Perovskite Optoelectronic Devices Research Articles

First-principles calculations of the effect of vacancy defects on the optoelectronic and mechanical properties of the double perovskite Cs2NaInCl6

Abstract Cs2NaInCl6 have become a hot research topic in perovskite optoelectronic materials. However, there is no research on the vacancy properties of Cs2NaInCl6 at present. Herein，using density functional theory-based first-principles calculations, the impact of Cs, Na, In, and Cl single vacancies on the microstructure, electronic, optical, and mechanical properties of the double perovskite Cs2NaInCl6 were investigated. The research shows that the presence of vacancy defects leads to distortion of the Cs2NaInCl6 double perovskite structure and an increase in the unit cell volume. Cs vacancy (VCs) and Na vacancy (VNa) cause an increased band gap for Cs2NaInCl6, by 2.92eV and 3.1eV respectively, without changing the characteristics of the initial direct band gap; VIn and VCl cause the intrinsic semiconductor Cs2NaInCl6 to transform into p-type and n-type semiconductors, respectively, altering the conductivity of Cs2NaInCl6. In terms of optical properties, different vacancy defect systems exhibit different absorption abilities in the visible and ultraviolet light ranges. The defect system overall improves light absorption in the low energy region, and as the incident photon energy increases, the material exhibits the best optical performance at around 15eV. In addition, it is found that VCs, VNa, and VIn caused blue shift in the absorption edge of Cs2NaInCl6, while VCl caused red shift in the absorption edge. In terms of mechanical properties, defects cause varying degrees of reduction in Young's modulus (E), shear modulus (G), and bulk modulus (B) of Cs2NaInCl6, which to some extent alters the mechanical properties of Cs2NaInCl6. These research results provide theoretical guidance for understanding the influence of vacancies on the properties of Cs2NaInCl6 double perovskite and optimizing the performance of perovskite optoelectronic devices, and they also enhance its applications in photovoltaic cells, optoelectronic sensors, and other optoelectronic coupling devices.

Enhancing negative thermal quenching in green-emitting perovskite microspheres via shallow trap state modulation

AbstractFor luminescent materials, negative thermal quenching (NTQ), characterized by an increase in the luminescent intensity with temperature, has a large potential in lighting and display technologies. However, leveraging NTQ in metal halide perovskites is challenging, and the mechanism is not well understood. Herein, by utilizing low-temperature photoluminescence, persistent luminescence and thermoluminescence, the origins of NTQ in CsPbBr3 microspheres are systematically studied, which pertain to the liberation of carriers from shallow trap states. Experimental and theoretical investigations reveal that the energy of these shallow defect states is approximately 0.135 eV beneath the conduction band. A rapid thermal treatment increases the density of these shallow traps and amplifies the NTQ effect, resulting in an enhancement of room-temperature photoluminescence by more than 60% compared to that at 150 K. The process also reduces the threshold for amplified spontaneous emission to about 45 W/cm2. Our findings not only provide a deeper understanding of the NTQ phenomenon in CsPbBr3 microspheres but also open new avenues for enhancing the performance of perovskite optoelectronic devices through energy state regulation.

Managing Edge States in Reduced-Dimensional Perovskites for Highly Efficient Deep-Blue LEDs.

Pure-halide reduced-dimensional perovskites, featuring large exciton binding energy and tunable bandgap, show great potential for high-efficiency deep-blue perovskite light-emitting diodes (PeLEDs). However, their efficiency, particularly in the low n-value phase domain ("n" represents the number of octahedral sheets), lags behind analogous perovskite emitters. Herein, it is demonstrated that the vibration of edge-dangling octahedra in the low n-value phase activates notorious exciton-phonon (EP) coupling, thereby deteriorating efficiency. To address this issue, an approach is reported to manage edge-state lattices by introducing tris(4-fluorophenyl) phosphine (TFP) ligands. Attributed to the large steric hindrance of TFP ligands and their strong binding affinity for edge-dangling octahedra, the edged-octahedral tilting reconstruction can effectively suppress lattice vibration and inhibit EP coupling. This strategy yields deep-blue emitting film with a spectral linewidth of 21nm and a photoluminescence quantum yield of 85% at low excitation densities. The resulting PeLEDs achieve deep-blue emission at 469nm, with a maximum luminance of 2,428cdm-2 and a maximum external quantum efficiency of 10.4%, marking them among the most efficient deep-blue PeLEDs reported. The strategy also showcases universality for higher n-value reduced-dimensional perovskites. It is believed that the observation, along with the edge-state management strategy, lays the groundwork for further advancements in reduced-dimensional perovskite optoelectronic devices.

