Sequential Growth of 2D/3D Double‐Layer Perovskite Films with Superior X‐Ray Detection Performance

Abstract

Perovskite materials in different dimensions show great potential in direct X‐ray detection, but each with limitations stemming from its own intrinsic properties. Particularly, the sensitivity of two‐dimensional (2D) perovskites is limited by poor carrier transport while ion migration in three‐dimensional (3D) perovskites causes the baseline drifting problem. To circumvent these limitations, herein a double‐layer perovskite film is developed with properly aligned energy level, where 2D (PEA)2MA3Pb4I13 (PEA=2‐phenylethylammonium, MA=methylammonium) is cascaded with vertically crystallized 3D MAPbI3. In this new design paradigm, the 3D layer ensures fast carrier transport while the 2D layer mitigates ion migration, thus offering a high sensitivity and a greatly stabilized baseline. Besides, the 2D layer increases the film resistivity and enlarges the energy barrier for hole injection without compromising carrier extraction. Consequently, the double‐layer perovskite detector delivers a high sensitivity (1.95 × 104 μC Gyair−1 cm−2) and a low detection limit (480 nGyair s−1). Also demonstrated is the X‐ray imaging capacity using a circuit board as the object. This work opens up a new avenue for enhancing X‐ray detection performance via cascade assembly of various perovskites with complementary properties.

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

“…(i) Cross-sectional SEM image and (j) schematic illustration of the 2D/3D double-layer perovskite films obtained via the ALS method. Reprinted with permission from ref , which is licensed under a Creative Commons Attribution NonCommercial License 4.0 ().…”

“…Yang’s group has developed a similar strategy named the aerosol–liquid–solid (ALS) method, ,,, where an aerosol of the precursor solution is transported and deposited onto the substrate. By continuous aerosol supply, the liquid–solid interface is formed on the surface of the film, and the bottom-up growth is realized (Figure h).…”

“…Additionally, they addressed the significant issue of suppressing dark current by fabricating the heterojunction structure realized through sequential growth of 2D/3D double-layer perovskites (Figure 8j). 55 As mentioned above, the spray-coating method is promising for Pe-FPD applications, as uniform, thick, and large-area films can be formed at low temperatures, enabling direct deposition of the perovskite layer on TFT arrays. In addition, a unique columnar structure will contribute to a high spatial resolution and a high sensitivity because the grain boundaries may suppress the charge diffusion in the lateral direction but not in the vertical direction.…”

“…Considering the difficulty of upscaling single crystals to the required area of at least 100 cm 2 , a scalable deposition process for polycrystalline perovskite films is required. Although various scalable processes have been proposed to fabricate perovskite films for direct X-ray detection, − 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. ,, …”

Searching for High-Quality Halide Perovskite Single Crystals toward X-ray Detection

“…Previous work for polycrystalline films may provide shortcuts for surface treatments of single crystals (Figure a). Many effective post-treatment strategies have been developed, such as UV-O 3 , replenishing with organic salt, and 2D/3D perovskite heterojunction growth. , It is crucial to develop standard protocols for postprocessing perovskite single crystals in the near future.…”