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

Xiuwen Xu,Wei Qian,Jian Wang,Shihe Yang,Jianwei Chen,Jiecheng Yang,Shuang Xiao,Yongshuai Ge

doi:10.1002/advs.202102730

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.

Highlights

X-ray detection, but each with limitations stemming from its own intrinsic by a photodiode, the direct one is capaproperties
The 2D/3D double-layer perovskite film was prepared by successively depositing a 2D perovskite with a nominal composition of (PEA)2MA3Pb4I13 (thereafter denoted as (PEA)2MA3Pb4I13) and 3D perovskite MAPbI3 on a fluorine-doped SnO2 (FTO) glass using the ALS method,[17,18] and a full 3D film of MAPbI3 with a similar thickness was prepared as the control sample
It is found that in the control sample, the 60 μm thick MAPbI3 tend to preferentially and continuously crystallized along the direction perpendicular to the substrate (Figure 1c,e). Such a preferred vertical growth of the thick MAPbI3 film stems from its crystallization mechanism in the ALS process, which has been revealed in our recent work.[17]

Summary

Results and Discussion

The 2D/3D double-layer perovskite film was prepared by successively depositing a 2D perovskite with a nominal composition of (PEA)2MA3Pb4I13 (thereafter denoted as (PEA)2MA3Pb4I13) and 3D perovskite MAPbI3 on a fluorine-doped SnO2 (FTO) glass using the ALS method,[17,18] and a full 3D film of MAPbI3 with a similar thickness was prepared as the control sample. The continuous crystal growth along the vertical direction versus the grain boundary formation to accommodate strain along the horizontal direction results in the preferred vertical growth of the 3D perovskite.[17] Strikingly, in the double-layer perovskite, a welldefined layer-structured perovskite (thickness: 1.6 μm) oriented parallel to the substrate is clearly observed underneath the vertically grown MAPbI3 (Figure 1d,f), which is attributed to the 2D (PEA)2MA3Pb4I13 Such a layered structure is rather different from and unseen in the 2D perovskite films prepared by the one-shot spin-coating method,[19] which is expected to be beneficial for the suppression of ion migration.[20]. The gradient 2D perovskite has a layered structure with the low n and high n phases preferentially accumulated at the bottom and on the top, respectively, while the 3D MAPbI3 is crystallized with a preferred vertical orientation

From Double Layer Perovskite Films to Detector Design

X-Ray Detector Performance Assessment

Conclusion

Experimental Section

Data Availability Statement