Super-Fast Vacuum Deposition of Complex Perovskites

Within the research field of single- and multi-junction solar cells the metal halide perovskites are becoming increasingly appealing for commercialization, primarily due to their record power conversion efficiencies (PCEs).[1][2] These PCE records are a result of several attractive qualities inherent to perovskites.[3] One of these qualities is its compositional flexibility. A large variety of hybrid compositions, including organic and inorganic precursors and dopants, have led to a range of different band gap semiconductors with increased optoelectronic performance and stability.[4] These improved properties come accompanied by an increased production complexity due to, among other things, the different volatility and solubility of its components.[5]
The most explored production method, with the largest number of publications and the current PCE record, is solution-based production.[6] Solution-based deposition techniques allow relativity easy inclusion of compatible precursors without the use of specialized or expensive equipment. [7-10]
Another method, vapor-phase deposition, in particular co-sublimation of perovskite precursors, has also been successfully shown to lead to high quality perovskite films and solar cells. [2] This method can be more seamlessly transferred into already established production lines in the semiconductor industry.[11] However, the number of precursors that can controllably and reproducibly be co-sublimed is limited. Moreover, relatively slow sublimation rates are required to maintain control over the perovskite stoichiometry, resulting in deposition times in the order of hours.
In this presentation, I will present a novel, vapor-based deposition method in which complex perovskite films with a thickness of 500 nm are deposited near stoichiometrically within one minute. The quality of the perovskite films is high with halve-stack photoluminescence quantum efficiencies reaching over 1%, and charge carrier diffusion lengths of over 500 nm. These qualities are a consequence of relatively large grain sizes in the order of micrometers and low trap state densities. Both of which are made possible by the near effortless inclusion of previously studied bulk passivators such as benzyl-phosphonic acid, methylammonium chloride and ethylenediamine iodide, applied in this method.
An area of 10x10 cm² can be deposited with each evaporation and sample replacement takes less than 15 minutes. The system does not require frequent refilling of precursors, making the total production throughput very high. The combination of the qualities above enables us to make more complex perovskites, in a stoichiometric way, faster than with conventional methods and the design is made with upscaling for commercialization in mind.