Low-temperature quasi-static seeded columnar grain growth of thick perovskite films with minimal stress for sensitive X-ray detection

Abstract

The large difference in the thermal expansion coefficients of lead halide perovskites and the substrates results in delamination during the thermal annealing process, which hinders the application of thick perovskite film-based X-ray detectors. To mitigate interfacial thermal stress and film cracking in perovskite thick films, we developed a quasi-static blade-coating method by utilizing induced crystal growth from the saturated precursor solution at low temperature. By using the highly volatile solvent 2-methoxyethanol in an air-assisted coating process, an orderly and slow columnar grain growth of perovskite thick films on a seed layer was achieved at only 40 °C. This near-equilibrium growth minimizes internal stress, resulting in MAPbI₃ films with large columnar grains, low pinhole density, and strong substrate adhesion without cracking. The assembled X-ray detector exhibits a sensitivity of 2891.8 µC Gy_air⁻¹ cm⁻² at a bias of 2.5 V and under 40 kV X-ray irradiation. This work provides a scalable, low-temperature route to control the stress between perovskite thick films and the substrates for high-performance radiation detection.