Solution-phase, template-free synthesis of PbI2 and MAPbI3 nano/microtubes for high-sensitivity photodetectors

Exploring Nanoscale Perovskite Materials for Next-Generation Photodetectors: A Comprehensive Review and Future Directions

The rapid advancement of nanotechnology has sparked much interest in applying nanoscale perovskite materials for photodetection applications. These materials are promising candidates for next-generation photodetectors (PDs) due to their unique optoelectronic properties and flexible synthesis routes. This review explores the approaches used in the development and use of optoelectronic devices made of different nanoscale perovskite architectures, including quantum dots, nanosheets, nanorods, nanowires, and nanocrystals. Through a thorough analysis of recent literature, the review also addresses common issues like the mechanisms underlying the degradation of perovskite PDs and offers perspectives on potential solutions to improve stability and scalability that impede widespread implementation. In addition, it highlights that photodetection encompasses the detection of light fields in dimensions other than light intensity and suggests potential avenues for future research to overcome these obstacles and fully realize the potential of nanoscale perovskite materials in state-of-the-art photodetection systems. This review provides a comprehensive overview of nanoscale perovskite PDs and guides future research efforts towards improved performance and wider applicability, making it a valuable resource for researchers.

Ultrasensitive alkaline phosphatase activity assay based on controllable signal probe production coupled with the cathodic photoelectrochemical analysis

A highly sensitive and selective split-type perovskite-based photoelectrochemical (PEC) platform was developed for measuring alkaline phosphatase (ALP) activity in milk and serum samples. ALP in the test sample hydrolyzed 2-phosphate sesquimagnesium salt hydrate (AAPS) in a 96-microwell plate to produce ascorbic acid (AA), a PEC electron donor. The resulting AA, which could preferentially annihilate the photogenerated holes, indirectly reflects ALP activity. The PEC used a cetyltrimethylammonium bromide (CTAB)-functionalized CH₃NH₃PbI₃ (CTAB@CH₃NH₃PbI₃) film as the cathode to monitor the controlled AA production. Due to the excellent photoelectric characteristics of the CH₃NH₃PbI₃ perovskite and the split-type assay, excellent sensitivity and selectivity for ALP detection were obtained. Under the optimum experimental conditions, ALP activity with a limit of detection (LOD) of 2.6 × 10^-4 U/L in a linear dynamic range of 10^-3 ∼ 10² U/L was obtained. With its sensitive, rapid, and high-throughput detection capabilities, this split-type and label-free PEC platform has great potential for use in food and biomedical analysis.

Recent progress in layered metal halide perovskites for solar cells, photodetectors, and field-effect transistors

Metal halide perovskite materials demonstrate immense potential for photovoltaic and electronic applications. In particular, two-dimensional (2D) layered metal halide perovskites have advantages over their 3D counterparts in optoelectronic applications due to their outstanding stability, structural flexibility with a tunable bandgap, and electronic confinement effect. This review article first analyzes the crystallography of different 2D perovskite phases [the Ruddlesden-Popper (RP) phase, the Dion-Jacobson (DJ) phase, and the alternating cations in the interlayer space (ACI) phase] at the molecular level and compares their common electronic properties, such as out-of-plane conductivity, crucial to vertical devices. This paper then critically reviews the recent development of optoelectronic devices, namely solar cells, photodetectors and field effect transistors, based on layered 2D perovskite materials and points out their limitations and potential compared to their 3D counterparts. It also identifies the important application-specific future research directions for different optoelectronic devices providing a comprehensive view guiding new research directions in this field.

Environmentally Friendly Syntheses of Self-Healed and Printable CsPbBr3 Nanocrystals

Generally, solvents used to synthesize perovskite NCs are toxic, which leads to waste liquid pollution and environmental degradation. Herein, we developed a novel environmentally friendly polar solvent method to synthesize CsPbBr₃ nanocrystals (NCs). Over 65% photoluminescence quantum yield (PLQYs) for NCs could be maintained over 45-850 h of storage time, and a maximum was 78% at 750 h. Such amazing stability in polar solvents is dominated by a ripening process, which heals surface defects. Additionally, their solid films also exhibited good moisture stability. Furthermore, CsPbBr₃ NCs were applied to inkjet-printing to prepare high-quality patterned films.

Plasmonic and Graphene-Functionalized High-Performance Broadband Quasi-Two-Dimensional Perovskite Hybrid Photodetectors

Quasi-two-dimensional (2D) layered organic-inorganic hybrid perovskites have attracted extensive attention, owing to their excellent optoelectronic tunability and moisture stability compared with three-dimensional perovskite counterparts and show great potential for application in photodetectors (PDs). However, owing to the unavoidable grain boundary defects of perovskite polycrystalline films, the photocurrent is limited by poor light absorption and charge mobility. Therefore, the preparation of quasi-2D perovskite films with strong light trapping and high charge mobility has been challenging. In this study, novel broadband quasi-2D perovskite (BA)₂(FA)_n-1Pb_nI_3n+1 hybrid-structure PDs with good stability were fabricated by combining both monolayer graphene and Au square nanoarrays. The hybrid system using both graphene and Au square nanoarrays effectively improved the carrier mobility and light absorption and simultaneously maximized light trapping and light-induced carrier extraction, which resulted in PDs with greatly enhanced photocurrent in the visible and near-infrared range. The graphene-Au array-perovskite-based PDs had a low dark current of 10^-10 A, large on/off ratio of 10⁴, high responsivity of 18.71 A W^-1, and detectivity of 2.21 × 10¹³ Jones. The responsivity and detectivity were two orders of magnitude higher than those of PDs based only on perovskites. This work demonstrates a promising and feasible device based on the coupling of a gold array, layered graphene, and quasi-2D perovskites, which shows great potential for the development of high-performance broadband perovskite PDs.

