Solution‐Processed High‐Quality Cesium Lead Bromine Perovskite Photodetectors with High Detectivity for Application in Visible Light Communication

Abstract

devices in VLC are essential because their response speed, detectivity (D*), and stability determine the quality and speed of the signal acceptance. All-inorganic perovskites are very attractive for their application in the PDs with requirements of high durability, wide-range spectral responses, ultra-high D*, and fast response speed, due to their merits of high thermal stability, tunable bandgaps, high light absorption coefficients, and long carrier diffusion lengths. [2][3][4][5] Particularly, cesium lead bromide (CsPbBr 3 ), a prototypical all-inorganic perovskite with a bandgap energy of 2.4 eV, has been widely used for fabricating solar cells and PDs. [6] The preparation of high-quality CsPbBr 3 films with a large lateral area is crucial for their commercialization. Luchkin et al. fabricated inorganic CsPbBr 3 perovskite solar cells with the best efficiency of 3.9% by using a vacuum deposition process. The poor efficiency was attributed to the off-stoichiometric ratios of the vacuum-processed precursors. [7] Recently, inorganic perovskite quantum dots (QDs) were developed to fabricate perovskite photoelectronic devices, demonstrating decent device performance. [8,9] However, these perovskite films consisted of mosaic QDs capped with a large amount of organic ligands and surface traps, which hinder the carrier transport and limit the device performance. Solutionprocessed CsPbBr 3 polycrystalline (PC) films are an attractive alternative due to better process controllability, endowing them with great potential for large-scale commercial fabrication of perovskite photoelectronic devices. [10][11][12][13] Unfortunately, the fabrication of high-quality CsPbBr 3 PC films via solution processes is challenging. The low solubility of CsBr in dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) solvents causes insufficient and unbalanced reaction of the precursors, which leads to discontinuous and porous morphology and off-stoichiometric compositions in solution-processed perovskite films. [14,15] Additionally, due to the much lower solubility of CsBr than that of PbBr 2 in the solvents, CsBr behaves as the growth seeds during the nucleation of perovskite crystallites, which aggravates the formation of voids and impurity phases, hindering the achievement of the high-performance PDs. [16] Cesium lead bromide (CsPbBr 3 ) perovskite photodetectors (PDs) are attractive for applications in visible light communication (VLC) due to ultra-high detectivity and fast response speed. However, the fabrication of high-quality CsPbBr 3 polycrystalline films using solution-based process is very challenging. Due to the low solubility of CsBr in precursor solutions, solution-processed CsPbBr 3 films are typically discontinuous and porous, hindering the performance of resulting PDs. Herein, a facile and modified sequential spin-coating method is introduced to prepare high-crystallinity, pinhole-free CsPb 2 Br 5 -CsPbBr 3 perovskite films with an average grain size of ≈1 µm. The hole-transport-layer-free (HTL-free) PDs based on the CsPb ...

Low‐Dimensional Metal Halide Perovskite Photodetectors

“…To investigate the potential of MHP PDs to the OWC, some groups simulated the core optocoupler of an OWC system, which consists of a signal generator, driving a light source (e.g., LED) to turn on and off quickly and an MHP PD connecting to a rapid oscilloscope, as shown in Figure 14a. [120,[309][310][311][312] Gao's group first integrated MHP PDs into an OWC system as an optical signal receiver on transmitting text and audio signals. [309] Li et al demonstrated MAPbI 3 PDs applied in a VLC system.…”

Low‐Dimensional‐Networked Cesium Lead Halide Perovskites: Properties, Fabrication, and Applications

“…Nevertheless, the low solubility of CsX in precursor solution gave rise to discontinuous and porous films, hindering the final product. [ 122 ] In the preparation of bulk film, trace impurities were a common problem, which necessitate more research efforts in the future.…”

“…[ 197 ] Benefiting from the deposition method, the compositions and thickness of the films could be precisely controlled by varying the CsBr/PbBr 2 ratio and dosage. Recently, a solution deposition coating [ 122 ] and a post‐treatment method [ 198 ] have been developed in the synthesis of CsPbBr 3 /CsPb 2 Br 5 composite films. In these films, the presence of wide bandgap semiconductor CsPb 2 Br 5 provided significant self‐passivation at the interface, which was believed to have reduced the charge recombination in CsPbBr 3 .…”

“…When a rational modification was employed during the synthesis and device construction, the performance was further enhanced in CsPbBr 3 /CsPb 2 Br 5 ‐based photodetectors, now exhibiting a fast response of 0.006 and 0.064 ms for rising and decay time, respectively. [ 122 ] In addition to CsPbBr 3 /CsPb 2 Br 5 , dual‐phase CsPbBr 3 /Cs 4 PbBr 6 films were employed in photodetectors for the deep‐UV light region (200–350 nm). [ 173 ] It exhibited a response time as fast as 0.008/0.034 ms and a high responsivity of 49.4 mA W −1 at 254 nm.…”

Lead‐Free Halide Double Perovskite Nanocrystals for Light‐Emitting Applications: Strategies for Boosting Efficiency and Stability

“…In recent years, lead halide perovskite nanocrystals, APbX 3 (A = CH 3 NH 3 + (MA + ), NH 2 HCNH 2 + (FA + ), and Cs + , X = Cl, Br, and I) have attracted great interest and been widely used in solar cells, [ 1,2 ] lasers, [ 3,4 ] light‐emitting diodes (LEDs), [ 5,6 ] bioimaging [ 7 ] and photodetectors [ 8,9 ] due to their broad excitation, narrow‐band emission (full width at half‐maximum (FWHM) of 12–42 nm), [ 10,11 ] tunable wavelength (400–700 nm), [ 12‐14 ] high photoluminescence quantum yield ( PLQY ≈ 100%), [ 15,16 ] direct bandgap, [ 17 ] defect tolerance, [ 18 ] long diffusion length, [ 19,20 ] high carrier mobility, [ 21 ] and long carrier lifetime. [ 22,23 ] Especially, lead halide perovskite nanocrystals are suitable for solid‐state lighting and high‐definition display applications due to their wide color gamut ( NTSC ≈ 140%), [ 24,25 ] high color purity, [ 26 ] as well as facile synthesis methods.…”