Bendable 3D-structured x-ray photodetectors based on pure PbI2 single crystal
PbI2 crystal is a typical layered material with a I–Pb–I monolayer as a repeating unit. Benefiting from the coexistence of ionic and van der Waals bonding, the crystal exhibits low hardness and a low Young’s modulus, slips easily along the a–b plane, and is endowed with inherently high flexibility. In this work, bendable three-dimensional (3D)-structured x-ray photodetectors based on PbI2 crystal were prepared, and finite element simulation was employed to reveal the von Mises stress distribution from the surface to the bulk of the crystal, indicating the bending stress associated with the crystal’s thickness. The uniformly distributed electric bias field inside the crystal constrains the carrier transport process, provides a consistent geometric variation and electrical contact between the crystal and the electrodes, and further ensures a high effective collection area and enhanced collection capacity for photocarriers, even when the device is subjected to bending. The degradation percentage of the sensitivity after 100 bending cycles is 12.7% and 6.6% for thick (100 μm) and thin (10 μm) samples, respectively. All the simulated and experimental results indicate that PbI2 crystal, when used to construct a 3D-structured device of appropriate thickness, is a promising candidate for the development of flexible x-ray photodetectors.