Surface Engineering of All‐Inorganic Perovskite Quantum Dots with Quasi Core−Shell Technique for High‐Performance Photodetectors

Abstract

All‐inorganic lead halide perovskites with good surface morphology show substantial prospect for optoelectronic devices. However, the anion exchange of coordinated alkylamine ligands (e.g., oleic acid and oleylamine) can detach ligands and induce more interface trap sites, subsequently to reduce device performance. In this paper, therefore, a simple solution‐processed route is presented to synthesize quasi coreshell CsPbBr3formamidinium iodide (FAI = CH(NH2)2I) colloidal quantum dots (CQDs), and then it is applied as the active layer for photodetectors by finely controlling the ligands exchange. The presence of FAI = CH(NH2)2I on CsPbBr3 is confirmed by Fourier transform infrared spectroscopy. As a result, the photodetector ITO/ZnO (100 nm)/CsPbBr3 (150 nm)/Au show an enhanced specific detectivity over 1013 Jones with a responsivity of 19 A W1 under 3 mW cm2 405 nm illumination at 1.5 V. The experimental data show that the enhanced device performance is due to the improved crystallinity and less surface defects of CsPbBr3 CQDs, as the result of less alkylamine ligands is detached during its FAI passivation, thus the charge carriers' mobility of the film is improved. Therefore, it provides a promising way for high‐performance solution‐processed all‐inorganic CsPbBr3 based optoelectronic devices.

Surface Chemistry Engineering of Perovskite Quantum Dots: Strategies, Applications, and Perspectives

“…Similarly, a low concentration (1–2 mg mL –1 ) of FAI salt was added in the CsPbBr 3 QD inks to form a quasi‐core–shell heterostructure, which can effectively eliminate sub‐gap trap‐states at surface of PQDs and thus lead to a high responsivity of 19 A W –1 with a specific detectivity of 1.7 × 10 13 Jones in the corresponding vertical photoconductors. [ 145 ] Besides, stacking with organic semiconductors featuring Lewis acid or base nature can passivate the positively or negatively charged defects at the interface of PQD films, respectively. Simultaneously, these p‐type organic passivation interfacial layers such as P3HT, [ 146 ] poly(4‐butyl‐ N , N ‐bisphenyl‐benzidine) (poly‐TPD), [ 147,148 ] and dinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]thiophene [ 26 ] can form n‐p Schottky heterojunctions with PQDs, in which an interfacial band bend allows efficient hole extraction while blocking electrons.…”

Core/Shell Metal Halide Perovskite Nanocrystals for Optoelectronic Applications

“…Large absorption coefficients, higher carrier mobility, long carrier diffusion length, and long carrier lifetime [167][168][169][170] indicate tremendous prospects of perovskite NCs for applications in photodetectors. Recently, high-performance photodetectors with a layer of quasi-core/shell CsPbBr 3 /FAI NCs were reported, [170] where the FAI salt was used to facilitate charge transfer from the core to the shell resulting in enhanced light absorption. [171] Besides, the modified inter-NCs dielectric environment as well as the surface defect passivation of NCs can also facilitate the carrier extraction and transfer in perovskite NC films.…”

Lanthanide-doped inorganic halide perovskites (CsPbX3): novel properties and emerging applications

“…5,6 Because of the direct bandgap, high absorption coefficient, high mobility, long carrier lifetime, costeffectiveness, etc., the all-inorganic cesium-lead halide perovskites (CsPbX 3 , where X = Cl, Br, and I) have been considered as rising stars for photovoltaic applications. [7][8][9][10][11] They are also used in making colored and white LEDs, [12][13][14][15] fluorescence sensors, 16 oxygen detection sensors, 17 gas sensors, 18 humidity sensors, 19 field-effect transistors, 20,21 filter-free color image sensors, 22 display applications, 23 photodetectors, [24][25][26] spectro-chemical probes, explosive detectors, 27 laser fabrication, 28 X-ray detection, 29,30 etc. In this review, we mainly discuss the basics of halide perovskites, including the major advantages and challenges of halide perovskites.…”