A Templating Approach to Controlling the Growth of Co-Evaporated Halide Perovskites

Metal halide perovskite semiconductors have shown significant potential for use in photovoltaic devices. While fabrication of perovskite thin-films can be achieved through a variety of different techniques, thermal vapour deposition is particularly promising, allowing for high-throughput fabrication and large-scale production. However, the ability to control the nucleation and growth of these materials, particularly at the charge-transport layer (CTL)/perovskite interface, is critical to unlocking the full potential of vapour-deposited perovskite photovoltaics, since the surface of the substrate material exerts a substantial impact beyond the interface, leading to alterations in the morphology of the entire film. As a result, for vapor-deposited perovskites, it is crucial to choose the right CTLs to ensure uniform deposition of alkylammonium halides and appropriate crystallization of the perovskite material. This not only limits the range of available substrates, but also requires extensive experimentation to optimize the evaporation parameters for different types of substrates. This issue limits the economic feasibility of industrial applications, as the most attractive scale-up technique is to produce all device layers on the same vacuum fabrication lines. Therefore, the ability to decouple the nucleation and growth of coevaporated perovskite films from the influence of substrate materials is of the utmost importance.<br/><br/>We highlight our recent work [Yan et al., ACS Energy Lett. (2023)] wherein we explored the use of a templating layer to control the growth of co-evaporated perovskite films, and found that such templating reproducibly leads to highly oriented films with identical morphology, crystal structure, and optoelectronic properties, independent of the specific substrate on which the perovskite was deposited. When incorporated into solar cells, devices based on this approach showed reproducible improvements, yielding vapour-deposited FA_0.9Cs_0.1PbI_3-xCl_x solar cells with steady-state solar-to-electrical power conversion efficiencies over 19.8%. This report provides an effective and reproducible method for controlling the buried charge transport layer/perovskite interface in vapor-deposited perovskite solar cells, further increasing the competitiveness of this deposition technique, moving the field closer to large-scale fabrication of a wide-range of efficient perovskite optoelectronic devices.<br/><br/>Yan, S. et al., A Templating Approach to Controlling the Growth of Coevaporated Halide Perovskites, ACS Energy Lett. 2023, 8, 10, 4008–4015 DOI: 10.1021/acsenergylett.3c01368