Rapid microwave annealing of perovskite films: exploring the mechanism of heat generation and influence on growth kinetics

Perovskite solar cells have gained significant attention in both research and industry due to their simple manufacturing process, low cost, abundance of constituent materials, and high-power conversion efficiency. Thermal annealing is crucial for achieving optimal crystal growth in perovskite films. Recently, microwave processing has emerged as a rapid and energy-efficient alternative to conventional hotplate annealing. By using microwave annealing, we reduced processing time to one-tenth of the traditional methods while simultaneously enhancing crystal quality. However, the underlying heat generation mechanism remains unclear, requiring further investigation to optimise the process and enable widespread adoption of this scalable technology. This work explores microwave absorption and heat generation mechanisms in rapidly grown MAPbI₃ perovskite films. Through simulations and experiments, we model the role of dielectric absorption and eddy current heating in perovskite/glass and perovskite/FTO layers, supported by structural, optical and electrical characterisation. Furthermore, we successfully mitigated the edge effect caused by electromagnetic wave diffraction, a common limitation of microwave annealing of semiconductors. We expanded classical nucleation theory with microwave-specific modifications, establishing a comprehensive framework that links microwave power to nucleation rates and grain growth. This work provides critical insights into optimising microwave processing parameters, advancing rapid thermal techniques for scalable, high-throughput perovskite solar cell manufacturing.