Detailed Investigation of Evaporated Perovskite Absorbers with High Crystal Quality on Different Substrates

Abstract

Dual-source vapor-phase deposition enables low-temperature fabrication of high-performance planar structure perovskite (CH₃NH₃PbI₃) solar cells (PSCs), applicable in tandem devices or for industrial production with high homogeneity. Herein, we report low-temperature fabrication of high-efficiency PSCs by dual-source vapor-phase deposition and significance of TiO₂ surface modification with [6,6]-phenyl C₆₁ butyric acid methyl ester (PCBM) on cell performance. Co-evaporation of PbI₂ and CH₃NH₃I, as confirmed by X-ray diffraction and high-resolution transmission electron microscopy analyses, results in CH₃NH₃PbI₃ layers with a well-crystallized tetragonal phase formed on both TiO₂ and TiO₂/PCBM electron-transport layers (ETLs). The devices with PCBM interlayer between TiO₂ and CH₃NH₃PbI₃ showed remarkably higher performance than those with TiO₂ only, which was attributed to enhance charge extraction and reduced recombination at the TiO₂/PCBM/CH₃NH₃PbI₃ interface. The devices composed of evaporated CH₃NH₃PbI₃ on top of the TiO₂/PCBM and [2,2',7,7'-tetrakis( N, N-di- p-methoxyphenyl-amine)-9,9'-spirobifluorene] (Spiro-OMeTAD) as hole-transport material demonstrated power conversion efficiencies of 17.1% (reverse scan) and 13.4% (forward scan) with stabilized efficiency of over 16%, which is, to the best of our knowledge, the highest efficiency reported for evaporated perovskite solar cells using low-temperature fabrication method involving compact TiO₂ layer as ETL. Furthermore, we show that this process can be used to deposit a CH₃NH₃PbI₃ layer on top of a textured silicon substrate, which is the first step for preparing perovskite-silicon tandem devices with enhanced antireflection and light-trapping properties.