High-effciency inverted semi-transparent planar perovskite solar cells in substrate configuration

The ability to grow perovskite solar cells in substrate configuration, where light enters the devices from the film side, allows the use of non-transparent flexible polymer and metal substrates. Furthermore, this configuration could facilitate processing directly on Cu(In, Ga) Se-2 solar cells to realize ultrahigh-effciency polycrystalline all-thin-film tandem devices. However, the inversion of conventional superstrate architecture imposes severe constraints on device processing and limits the electronic quality of the absorber and charge selective contacts. Here we report a device architecture that allows inverted semitransparent planar perovskite solar cells with a high open-circuit voltage of 1.116V and substantially improved effciency of 16.1%. The substrate configuration perovskite devices show a temperature coeffcient of -0.18% degrees C-1 and promising thermal and photo-stability. Importantly, the device exhibits a high average transmittance of 80.4% between 800 and 1,200 nm, which allows us to demonstrate polycrystalline all-thin-film tandem devices with effciencies of 22.1% and 20.9% for Cu(In, Ga) Se-2 and CuInSe2 bottom cells, respectively.