Abstract
The organic-inorganic lead halide perovskite layer is a crucial factor for the high performance perovskite solar cell (PSC). We introduce CH3NH3Br in the precursor solution to prepare CH3NH3PbI3−xBrx hybrid perovskite, and an uniform perovskite layer with improved crystallinity and apparent grain contour is obtained, resulting in the significant improvement of photovoltaic performance of PSCs. The effects of CH3NH3Br on the perovskite morphology, crystallinity, absorption property, charge carrier dynamics and device characteristics are discussed, and the improvement of open circuit voltage of the device depended on Br doping is confirmed. Based on above, the device based on CH3NH3PbI2.86Br0.14 exhibits a champion power conversion efficiency (PCE) of 18.02%. This study represents an efficient method for high-performance perovskite solar cell by modulating CH3NH3PbI3−xBrx film.
Highlights
Recent years, the solar cells based on organic-inorganic lead halide perovskite are considered as one of the most important developments in the field of solar energy due to their many advantages including low cost, facile preparation process, good stability and high power conversion efficiency (PCE)[1,2,3,4], organic-inorganic lead halide perovskite unique feature such as broad and strong light absorption[5], longer carrier lifetimes[6], long charge carrier diffusion length[7,8], and low exciton binding energy[9]
The power conversion efficiencies of the perovskite solar cells based on CH3NH3PbI3−xBrx are still lower[21]
We introduce CH3NH3Br in the precursor solution to prepare mixed methylammonium lead halide CH3NH3PbI3−xBrx, which results in the significant improvement of photovoltaic performance of perovskite solar cell (PSC)
Summary
It can be seen that with the increase of Br amount from CH3NH3PbI3 to CH3NH3PbI2Br, the absorption edges of the hybrid perovskite films shift towards the shorter wavelength[33]. According to the literatures[34,35,36] and the energy level principle[2,3,12,37,38], with the increase of Br amount in CH3NH3PbI3−xBrx the conduction band of the perovskite ascends and the valence band descends, resulting in the absorption edge shifted towards to shorter wavelength, which indicates the formation of wider energy band and a higher photovoltage (VOC) of the device. The device based on CH3NH3PbI2.86Br0.14 film possesses superior charge injection characteristics and low internal resistance, resulting in better photovoltaic performance than others. The device based on CH3NH3PbI2.86Br0.14 achieves a champion PCE of 18.02% with a stabilized output efficiency of 17.68% at the maximum power point
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