Compositional Engineering of Environment Friendly Absorber Layer for Perovskite Solar Cells /

Abstract

Lead halide-based perovskite solar cells (PSCs) have become a popular choice to dethrone existing silicon-based photovoltaic technology due to their skyrocketing efficiencies and low-cost fabrication techniques. However, as they are racing for commercialization, lead toxicity is a major obstacle standing in the way hampering their large-scale manufacturing. Recently, tin-lead (Sn-Pb) mixed perovskites have gained unprecedented attention to mitigate lead toxicity along with obtaining outstanding power conversion efficiencies. But, since with every blessing comes a burden, unfortunately, Sn-Pb mixed perovskite materials have inherited two fundamental problems from their predecessors, tin perovskites: i) facile Sn oxidation and ii) uncontrolled fast crystallization leading to the significant loss of PSCs device performance. To counter this, herein, additive engineering has been applied to ameliorate structural, optoelectronic, and morphological properties of Sn-Pb mixed perovskites. A Lewis base, caffeine (1,3,7-trimethylpurine-,2,6-dione), containing two carbonyl functional groups (C=O), is introduced which has also been extensively studied as an antioxidant in food and biotechnology. Control and caffeine doped SnPb perovskite precursors were prepared and spin-coated onto the glass substrates to prepare perovskite films. The prepared Sn-Pb perovskite films were studied using advanced characterizations techniques, i.e., X-ray diffraction, UV-visible spectroscopy, photoluminescence spectroscopy, Fourier transform infrared spectroscopy, electrochemical impedance spectroscopy, and scanning electron microscopy. The results indicate that caffeine-doped Sn-Pb perovskite films showed enhanced crystallinity, reduced trap-state density, and increased grain size implying superior structural, optoelectronic, and morphological properties as relative to the undoped Sn-Pb perovskites.