Micro-Processing Stable Optoelectronic Perovskite Thin Films

All-inorganic CsPbI3 perovskite is increasingly being considered for applications well beyond photovoltaics, for example, as the active regions within thin film photonic devices like cameras and LEDs. Its high-temperature optically active black phase (>320°C) is metastable relative to its non-perovskite yellow phase at room temperature (RT), representing a major impediment for real-world applications. In 2019, a fundamentally new and effective stabilization approach was developed by the applicant to secure a RT black phase, based on micro-processing. The method patterns the surface with a micrometer-scale grid via direct visible laser writing, rendering an ambient-stable black phase, a result which strictly goes against current mainstream knowledge. To rationalise this discovery and foster device-readiness, this project aims to comprehensively understand the stabilization mechanism at play and explore realistic scale-up options. The structure-property relationships promoting stability will be studied using an advanced tool set, to probe phase thermodynamics, chemistry, micro-structure, morphology and photophysics. Ab initio materials modeling will help isolate targeted environments which stabilize the black phase, yielding general design principles and a device readiness framework; from lowering the CsPbI3 annealing temperature and scaling up clean-room microfabrication (masked UV-VIS and X-ray lithography), to prototyping photonic devices based on the novel discovery.