A theoretical approach on the strain-induced dislocation effects in the quantum dot solar cells

Abstract

Abstract The numbers of the quantum dot layers that can be embedded in the active region of the quantum dot intermediate band solar cells affects on the photocurrent and also can produce strain-induced dislocations in the cell. To enhance the absorption of the low energy photons in the system, the number of the quantum dot layers needs to be increased, but in this way, dislocations and defects of the cell non-radiative recombination will also increase. In this paper, the characteristics of intermediate band solar cells containing 10, 20, and 50 InAs quantum dot layers embedded in the active region of the cells have been considered and compared. There are an optimum number of quantum dot layers for significant absorption of low energy photons. Furthermore, for a cell with 10 QD layers, the current–voltage characteristics and internal quantum efficiency have been investigated for different values of minority carriers recombination lifetimes (or diffusion lengths) and electron filling factors. Electron filling factor, gives a design constraints for the size of the quantum dots and distance between the layers. The results showed that the perfect cells need to be considered from two aspects; first, from the optimum number of the quantum dot layers to control the strain-induced dislocations that produce non-radiative recombinations and reduce the photocurrent and second, the dots spacing and size that need to be justified for wavefunction penetration into barrier region that reduces the non-radiative recombinations.