Micrometer-Resolution Fluorescence and Lifetime Mappings of CsPbBr3 Nanocrystal Films Coupled with a TiO2 Grating.

Enhancing light emission from perovskite nanocrystal (NC) films is essential in light-emitting devices, as their conventional stacks often restrict the escape of emitted light. This work addresses this challenge by employing a TiO2 grating to enhance light extraction and shape the emission of CsPbBr3 nanocrystal films. Angle-resolved photoluminescence (PL) demonstrated a 10-fold increase in emission intensity by coupling the Bloch resonances of the grating with the spontaneous emission of the perovskite NCs. Fluorescence lifetime imaging microscopy (FLIM) provided micrometer-resolution mapping of both PL intensity and lifetime across a large area, revealing a decrease in PL lifetime from 8.2 ns for NC films on glass to 6.1 ns on the TiO2 grating. Back focal plane (BFP) spectroscopy confirmed how the Bloch resonances transformed the unpolarized, spatially incoherent emission of NCs into polarized and directed light. These findings provide further insights into the interactions between dielectric nanostructures and perovskite NC films, offering possible pathways for designing better performing perovskite optoelectronic devices.

2D layered halide perovskite for field-effect transistors

Field-effect transistors are crucial components for modern electronics, generating significant research and profitable interest. Metal halide perovskites have recently emerged as a pioneering active material in solar cells, generating interest in their potential use in other electronic and (opto)electronic devices, including field-effect transistors and phototransistors. However, before they can be commercialized, they still face significant challenges owing to their immanent instabilities with respect to heat, moisture, and light. In contrast, due to their exceptional environmental stability, the newly emerging two-dimensional Ruddlesden–Popper type perovskites have garnered significant recognition. The current state of the field is covered in this review article, as are the problems, and a perspective for the scenarios of perovskite field-effect transistors. The effects of temperature, light, and measurement conditions are taken into account, as well as the physics of the device and the fundamental mechanisms that drive these devices, such as ion migration and ionic defects. Subsequently, the performance of perovskite transistors and phototransistors described so far is analyzed and critically evaluated. Finally, the major roadblocks to perovskite transistor advancement are identified and explored. The lessons learned from other perovskite optoelectronic devices are investigated in order to address these obstacles and bring these devices closer to industrial implementation.

Enhancing Optoelectronic Performance of All-Inorganic Double Perovskites via Halogen Doping: Synergistic Screening Strategies and Multiscale Simulations.

Designing all-inorganic double perovskites through element mixing is a promising strategy to enhance their optoelectronic performance and structural stability. The complex interplay between multilevel structures and optoelectronic properties in element-mixed double perovskites necessitates further in-depth theoretical exploration. In this study, we employ screening strategies and multiscale simulations combining first-principles methods and device-scale continuum models to identify two novel element-mixed compounds, Rb2AgInCl3I3 and Cs2AgInCl3I3, as promising candidates for photovoltaic applications. These compounds exhibit favorable structural factors and suitable direct band gaps. Theoretical investigations using first-principles methods with the HSE06 functional reveal direct band gaps of 0.98 and 1.26 eV for Rb2AgInCl3I3 and Cs2AgInCl3I3, respectively, with corresponding optical absorption coefficients exceeding 105 cm-1 in the visible light range. Cs2AgInCl3I3 features high charge mobilities of approximately 20 cm2·V-1·s-1 and a notable single-junction spectroscopic limited maximum efficiency (SLME) of 25.54%. Further analysis using the device-scale continuum model simulated the nonradiative recombination effects on power conversion efficiency, integrating quantum-mechanically calculated optoelectronic properties. These theoretical investigations, which bridge composition engineering with multiscale simulations, provide valuable insights into screening novel, lead-free, halogen-mixed double metal perovskite optoelectronic devices, highlighting their potential for high-performance solar energy applications.

