Characteristics of Perovskite Solar Cells with ZnGa₂O₄:Mn Phosphor Mixed Polyvinylidene Fluoride Down-Conversion Layer

To reduce the manufacturing cost of perovskite solar cells, soda-lime glass and transparent conducting oxides such as indium tin oxide and fluorine-doped tin oxide are the most widely used substrates and lighttransmitting electrodes. However, the transmittance spectra of soda-lime glass, indium tin oxide, and fluorinedoped tin oxide show that all light near and below 330 nm is absorbed; thus, with the use of these substrates, light energy near and below 330 nm cannot reach the perovskite light-absorbing layer. It is expected that the overall solar cell can be improved if the wavelength can be adjusted to reach the perovskite solar cell absorbing layer through down-conversion of energy in the optical wavelength band. In this study, a polyvinylidene fluoride transparent film mixed with a ZnGa₂O₄:Mn phosphor was applied to the incident side of the perovskite solar cell with the intent to increase the light conversion efficiency without changing the internal bandgap energy and structure. By adding a phosphor layer to the external surface of PSC exposed to incident light, the efficiency of the cell was increased by the down-conversion of ultraviolet light (290 nm) to the visible region (509 nm) while maintaining the transmittance. To manufacture the perovskite solar cell, a TiO₂-based mesoporous electron transport layer was spin-coated onto the substrate. The perovskite layer used in this experiment was CH₃NH₃PbI₃ and was fabricated on a TiO₂ layer. Spiro-OMeTAD solution was spin-coated as a hole-transport layer.