Use of TCO as splitter in the optical splitting system for solar cells combination: A simulation study

Transparent conducting oxides (TCOs) are evaluated as optical splitters in combined single thin film solar cells by using theoretical considerations. The optical properties of TCOs (transmittance and reflectance) are calculated using the Drude theory for free carriers. To improve the overall efficiency of the combined solar cells, the optical properties of the TCOs are studied as a function of the electron concentration and thickness, to obtain the best fit with the external quantum efficiency (EQE) of the solar cells in each case. The optimum values of the above parameters are obtained by applying a modified version of the Hooke-Jeeves method. To validate the proposal of the use of a TCO as the splitter, the short circuit current is calculated for several combined solar cell systems and the results are compared with those obtained using more sophisticated and expensive splitters, reported in the literature. The experimental results using a commercial TCO are presented, to verify the validity and feasibility of the novel concept.