Nanometer-Resolved Mapping of Organic Cation Migration Behavior in Methylammonium Lead Halide Perovskites.

The performance and stability of organic metal halide perovskite (OMHP) optoelectronic devices have been associated with ion migration. Understanding of nanoscale resolved organic cation migration mechanism would facilitate structure engineering and commercialization of OMHP. Here, we report a three-dimensional approach for in situ nanoscale infrared imaging of organic ion migration behavior in OMHPs, enabling to distinguish migrations along grain boundary and in crystal lattice. Our results reveal that organic cation migration along OMHP film surface and grain boundaries (GBs) occurs at lower biases than in crystal lattice. We visualize the transition of organic cation migration channels from GBs to volume upon increasing electric field. The temporal resolved results demonstrate the fast MA+ migration kinetics at GBs, which is comparable to diffusivity of halide ions. Our findings help understand the role of organic cations in the performance of OMHP devices, and the proposed approach holds broad applicability for revealing migration mechanisms of organic ions in OMHPs based optoelectronic devices.

Optoelectronics of Lead‐Free Antimony‐ and Bismuth‐Based Metal Halides for Sensitive and Low‐Noise Photodetection

AbstractOrganic–inorganic hybrid halide perovskites have emerged as the most promising optoelectronic materials for next‐generation solution‐processed devices, primarily attributed to their distinctive properties such as cost‐effectiveness, facile fabrication process, high light absorption coefficient, tunable bandgap, and relatively high charge carrier mobility. Nevertheless, the presence of Pb elements is inevitable in most high‐performance perovskite optoelectronic devices, posing environmental pollution concerns and impeding their commercialization. In this study, two novel non‐toxic bismuth‐ and antimony‐based perovskite materials with environmentally conscious approaches are developed. Their structures and optoelectronic properties have been systematically characterized. Subsequently, photoconductive‐ and photodiode‐type photodetectors are designed and fabricated. Notably, the photodiode configuration exhibits exceptionally low dark current and noise, superior detection sensitivity, fast response speed, and good device stability. Owing to these superior performance metrics, the devices demonstrate great potential for real applications. Furthermore, this study furnishes a theoretical framework and design perspectives for the solution‐processed semiconductor materials.

Quantum Transport and Spectroscopy of 2D Perovskite/Graphene Heterostructures

AbstractUnderstanding the quantum transport properties of (Two‐dimensional) 2D perovskite heterostructures is key to interpreting their electronic performance and promoting optoelectronic devices. Here, it is shown that clear Shubnikov‐de Hass oscillation appears in the heterostructure of monocrystalline 2D perovskites and graphene, thanks to the clean interface. An efficient charge transfer between perovskite nanosheets and graphene is found, facilitating the separation of electrons and holes at the interface. The relation between the charge transfer efficiency and microscopic interface structures is quantitatively described. The evidence of photo‐assisted transport from the photo‐response of magnetoresistance is revealed, which happens between Landau levels of two graphene layers mediated by hot carriers in the perovskite layer, overcoming the barrier from the organic layers in the Ruddlesden‐Popper perovskite phase. These results provide a picture to understand the transport behavior of 2D perovskite/graphene heterostructure and a reference for the controlled design of interfaces in perovskite optoelectronic devices.

Synchrotron Radiation-Based In Situ GIWAXS for Metal Halide Perovskite Solution Spin-Coating Fabrication.

