Anti-solvent engineering for efficient semitransparent CH₃NH₃PbBr₃ perovskite solar cells for greenhouse applications

With ideal combination of benefits that selectively converts high photon energy spectrum into electricity while transmitting low energy photons for photosynthesis, the CH₃NH₃PbBr₃ perovskite solar cell (BPSC) is a promising candidate for efficient greenhouse based building integrated photovoltaic (BIPV) applications. However, the efficiency of BPSCs is still much lower than their theoretical efficiency. In general, interface band alignment is regarded as the vital factor of the BPSCs whereas only few reports on enhancing perovskite film quality. In this work, highly efficient BPSCs were fabricated by improving the crystallization process of CH₃NH₃PbBr₃ with the assistance of anti-solvents. A new anti-solvent of diphenyl ether (DPE) was developed for its strong interaction with the solvents in the perovskite precursor solution. By using the anti-solvent of DPE, trap-state density of the CH₃NH₃PbBr₃ film is reduced and the electron lifetime is enhanced along with the large-grain crystals compared with the samples from conventional anti-solvent of chlorobenzene. Upon preliminary optimization, the efficiencies of typical and semitransparent BPSCs are improved to as high as 9.54% and 7.51%, respectively. Optical absorption measurement demonstrates that the cell without metal electrode shows 80% transparency in the wavelength range of 550–1000 nm that is perfect for greenhouse vegetation. Considering that the cell absorbs light in the blue spectrum before 550 nm, it offers very high solar cell efficiency with only 17.8% of total photons, while over 60% of total photons can transmit through for photosynthesis if a transparent electrode can be obtained such as indium doped SnO₂.