Development of wide bandgap perovskites for next-generation low-cost CdTe tandem solar cells

To continue towards long-term reduction in the price of energy generated by photovoltaic (PV) solar cells, technological innovations are needed to achieve significant increases in device efficiency without increasing manufacturing costs. One approach is to utilize the existing capability to manufacture thin film CdTe PVs at very low cost and add another inexpensive thin film absorber to create a tandem solar cell to improve device efficiency. For this, a semiconductor with an optimal bandgap must be identified, along with a suitable device architecture. The wide bandgap perovskite methylammonium lead bromide (CH3NH3PbBr3, MAPBr) has a well-matched band gap of 2.3 eV for a CdTe tandem device. It can be processed at relatively low temperature, and is also suitable for CIGS and all-perovskite tandems. We fabricated MAPBr PVs and found that optical scattering, or haze, was significant in these perovskite layers. This limits the transmitted light reaching the bottom cell. The performance of a four-terminal (4T) perovskite-CdTe tandem cell was modeled using the 1D Solar Cell Capacitance Simulator (SCAPS) software package to determine how much haze could be tolerated and still achieve an efficiency boost compared to the CdTe cell. (C) 2019 Elsevier Ltd. All rights reserved.