Bifunctional Polymer-Assisted Growth of Crack-Free Thick Perovskite Films for Flexible X-ray Detection

Qianrui Li^a, Donato Valli^a,b, Elke Debroye^a*

^a Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001, Heverlee, Belgium.

^b Institute of Supramolecular Science and Engineering (ISIS), Strasbourg, Grand Est, France

E-mail: qianrui.li@kuleuven.be

The expanding use of perovskite materials in flexible optoelectronics has sparked growing interest in their application for flexible X-ray detectors. However, developing flexible, lead-free perovskite devices remains challenging because achieving the film thickness required for strong X-ray absorption typically leads to cracking and poor device reliability.^[1]

In this presentation, I will introduce a bifunctional polymer-guided crystallization strategy to resolve the intrinsic trade-off between thickness, mechanical integrity, and charge transport continuity in Cs₂AgBiBr₆ thick films. P123 is composed of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG), to simultaneously control crystallization and enhance the mechanical integrity of lead-free Cs₂AgBiBr₆ thick films. We demonstrated that PEG modulates precursor coordination and intermediate-phase evolution, suppressing uncontrolled nucleation, while the PPG prevents excessive Ag⁺ binding and stabilizes uniform long-range crystal growth. Together, these two molecular interactions establish a self-regulated crystallization environment that produces uniform, highly ordered, and mechanically resilient Cs₂AgBiBr₆ thick films approaching 100 µm.

The resulting P123-modified Cs₂AgBiBr₆ detectors deliver a remarkable X-ray sensitivity of 244.71 μC Gy⁻¹ cm⁻² under a low bias of 50 V mm⁻¹, more than twice that of unmodified devices based on Cs₂AgBiBr₆ microcrystals.^[2] Moreover, the detectors maintained over 70% of their initial sensitivity under small bending radii and over 80% after 500 bending cycles, exhibiting outstanding fatigue endurance and long-term stability over a 60-day period, in contrast to the pronounced degradation seen in pristine Cs₂AgBiBr₆ devices. This study establishes a polymer-guided design paradigm for fabricating lead-free, flexible, and scalable perovskite-based radiation detectors.

[1] I. López-Fernández, D. Valli, C.-Y. Wang, S. Samanta, T. Okamoto, Y.-T. Huang, K. Sun, Y. Liu, V. S. Chirvony, A. Patra, J. Zito, L. De Trizio, D. Gaur, H.-T. Sun, Z. Xia, X. Li, H. Zeng, I. Mora-Seró, N. Pradhan, J. P. Martínez-Pastor, P. Müller-Buschbaum, V. Biju, T. Debnath, M. Saliba, E. Debroye, R. L. Z. Hoye, I. Infante, L. Manna and L. Polavarapu, Advanced Functional Materials 2024, 34, 2307896.

[2] L. Clinckemalie, R. A. Saha, D. Valli, E. Fron, M. B. J. Roeffaers, J. Hofkens, B. Pradhan and E. Debroye, Advanced Optical Materials 2023, 11, 2300578.