Impact of heavy hole levels on the photovoltaic conversion efficiency of In Ga1−N/InN quantum dot intermediate band solar cells

We report a theoretical investigation of the photovoltaic conversion efficiency of solar cells based on the introduction of InxGa1−xN/InN quantum dot supracrystals arrayed in the i-region of a p−i−n photodiode. The position and width of intermediate bands induced by the discrete quantized energy levels of electrons and holes originating from QDs are determined by using the Kronig-Penney model. Thus, interband and intersubband transitions are determined for different dot sizes and inter-dot distances. Taking into account the hole level and its impact on the band offset usually neglected in the same studies, all characteristic parameters of the cell such as open circuit voltage, short circuit current density and photoelectric conversion efficiency are determined as a function of the In-concentration, mean size and inter-dot spacing of QDs. The results show that the performances of this new generation of solar cell increase considerably and can be adjusted by controlling the size, inter-dot spacing and In-concentration.