameters of high-efficiency solar cells based on monocrystalline silicon (c-Si), the dominant material in photovoltaics, are described. It is shown that, in addition to the four usually considered recombination processes, namely, Shockley-Read-Hall, surface, radiative, and band-to-band Auger recombination mechanisms, the non-radiative exciton Auger recombination and recombination in the space charge region (SCR) have to be included. To develop the analytical SC characterization formalism, we proposed a simple expression to model the wavelength-dependent external quantum efficiency (EQE) of the photocurrent near the absorption edge. Based on this parameterization, the theory developed allows for calculating and optimizing the base thickness-dependent short-circuit current, the open-circuit voltage, and the SC photoconversion efficiency. We proved that the approach to optimize the solar cell parameters, especially its thickness and the base doping level, is accurate and demonstrated for the two Si solar cells reported in the literature, one with an efficiency of 26.7 % and the other with the record efficiency of 26.81 %. It is shown that the formalism developed allows further optimization of the solar cell thickness and doping level, thus increasing the SC efficiency to an even higher value.