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One-dimensional analytical model for photovoltaic cells based on wide gap semiconductors

S. S. GEORGIEV1,* , Tz. E. IVANOV1

Affiliation

  1. Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tzarigradsko Chaussee Blvd., 1784 Sofia, Bulgaria

Abstract

One-dimensional analytical model suitable for large scale cells under illumination has been developed. The model is based on two main assumptions. The first one is that in the case of wide gap semiconductors the concentration of the free dark carriers related to the non-equilibrium (generated) carriers can be neglected. This assumption simplifies the transport equations. In the second one, we assume an mean value (Egc) of the electrical field across the i-layer in accordance with the relationship ( = ∫ w gc gxE w E dx 0 ) were Egx is the field created by light generated charges, w is the thickness of the i-layer of the cell. These assumptions allow us to transform the system from continuity and transport equations in a first order differential equation that simplify the solution of the system. The experimental solar cell characteristics are fitted using the finite number of fundamental parameters, namely the electron and hole diffusion lengths (ln ands lp, respectively), the light intensity (L0) and light absorption coefficient (α). If we know the values of L0 and α, we can derive from the fitted curve the lp value with satisfactory accuracy. The value of ln influences more weakly on the I-V dependence. A simple formula for optimal thickness of the i-layer of the cell is derived..

Keywords

Physical modeling, Thin film solar cell, a-Si:H, a-Si:Ge:H, Diffusion length.

Submitted at: Dec. 7, 2012
Accepted at: Jan. 22, 2014

Citation

S. S. GEORGIEV, Tz. E. IVANOV, One-dimensional analytical model for photovoltaic cells based on wide gap semiconductors, Journal of Optoelectronics and Advanced Materials Vol. 16, Iss. 1-2, pp. 41-46 (2014)