Carrier Diffusion and Recombination Anisotropy in the MAPbI3 Single Crystal

MAPbI₃, one of the archetypical metal halide perovskites, is an exciting semiconductor for a variety of optoelectronic applications. The photoexcited charge-carrier diffusion and recombination are important metrics in optoelectronic devices. Defects in grain interiors and boundaries of MAPbI₃ films cause significant nonradiative recombination energy losses. Besides defect impact, carrier diffusion and recombination anisotropy introduced by structural and electronic discrepancies related to the crystal orientation are vital topics. Here, large-sized MAPbI₃ single crystals (SCs) were grown, with the (110), (112), (100), and (001) crystal planes simultaneously exposed through the adjusting ratios of PbI₂ to methylammonium iodide (MAI). Such MAPbI₃ SCs exhibit a weak n-type semiconductor character, and the Fermi levels of these planes were slightly different, causing a homophylic p-n junction at crystal ledges. Utilizing MAPbI₃ SCs, the photoexcited carrier diffusion and recombination within the crystal planes and around the crystal ledges were investigated through time-resolved fluorescence microscope. It is revealed that both the (110) and (001) planes were facilitated to be exposed with more MAI in the growth solutions, and the photoluminescence (PL) of these planes manifesting a red-shift, longer carrier lifetime, and diffusion length compared with the (100) and (112) planes. A longer carrier diffusion length promoted photorecycling. However, excessive MAI-assisted grown MAPbI₃ SCs could increase the radiative recombination. In addition, it revealed that the carrier excited within the (001) and (112) planes was inclined to diffuse toward each other and was favorable to be extracted out of the grain boundaries or crystal ledges.

Fabrication of graphene: CdSe quantum dots/CdS nanorod heterojunction photodetector and role of graphene to enhance the photoresponsive characteristics

Integration of graphene with semiconducting quantum dots (QDs) provides an elegant way to access the intrinsic properties of graphene and optical properties of QDs concurrently to realize the high-performance optoelectronic devices. In the current article, we have demonstrated the high-performance photodetector based on graphene: CdSe QDs/CdS nanorod heterostructures. The resulting heterojunction photodetector with device configuration ITO/graphene: CdSe/CdS nanorods/Ag show excellent operating characteristics including a maximum photoresponsivity of 15.95 AW^-1and specific detectivity of 6.85 × 10¹²Jones under 530 nm light illumination. The device exhibits a photoresponse rise time of 545 ms and a decay time of 539 ms. Furthermore, the study of the effect of graphene nanosheets on the performance enhancement of heterojunction photodetector is carried out. The results indicate that, due to the enhanced energy transfer from photoexcited QDs to graphene layer, light absorption is increased and excitons are generated led to the enhancement of photocurrent density. In addition to that, the graphene: CdSe QDs/CdS nanorod interface can facilitate charge carrier transport effectively. This work provides a promising approach to develop high-performance visible-light photodetectors and utilizing advantageous features of graphene in optoelectronic devices.

NiOx nanoparticles obtained from hydrothermally treated NiC2O4 as an electron blocking layer for organic photodetectors

A room-temperature p-type NiO_x film synthesized from a NiC₂O₄ precursor via hydrothermal treatment is employed as an electron blocking layer (EBL) to fabricate organic photodetectors (OPDs). A simple and efficient calcine process at 375 °C in air decomposes the NiC₂O₄ particles into NiO_x, removes organic components and crystal water, and releases CO₂ gas. Our experimental results indicate that this gaseous by-product prevents the agglomeration of NiO_x, which yields smaller nanoparticles (5-10 nm). The formation of an EBL at room temperature improves device performance. After optimization, the performance parameters obtained, including dark current density, responsivity, specific detectivity and response, are 1.13 × 10^-7 A cm^-2, 0.74 A W^-1, 3.86 × 10¹² Jones, and 0.5/8 ms, respectively. Additionally, the dark current is reduced by more than an order of magnitude after the insertion of the NiO_x layer. The proposed simple and easy method for producing an EBL could be beneficial for the commercial low-temperature and large-area preparation of OPDs.

Study of Metal-Semiconductor-Metal CH3NH3PbBr3 Perovskite Photodetectors Prepared by Inverse Temperature Crystallization Method

Numerous studies have addressed the use of perovskite materials for fabricating a wide range of optoelectronic devices. This study employs the deposition of an electron transport layer of C₆₀ and an Ag electrode on CH₃NH₃PbBr₃ perovskite crystals to complete a photodetector structure, which exhibits a metal–semiconductor–metal (MSM) type structure. First, CH₃NH₃PbBr₃ perovskite crystals were grown by inverse temperature crystallization (ITC) in a pre-heated circulator oven. This oven was able to supply uniform heat for facilitating the growth of high-quality and large-area crystals. Second, the different growth temperatures for CH₃NH₃PbBr₃ perovskite crystals were investigated. The electrical, optical, and morphological characteristics of the perovskite crystals were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible spectroscopy, and photoluminescence (PL). Finally, the CH₃NH₃PbBr₃ perovskite crystals were observed to form a contact with the Ag/C₆₀ as the photodetector, which revealed a responsivity of 24.5 A/W.