Abstract
Halide perovskites of the form ABX3 have shown outstanding properties for solar cells. The highest reported compositions consist of mixtures of A-site cations methylammonium (MA), formamidinium (FA) and cesium, and X-site iodide and bromide ions, and are produced by solution processing. However, it is unclear whether solution processing will yield sufficient spatial performance uniformity for large-scale photovoltaic modules or compatibility with deposition of multilayered tandem solar cell stacks. In addition, the volatile MA cation presents long-term stability issues. Here, we report the multisource vacuum deposition of FA0.7Cs0.3Pb(I0.9Br0.1)3 perovskite thin films with high-quality morphological, structural, and optoelectronic properties. We find that the controlled addition of excess PbI2 during the deposition is critical for achieving high performance and stability of the absorber material, and we fabricate p-i-n solar cells with stabilized power output of 18.2%. We also reveal the sensitivity of the deposition process to a range of parameters, including substrate, annealing temperature, evaporation rates, and source purity, providing a guide for further evaporation efforts. Our results demonstrate the enormous promise for MA-free perovskite solar cells employing industry-scalable multisource evaporation processes.
Highlights
Halide perovskites of the form ABX3 have shown outstanding properties for solar cells
We identify that the resulting film quality is highly sensitive to a number of experimental parameters, including substrate surface, source purities, relative evaporation rates between the sources, and annealing temperature, highlighting critical parameters that need global consideration for further device developments
We found that the optimal film structure and morphology was attained by inclusion of a small excess of PbI2, which led to higher photoluminescence quantum efficiencies (PLQEs) and longer charge carrier lifetimes
Summary
Research Council (ERC) (Grant Agreement No 756962 [HYPERION]) and the Marie Skłodowska-Curie actions. C.; Bolink, Horizon 2020 research and innovation programme. The authors acknowledge the Engineering and Physical Research Council (EPSRC) (EP/ R023980/1) and the EPSRC “Centre for Advanced Materials for Integrated Energy Systems (CAM-IES)” (EP/P007767/1). Thermal Degradation of CH3NH3PbI3 Perovskite into NH3 and CH3I Gases Observed by Coupled Thermogravimetry−Mass Spectrometry Analysis. MethylammoniumFree, High-Performance, and Stable Perovskite Solar Cells on a Planar Architecture. C.; Brunetti, F.; Bulovic,́ V.; Burlingame, Q.; Di Carlo, A.; for useful discussions
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