Benefit of Grain Boundaries in Organic–Inorganic Halide Planar Perovskite Solar Cells

The past 2 years have seen the uniquely rapid emergence of a new class of solar cell based on mixed organic–inorganic halide perovskite. Grain boundaries are present in polycrystalline thin film solar cell, and they play an important role that could be benign or detrimental to solar-cell performance. Here we present efficient charge separation and collection at the grain boundaries measured by KPFM and c-AFM in CH₃NH₃PbI₃ film in a CH₃NH₃PbI₃/TiO₂/FTO/glass heterojunction structure. We observe the presence of a potential barrier along the grain boundaries under dark conditions and higher photovoltage along the grain boundaries compare to grain interior under the illumination. Also, c-AFM measurement presents higher short-circuit current collection near grain boundaries, confirming the beneficial roles grain boundaries play in collecting carriers efficiently

CsPbIBr₂ Perovskite Solar Cell by Spray-Assisted Deposition

In this work, an inorganic halide perovskite solar cell using a spray-assisted solution-processed CsPbIBr₂ film is demonstrated. The process allows sequential solution processing of the CsPbIBr₂ film, overcoming the solubility problem of the bromide ion in the precursor solution that would otherwise occur in a single-step solution process. The spraying of CsI in air is demonstrated to be successful, and the annealing of the CsPbIBr₂ film in air is also successful in producing a CsPbIBr₂ film with an optical band gap of 2.05 eV and is thermally stable at 300 °C. The effects of the substrate temperature during spraying and the annealing temperature on film quality and device performance are studied. The substrate temperature during spraying is found to be the most critical parameter. The best-performing device fabricated using these conditions achieves a stabilized conversion efficiency of 6.3% with negligible hysteresis. Cesium metal halide perovskites remain viable alternatives to organic metal halide perovskites as the cesium-containing perovskites can withstand higher temperature

Nucleation and Growth Control of HC(NH₂)₂PbI₃ for Planar Perovskite Solar Cell

HC­(NH₂)₂PbI₃ perovskite solar cells have emerged as a promising alternative to CH₃NH₃PbI₃ perovskite solar cells due to their better thermal stability and lower bandgap. In this work, we have demonstrated a reliable fabrication technique for HC­(NH₂)₂PbI₃ planar perovskite solar cells by controlling nucleation and crystallization processes of the perovskite layer through a combination of gas-assisted spin coating and the addition of HI additive in the perovskite precursor. A narrow distribution of power conversion efficiencies (PCEs) can be achieved with an average of 13% with negligible hysteresis when measured at a scanning rate of 0.1 V/s. The best performance device has a PCE of 16.0%. It is shown that by using optimized conditions we can consistently form dense, uniform, pinhole-free good crystalline, lead-iodide-impurities-free HC­(NH₂)₂PbI₃ film that has been comprehensively characterized by scanning electron microscopy, X-ray diffraction, Kelvin probe force microscopy, photoluminescence, and electroluminescence in this work

High-Efficiency Rubidium-Incorporated Perovskite Solar Cells by Gas Quenching

We apply gas quenching to fabricate rubidium (Rb) incorporated perovskite films for high-efficiency perovskite solar cells achieving 20% power conversion efficiency on a 65 mm² device. Both double-cation and triple-cation perovskites containing a combination of methylammonium, formamidinium, cesium, and Rb have been investigated. It is found that Rb is not fully embedded in the perovskite lattice. However, a small incorporation of Rb leads to an improvement in the photovoltaic performance of the corresponding devices for both double-cation and triple-cation perovskite systems