Stable α‐CsPbI₃ Perovskite Nanowire Arrays with Preferential Crystallographic Orientation for Highly Sensitive Photodetectors

Abstract

All-inorganic metal-halide perovskites CsPbX 3 (X = Cl, Br, I) exhibit higher stability than their organic-inorganic hybrid counterparts, but the thermodynamically instable perovskite α phase at room temperature of CsPbI 3 restricts the practical optoelectronic applications. Although the stabilization of α-CsPbI 3 polycrystalline thin films is extensively studied, the creation of highly crystalline micro/nanostructures of α-CsPbI 3 with large grain size and suppressed grain boundary remains challenging, which impedes the implementations of α-CsPbI 3 for lateral devices, such as photoconductor-type photodetectors. In this work, stable α-CsPbI 3 perovskite nanowire arrays are demonstrated with large grain size, high crystallinity, regulated alignment, and position by controlling the dewetting dynamics of precursor solution on an asymmetric-wettability topographical template. The correlation between the higher photoluminescence (PL) intensity and longer PL lifetime indicates the nanowires exhibit stable α phase and suppressed trap density. The preferential (100) orientation is characterized by discrete diffraction spots in grazing incidence wide-angle scattering patterns, suggesting the long-range crystallographic order of these nanowires. Based on these high-quality nanowire arrays, highly sensitive photodetectors are realized with a responsivity of 1294 A W −1 and long-term stability with 90% performance retention after 30-day ambient storage.

Flexible and Self‐Powered Lateral Photodetector Based on Inorganic Perovskite CsPbI3–CsPbBr3 Heterojunction Nanowire Array

“…Previous studies reported that the PVP molecule can stabilize the CsPbI 3 crystal by interacting with the Cs + to change its surface energy state, and a 10% weight ratio yields the optimized results. [ 8,10 ] So we add 10 wt% PVP into the precursor solvent. A vacuum treatment process is necessary before the annealing (Figure S1c, Supporting Information), or the patterned CsPbI 3 will not transfer into the black phase but the yellow phase instead (Figure S2, Supporting Information).…”

“…According to the previous report, the disordered crystallographic growth will contribute to the intensity of (110) plane, so its reduction means a more preferential crystal growth along the desired (100) crystallographic orientation, suggesting the improvement of the film quality. [ 10 ] A control flat film at the 0.6 m concentration is fabricated for comparison. SEM images (Figure S4, Supporting Information) show that the flat film has rough morphology with many grain boundaries, while the nanowire array does not show obvious boundaries.…”

“…Inorganic perovskites possess strong light absorption, high carrier mobility, and good stability, and have been widely explored in many fields such as solar cells and photodetectors. [ 1–13 ] Specifically, self‐powered perovskite photodetector can work without external energy source, depending on a built‐in electric field which can separate the light‐induced carrier. [ 14–16 ] The most studied device type is the vertical heterojunction.…”

“…[ 1,29–33 ] Particularly, a high‐quality inorganic CsPbI 3 nanowire array owns few undesired grain boundaries, and the unique 1D geometry makes it more tolerate to interfacial strain caused by the crystal lattice mismatch across the junction, which makes it a good candidate for the lateral heterojunction device. [ 10 ] Ion exchange strategy is widely applied in fabricating heterojunction on a single nanowire. For example, Yang et al combined anion exchange and nanofabrication technique to obtain CsPbBr 3 –CsPbCl 3 heterojunction from the CsPbBr 3 wire.…”

Controllable Growth of High‐Quality Inorganic Perovskite Microplate Arrays for Functional Optoelectronics

“…[ 20,21 ] Random nucleation is a disadvantage in the precise control of crystal locations for device integration. [ 22,23 ] Hence, the controllable growth of high‐quality perovskite single crystals for a device is highly challenging. This significantly hinders the controllable production of high‐performance perovskite single‐crystal devices in arrays for integrated electronic and optoelectronic systems.…”