Abstract
Based upon the quasi-equilibrium approximation, the validity of p-n junction modelling, has been experimentally investigated under synchronous electrical and optical excitation of silicon photo-diodes. The devices had areas of 8.2 mm2 and reverse bias saturation currents of the order of 10-10 A. Their current-voltage (I-V) response was exploited experimentally both in the dark and under various illumination levels. The quoted values for the saturation current, the ideality factor, the series resistance and the reverse-bias photocurrent are investigated for the simulation of the I-V curves via the quasi-equilibrium model. In addition, the measured I-V data have been further analysed to estimate the produced photocurrent as a function of the applied bias (forward or reverse) under given illumination levels. Comparisons between the simulated curves and the experimental data allowed a detailed photocurrent modelling validation. The proposed approach could be useful towards studying other parameters of optically activated p-n junctions such as: the bias dependence of the minority carrier diffusion lengths and/or the generated rates of electron-hole pairs (EHP).
Highlights
The modelling of photovoltaics is frequently employed by researchers in the field towards further analysis and understanding interactions between light and matter [1,2,3,4]
The quoted values for the saturation current, the ideality factor, the series resistance and the reverse-bias photocurrent are investigated for the simulation of the I-V curves via the quasi-equilibrium model
The proposed approach could be useful towards studying other parameters of optically activated p-n junctions such as: the bias dependence of the minority carrier diffusion lengths and/or the generated rates of electron-hole pairs (EHP)
Summary
The modelling of photovoltaics (system or devices) is frequently employed by researchers in the field towards further analysis and understanding interactions between light and matter [1,2,3,4]. Recombination effects developing either within the depletion layer width (w) or within the minority carrier diffusion lengths at each side of the p-n junction (Ln, Lp) contribute significantly to the overall current flow across the barrier and affect forward and reverse I-V characteristics. The presence of recombination centers affects the overall current-voltage characteristics by the generation of additional electron-hole pairs within the depletion layer width. Their generation rate, U, has been studied in the theory proposed by Shockley and Read, which after certain simplifying assumptions, leads to the following equation [11]: U σ .υ th .N T .ni 2. The proposed experimental approach might be useful towards the investigation of such statements
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