Triple Halide Perovskite Absorbers for >27% Perovskite/Silicon Tandem Solar Cells with Excellent Stability

Wide bandgap metal halide perovskites are promising candidates to pair with low bandgap silicon, copper indium gallium diselenide, or perovskite photovoltaics for highly efficient next-generation tandems due to excellent optoelectronic properties, low-cost manufacturability, and bandgap tunability. Here, we alloy chlorine into the perovskite lattice to create a triple halide wide bandgap perovskite absorber, a phase space that has thus far been overlooked. We show that chlorine is incorporated into the lattice in molar amounts up to 15%. The addition of chlorine doubles the charge carrier mobilities and lifetimes of the material. We show that a 1.67 eV triple halide perovskite does not experience photoinduced halide phase segregation under intensities up to 100 suns. Finally, we incorporate triple halide perovskite into solar cells, obtaining single junction devices with open-circuit voltages >1.2 V and >20% efficiency, and monolithic perovskite/silicon tandem solar cells with voltages approaching 1.9 V and >27% efficiency. Solar cells with the triple halide perovskite absorber retain 95% of their initial efficiency under maximum power point tracking at 60°C under white light illumination for 1000 hours.

Mike McGehee is a Professor in the Chemical and Biological Engineering Department at the University of Colorado Boulder.  He is the Associate Director of the Materials Science and Engineering Program and has a joint appointment at the National Renewable Energy Lab.  He was a professor in the Materials Science and Engineering Department at Stanford University for 18 years and a Senior Fellow of the Precourt Institute for Energy.  His current research interests are developing new materials for smart windows and solar cells. He has previously done research on polymer lasers, light-emitting diodes and transistors as well as transparent electrodes made from carbon nanotubes and silver nanowires. His group makes materials and devices, performs a wide variety of characterization techniques, models devices and assesses long-term stability.  He received his undergraduate degree in physics from Princeton University and his PhD degree in Materials Science from the University of California at Santa Barbara.