Electro-analytical characterization of photovoltaic cells by combining voltammetry and impedance spectroscopy: voltage dependent parameters of a silicon solar cell under controlled illumination and temperature

摘要

This work reports a detailed electro-analytical framework for direct determination of a broad range of performance-indicator parameters of silicon solar cells. A mono-crystalline Si cell, equipped with the efficiency-boosting back surface field (BSF) feature, is used as a model system for this study. Independently controlled illumination (0-1 Sun, from a solar simulator) and temperature of the cell prevent the interference of photothermal and photovoltaic processes during the measurements. The technique of D.C. voltammetry is employed to obtain current-voltage plots, fill-factors, efficiencies and effective cell resistances. The same experimental platform also supports A.C. impedance spectroscopic probing of the solar cell, which, in combination with complex nonlinear least square analysis of the experimental data, provides detailed information about both the emitter-base and the BSF components of the photovoltaic device. These impedance measurements lead to straightforward determination of the diffusion and depletion layer capacitances, diode resistance, series resistance, concentration of majority carriers as well as lifetime of minority carriers in the base, resistance and capacitance of the BSF junction, and relaxation time of holes in the BSF. The results presented here demonstrate how relatively simple electro-analytical experiments can be strategically utilized for quantitative characterization of photovoltaic systems.