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.
