n-n Type Heterojunction Enabling Highly Efficient Carrier Separation in Inorganic Solar Cells

Carrier separation in a solar cell usually relies on the p-n junction. Here we show that n-n type inorganic semiconductor heterojunction is also able to separate the exciton for efficient solar cell applications. The n-n type heterojunction was formed by hydrothermal deposition of Sb2(S,Se)3 and thermal evaporation of Sb2Se3. We found that the n-n junction is able to enhance the carrier separation by the formation of an electric field, reduce the interfacial recombination and generate optimized band alignment. The device based on this n-n junction shows 2.89% net efficiency improvement to 7.75% when compared with the device consisted of semiconductor absorber-metal contact. The study in the n-n type solar cell is expected to bring about more versatile materials utility, new interfacial engineering strategy and fundamental findings in the photovoltaic energy conversion process.

Elucidating the Trajectory of the Charge Transfer Mechanism and Recombination Process of Hybrid Perovskite Solar Cells

Perovskite-based solar cells (PSCs) have attracted attraction in the photovoltaic community since their inception in 2009. To optimize the performance of hybrid perovskite cells, a primary and crucial strategy is to unravel the dominant charge transport mechanisms and interfacial properties of the contact materials. This study focused on the charge transfer process and interfacial recombination within the n–i–p architecture of solar cell devices. The motivation for this paper was to investigate the impacts of recombination mechanisms that exist within the interface in order to quantify their effects on the cell performance and stability. To achieve our objectives, we firstly provided a rationale for the photoluminescence and UV-Vis measurements on perovskite thin film to allow for disentangling of different recombination pathways. Secondly, we used the ideality factor and impedance spectroscopy measurements to investigate the recombination mechanisms in the device. Our findings suggest that charge loss in PSCs is dependent mainly on the configuration of the cells and layer morphology, and hardly on the material preparation of the perovskite itself. This was deduced from individual analyses of the perovskite film and device, which suggest that major recombination most likely occur at the interface.