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This paper investigates the optoelectronic properties of CsPbBr3, a lead-based perovskite, and Cs2AgBiBr6, a lead-free double perovskite, in composite thick films synthesized using mechanochemical and hot press methods, with poly(butyl methacrylate) as the matrix. Comprehensive characterization was conducted, including X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), UV–visible spectroscopy (UV–Vis), and photoluminescence (PL). Results indicate that the polymer matrix does not significantly impact the crystalline structure of the perovskites but has a direct impact on the grain size and surface area, enhancing the interfacial charge transfer of the composites. Optical characterization indicates minimal changes in bandgap energies across all different phases, with CsPbBr3 exhibiting higher photocurrent than Cs2AgBiBr6. This is attributed to the CsPbBr3 superior charge carrier mobility. Both composites showed photoconductive behavior, with Cs2AgBiBr6 also demonstrating higher-energy (X-ray) photon detection. These findings highlight the potential of both materials for advanced photodetector applications, with Cs2AgBiBr6 offering an environmentally Pb-free alternative. 

Hybrid perovskites have attracted great interest in solar energy conversion and optoelectronic applications. The interconnected ionic and electronic effects complicate assessing the underlying electrical processes while contributing greatly to the efficiency and stability of devices. Fortunately, these coupled processes manifest on distinct timescales that enable frequency-specific electrochemical analysis. However, hybrid perovskites dissolve in most of the common aqueous and organic solvents utilized for electrochemistry. Here, we utilize a hydrofluoroether (HFE) solvent toolkit to perform nondestructive electrochemical impedance spectroscopy of methylammonium lead iodide (MAPbI3) perovskite thin films. This enables the extraction of dielectric constants and double-layer formation in these perovskite films. 

A Reset MOSFET is added to a perovskite MOSFET-based photodetector to serve as a current source to mitigate the influence of ionic movement on the performance of the photodetector. With the added MOSFET, the hysteresis is significantly reduced, and the dark current is controllable. The on/off ratio resumes to 10^6 and an ultrasensitive responsivity (over 80,000 A/W) is achieved under only 13 nW/cm^2 red (665 nm) light intensity. 

Abstract Perovskites have emerged as a forerunner of electronics research due to their vast potential for optoelectronic applications. The numerous combinations of constituent ions and the potential for doping of perovskites lead to a high demand to track the underlying electronic properties. Solution‐based electrochemistry is particularly promising for detailed and facile assessment of perovskites. Here, electrochemical impedance spectroscopy (EIS) of methylammonium lead iodide (MAPbI₃) thin films is performed and model them with an equivalent circuit that accounts for solvent, ionic, and thin film effects. A dielectric constant consistent with prior AC studies and a diffusion constant harmonious with cation motion in MAPbI₃are extracted. An electrical double layer thickness in the perovskite film of 54 nm is obtained, consistent with lithium doping in perovskite films. Comparing the EIS and equivalent circuit model of perovskite films to control ITO‐only data enabled the assignment of the ions at each interface. This comparison implied a double layer of primarily lithium ions inside the perovskite film at the solution interface with significant recombination of ions on the solution side of the interface. This demonstrates EIS as a powerful tool for studying the fundamental charge accumulation and transport processes in perovskite thin films. 

Abstract Perovskite light‐emitting diodes (PeLEDs) are advancing because of their superior external quantum efficiencies (EQEs) and color purity. Still, additional work is needed for blue PeLEDs to achieve the same benchmarks as the other visible colors. This study demonstrates an extremely efficient blue PeLED with a 488 nm peak emission, a maximum luminance of 8600 cd m⁻², and a maximum EQE of 12.2% by incorporating the double‐sided ethane‐1,2‐diammonium bromide (EDBr₂) ligand salt along with the long‐chain ligand methylphenylammonium chloride (MeCl). The EDBr₂successfully improves the interaction between 2D perovskite layers by reducing the weak van der Waals interaction and creating a Dion–Jacobson (DJ) structure. Whereas the pristine sample (without EDBr₂) is inhibited by small stacking number (n) 2D phases with nonradiative recombination regions that diminish the PeLED performance, adding EDBr₂successfully enables better energy transfer from smallnphases to largernphases. As evidenced by photoluminescence (PL), scanning electron microscopy (SEM), and atomic force microscopy (AFM) characterization, EDBr₂improves the morphology by reduction of pinholes and passivation of defects, subsequently improving the efficiencies and operational lifetimes of quasi‐2D blue PeLEDs. 

A novel photodetecting device architecture that combines the optoelectronic property advantages of a perovskite and the amplification properties of a Si metal–oxide–semiconductor field‐effect transistor (MOSFET) to innovate a photodetecting system with ultrahigh sensitivity, especially in low‐light intensity, is demonstrated. This perovskite‐based MOSFET photodetector (PM‐PD) can respond as low as 116 nW cm⁻²with extremely high responsivity 4200 A W⁻¹. The perovskite is part of the gate dielectric to modulate the MOSFET drain current when the light intensity is changed. A direct bandgap, organic–inorganic hybrid halide perovskite with a large optical absorption coefficient, can enhance photodetector performance. However, perovskite materials are not good conductors for transporting photogenerated electrons and holes compared with single‐crystal silicon. Therefore, the perovskite was utilized as a dielectric where the capacitance is used instead. In the proposed PM‐PD architecture, changing the width‐to‐length (W/L) ratio of perovskite capacitor electrodes, can modulate the dark current from picoamperes to microamperes providing a tunable parameter for optimizing photodetecting performance. Furthermore, the capacitance of the perovskite can be modulated by frequency, which facilitates matching the capacitance of perovskite and MOSFET gate oxide—another important requirement for optimal photodetecting performance. Finally, our novel PM‐PD is commensurate with potential 3D monolithic integration. 

Abstract Blue electroluminescence is highly desired for emerging light‐emitting devices for display applications and optoelectronics in general. However, saturated, efficient, and stable blue emission has been challenging to achieve, particularly in mixed‐halide perovskites, where intrinsic ion motion and halide segregation compromises spectral purity. Here, CsPbBr_3−xCl_xperovskites, polyelectrolytes, and a salt additive are leveraged to demonstrate pure blue emission from single‐layer light‐emitting electrochemical cells (LECs). The electrolytes transport the ions from salt additives, enhancing charge injection and stabilizing the inherent perovskite emissive lattice for highly pure and sustained blue emission. Substituting Cl into CsPbBr₃tunes the perovskite luminescence from green through blue. Sky blue and saturated blue devices produce International Commission on Illumination coordinates of (0.105, 0.129) and (0.136, 0.068), respectively, with the latter meeting the US National Television Committee standard for the blue primary. Likewise, maximum luminances of 2900 and 1000 cd m⁻², external quantum efficiencies (EQEs) of 4.3% and 3.9%, and luminance half‐lives of 5.7 and 4.9 h are obtained for sky blue and saturated blue devices, respectively. Polymer and LiPF₆inclusion increases photoluminescence efficiency, suppresses halide segregation, induces thin‐film smoothness and uniformity, and reduces crystallite size. Overall, these devices show superior performance among blue perovskite light‐emitting diodes (PeLEDs) and general LECs.