Keywords: numerical modelling, thin films, tandem solar cells, series resistance, shunt resistance, doping concentration, absorber layer thickness, light concentration, temperature
Modelling of thin–film tandem solar cells
Numerical modelling of thin–film tandem solar cells is investigated using PC–1D program. The program is adapted to simulate the performance of multi–junction solar cells. Cadmium–zinc telluride (Cd0.6Zn0.4Te) is chosen as an absorber layer material for the wide band gap top cell and copper indium diselenide (CuInSe2) is chosen as an absorber layer material for the bottom cell in the whole tandem cell structure. The effects of series resistance, shunt resistance, thickness' of the absorber layers, doping concentrations of the absorber layers, light concentration and temperature on the performance of tandem thin–film solar cells are carried out. The results indicate that the series resistance has a significant effect on the performance of the top cell compared to its effect on the bottom cell. In addition, under high light concentration conditions, the series resistance has a tremendous effect on deteriorating the cell efficiency compared to low concentration conditions. The results also indicate that the temperature change greatly affects the bottom cell more than the top cell. Finally, doping concentrations and thickness' of the absorber layers of the top and bottom cells are optimised to achieve high efficiency multi–junction cell.