A Microchannel‐Confined Crystallization Strategy Enables Blade Coating of Perovskite Single Crystal Arrays for Device Integration

Abstract

to millimeter scale, which is much larger than the carrier diffuse length in PSCs and thus greatly hinders their device applications. To solve this problem, a space-confined strategy was introduced into these methods to grow PSCs with thickness from several hundreds of nanometers to a few micrometers. [14,17−19] However, the lateral dimension of the resulting PSCs was limited by lack of solution supplement at the confined areas to provide enough solutes for continuous crystal growth. Moreover, the reported growth techniques for PSCs are quite time consuming and batch processes with limited throughput.Among various solution-based methods, blade coating has the advantages of high throughput, roll-to-roll compatibility, and minimal material wastage. [20−22] Although it has been widely applied to fabricate perovskite thin films for device applications, [23−26] PSCs deposited by the blade coating method generally exhibit a nonuniform morphology with low crystallinity, making them very challenging to fabricate high-performance integrated devices. The solution fluidic flow instabilities are believed to be the primary cause. [25,27] During the coating process, perovskite solutes would be turbulently transported to various locations of meniscus front, and this yields perovskite supersaturated phase containing randomly aggregated solutes, resulting in inhomogeneous nucleation and formation of the nonuniform and misaligned seed crystals. Therefore, it still remains a great challenge to achieve large-area growth of PSCs with highly uniform morphology via blade coating.Herein, we report the development, for the first time, of a microchannel-confined crystallization (MCC) strategy for the large-area growth of highly aligned PSCs with uniform morphology, which is applicable to device integration. The microchannels not only helped stabilize the transport of perovskite solutes but also reduced the density of nucleation events, ensuring the formation of uniform and continuous PSCs arrays in the channels. Both in situ experimental observation and theoretical simulation verified the vital roles of the microchannel in controlling the solution flow dynamics. The resulting PSCs possess a long carrier lifetime of 175 ns and an ultralow defect density of 2 × 10 9 cm −3 , which are comparable to the corresponding Perovskite single crystals (PSCs) possess superior optoelectronic properties compared to their corresponding polycrystalline films, but their applications of PSCs in high-performance, integrated devices are hindered by their heavy thickness and difficulty in scalable deposition. Here, a microchannel-confined crystallization (MCC) strategy to grow uniform and large-area PSC arrays for integrated device applications is reported. Benefiting from the confinement effect of the microchannels, solution flow dynamics is well controlled, and thus uniform deposition of PSC arrays with suitable thickness is achieved, meaning they are applicable for scale-up device applications. The resulting PSCs possess excellent optoelectronic proper...

Metal Halide Perovskites Functionalized by Patterning Technologies

“…[ 46 ] In addition to perovskite microplates, with the help of blade coating, aligned perovskite single‐crystal arrays can be self‐crystallized from perovskite precursor solution confined by microchannels. [ 13 ] In 2016, Wu's group demonstrated a novel approach to separate and fix the precursor solution into capillary bridges by using ordered micropillar arrays whose tops are hydrophilic and sidewalls are hydrophobic ( Figure a). [ 30 ] Therefore, as the evaporation of the solvents, patterned perovskite single‐crystal arrays were formed on the substrate.…”

“…Patterned template‐assisted crystallization of MHPs can create high‐quality nano/microcrystals with perfect surface and homogeneous crystal size. The patterned templates are usually composed of silicon, [ 27,30–33 ] silicon oxide, [ 34 ] alumina, [ 21,35–37 ] 2D materials, [ 38–40 ] and polymer [ 13,26,41–49 ] by the means of photolithography, direct laser writing, focused‐ion‐beam etching, or electron‐beam etching. The perovskite precursor solution is usually dropped on the hydrophilic substrates and confined by hydrophobic patterned molds to create crystal seeds and grow ordered crystal arrays.…”

“…fabricated MAPbI 3 perovskite single‐crystalline arrays by microchannel‐assisted crystallization, showing a long carrier lifetime (175 ns) and an ultralow defect density (2 × 10 9 cm −3 ). [ 13 ] They employed a vertical‐type structure to construct photodetector devices, enabling the strategy of the photodetection circuitry for image sensors as shown in Figure 7c.…”

“…Reproduced with permission. [ 13 ] Copyright 2020, Wiley‐VCH. d) Illustration of the CsPbBr 3 single‐crystal photodetector array and e) corresponding I – V curves under different incident light power densities.…”

“…[ 7–9 ] In addition to the prosperity in photovoltaic and light‐emitting devices, tremendous efforts are carried on the MHPs pursuing ultra‐low threshold laser, [ 10,11 ] and ultra‐sensitive photo‐ and X‐ray detectors. [ 12–14 ] Solution processing method is commonly used for fabricating perovskite thin films. This cost‐effective method allows large‐scale production of smooth and uniform perovskite thin films served as the active layers of solar cells.…”