Simulations of the intermediate bandwidth fluctuations in nanostructured PV

The size dispersion and distributions of quantum dot nanoparticles (sizes from 2–5 nm) embedded in the active region of the intermediate band solar cells are important to reach the high efficiencies. An optimized size and regularity can increase the efficiency due largely to avoided non-radiative transitions which can originate from the fluctuations in the bandwidth of the intermediate layer. In this work, we propose all the energy band diagrams possible in the formation of such a cell. Five equivalent band diagrams of the cells with different size dispersions and regularity of quantum dots are considered and compared with the reported experimental profiles in the literature. Furthermore, the degree of the size fluctuation is considered by proposing a fluctuation degree for the band gap and sub-band gaps of the cell. These proposed profiles and the fluctuation theory are exploited to consider the experimental data reported in literature. The optimized size dispersion will increase the photocurrent of the cell. We believe that every quantum dot solar cell will fall into one of the proposed band diagrams. This approach gives foresight to the theoretical studies of such devices and expectation from the energy band structure and band widths since it considers the fluctuation of the band widths for the intermediate band separately.