# Bifunctional polymer assisted growth of crack-free thick perovskite films for flexible X-ray detection

## TL;DR

A new polymer method creates crack-free, flexible perovskite films for X-ray detection with high sensitivity and durability.

## Contribution

A bifunctional polymer approach enables crack-free, lead-free perovskite films with enhanced mechanical and X-ray detection properties.

## Key findings

- P123-modified CABB detectors achieved 244.71 µC Gy−1 cm−2 X-ray sensitivity and 121 nGy s−1 detection limit.
- Modified films retained over 70% sensitivity under bending and 80% after 500 cycles.
- Devices showed long-term stability over 60 days, unlike unmodified versions.

## Abstract

The expanding use of perovskite materials in flexible optoelectronics has sparked growing interest in their application for flexible X-ray detectors. Achieving thick perovskite films is crucial for effective X-ray absorption; however, such films typically exhibit brittleness and crack formation. In this work, we present a bifunctional polymer-assisted approach employing the triblock copolymer Pluronic P123, composed of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG), to simultaneously control crystallization and enhance the mechanical integrity of lead-free Cs2AgBiBr6 (CABB) thick films. The PEG segments coordinate selectively with Ag+ ions, guiding evolution to the stable 3D phase, while the PPG segments introduce steric effects that mitigate excessive Ag+ coordination and favor uniform crystal growth. This cooperative mechanism yields crack-free, highly crystalline, and mechanically flexible perovskite films. The resulting P123-modified CABB detectors demonstrate a remarkable X-ray sensitivity of 244.71 µC Gy−1 cm−2 and low detection limit of 121 nGy s−1 under a low bias of 50 V mm−1, over twice that of unmodified devices. Moreover, the modified 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 CABB devices. This study establishes a polymer-guided design paradigm for fabricating lead-free, flexible, and scalable perovskite-based radiation detectors.

Pluronic P123 regulates crystallization of lead-free Cs2AgBiBr6, yielding crack-free, flexible thick films. PEG–Ag+ coordination and PPG steric effects enable uniform growth. Devices show high sensitivity, low detection limit, strong bending durability, and long-term stability.