Compact and Large‐Area Perovskite Films Achieved via Soft‐Pressing and Multi‐Functional Polymerizable Binder for Flat‐Panel X‐Ray Imager

Abstract

Thanks to its strong X-ray absorption and large carrier diffusion length, perovskites have demonstrated excellent performance for X-ray detection. Combination of perovskite with thin-film transistor (TFT) arrays to construct flat-panel X-ray imager (FPXI) is required for X-ray imaging, yet this is rarely reported. Solution processing of perovskite thick film onto TFT can enable the electronic connection, however the amounts of pinholes inevitably form during the solvent evaporation and result in a porous film with deteriorated performance and stability. Here a novel strategy is raised to achieve high-quality perovskite thick films for TFT integration via soft-pressing and in situ polymerization of multi-functional binder (TMTA). The combined process largely eliminates the pinholes, improves the surface smoothness, passivates grains boundaries, reduces ionic migration, and improves stability. Accordingly, a compact and smooth MAPbI 3 thick film integrating with TFT arrays is prepared for flat-panel X-ray imaging. The largest film (28 × 28 cm 2 ) is obtained with the state-of-theart performance (ratio of sensitivity to noise current: 1.41 × 10 11 µC Gy −1 A −1 ) among polycrystalline films. It is hoped that the work provides guidance for fabricating compact perovskite thick films and push perovskite FPXI one step further for low-dose X-ray imaging.

Scalable Fabrication of Metal Halide Perovskites for Direct X-ray Flat-Panel Detectors: A Perspective

“…To address these issues, Xia et al introduced soft-pressing as a post-treatment (Figure 3e). 38 In this study, the pores in the blade-coated perovskite films were reduced by pressing the film under 2 MPa, with no damage to the TFT array (Figure 3f, g). They also introduced trimethylolpropane triacrylate (TMTA), a viscous liquid monomer at room temperature, to the perovskite precursor solution to provide grain boundary passivation and grain anchoring effects.…”

“…However, delamination of thick perovskite layers made by these methods is an issue. 38,51 It can be addressed by polymers as a buffer layer, 37,51,54 but the insulating polymer also suppresses the signal current. As discussed in the Scalability and Thickness Control section, more fundamental studies are needed to understand and address the delamination issue without reducing detectors' sensitivity.…”

“…Although various scalable processes have been proposed to fabricate perovskite films for direct X-ray detection, 37−56 there are only three reports, to the best of our knowledge, on the fabrication of Pe-FPDs due to additional challenges in the scalable processes such as uniformity and adhesion with TFT arrays. 37,38,44 In this perspective, we focus on the most recent and promising scalable processes for direct X-ray FPD applications. We first discuss the criteria for fabricating the perovskite layer based on the working mechanism of direct FPD.…”

“…The blade-coating method for fabrication of thick films has hitherto been limited to only MA-based perovskites as these can be dissolved in a high concentration to produce a viscous ink. [37][38][39]56 Sintering and Bonding. Sintering is a technique of making polycrystalline wafers by pressing precursor powders into a mold and heating it for solidification (Figure 4a).…”

Realizing Simultaneous X‐Ray Imaging and Dosimetry Using Phosphor‐Based Detectors with High Memory Stability and Convenient Readout Process

“…Although the performance at low integrated X-ray doses still needs to be improved for applications related to, e.g. medical imaging, [60][61][62][63][64][65] the high radiation resistance and large dose range allow using Ba 2 SiO 4 :Eu detectors for applications where high integrated doses and large dose ranges are encountered such as microbeam radiation therapy, food irradiation and detection of highly radioactively-contaminated areas. [45,53] Due to the variation of…”