Solution-processable perovskite-based devices are potentially very interesting because of their relatively cheap fabrication cost but outstanding optoelectronic performance. However, the solution spin-coating process involves complicated processes, including perovskite solution droplets, nucleation of perovskite, and formation of intermediate perovskite films, resulting in complicated crystallization pathways for perovskite films under annealing. Understanding and therefore controlling the fabrication process of perovskites is difficult. Recently, synchrotron radiation-based in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) techniques, which possess the advantages of high collimation, high resolution, and high brightness, have enabled to bridge complicated perovskite structure information with device performance by revealing the real-time crystallization pathways of perovskites during the spin-coating process. Herein, the developments of synchrotron radiation-based in situ GIWAXS are discussed in the study of the crystallization process of perovskites, especially revealing the important crystallization mechanisms of state-of-the-art perovskite optoelectronic devices with high performance. At the end, several potential applications and challenges associated with in situ GIWAXS techniques for perovskite-based devices are highlighted.

Plasmonic perovskite photodetector with high photocurrent and low dark current mediated by Au NR/PEIE hybrid layer

Hybrid organic-inorganic perovskite photodetectors have gained significant attention due to their superior potential for optoelectronic applications, offering various advantages such as low-cost processing, high charge carrier mobility, and lightweight properties. However, these perovskite photodetectors exhibit relatively low absorption in the near-infrared (NIR) range, which limits their potential applications. Here, to address this challenge, the integration of gold nanorods (Au NR) utilizing localized surface plasmon resonance (LSPR) effects in the NIR range has been developed, leading to enhanced light absorption in the active region and higher photocurrent generation. Additionally, ∼7.9 nm of thin polyethyleneimine ethoxylated (PEIE) interlayers were incorporated into the Au NR photodetectors, suppressing dark current by blocking charge injection. As a result, the synergistic effect of the Au NR/PEIE hybrid layer has led to a high-performance photodetector with a responsivity of 0.360 A/W and a detectivity of 1.81 × 1010 Jones, demonstrating a noticeable enhancement compared to the control device. Finite-difference time-domain (FDTD) simulations, morphological characterizations, and photoluminescence studies further support the mechanism for enhancing the performance of the device. We believe that our plasmon-enhanced protocol holds strong potential as a promising platform for perovskite optoelectronic devices.

Deciphering Structure and Charge Carrier Behavior in Reduced‐Dimensional Perovskites

AbstractReduced‐dimensional perovskites (RDPs) have advanced perovskite optoelectronic devices due to their tunable energy landscape, structure, and orientation. However, the origin of structural and photophysical property changes when moving from low‐dimensional to high‐dimensional RDPs remains to be understood. This study systematically reveals structural and photophysical properties of slot‐die‐coated Dion‐Jacobson (DJ) and Ruddlesden‐Popper (RP) RDPs with different dimensionalities. RP RDPs with lower dimensionality (n = 2) exhibit a dominant n = 2 phase, preferential out‐of‐plane orientation, and longer charge carrier lifetime compared with DJ RDPs. In addition, the formation kinetics of RDPs with higher dimensionality (n = 4) are unraveled by in situ X‐ray scattering, showing the favorable formation of the lower‐n phase in RP RDPs. The formation of these lower‐n phases is thermodynamically and stoichiometrically favored, while these phases are likely in the form of an “intermediate phase” which bridges the 3D‐like and lower‐n phases in DJ RDPs. DJ RDPs with higher dimensionality demonstrate comparable phase purity, preferential orientation, spatially vertical phase homogeneity, and longer charge carrier lifetime. As such, DJ‐based perovskite solar cells (PSCs) (n = 4) demonstrate better photostability under operational conditions than RP‐based PSCs. Thus, the work paves the way for the utilization of RDPs to upscale PSCs.

Perovskite versus Standard Photodetectors.

Perovskites have been largely implemented into optoelectronics as they provide several advantages such as long carrier diffusion length, high absorption coefficient, high carrier mobility, shallow defect levels and finally, high crystal quality. The brisk technological development of perovskite devices is connected to their relative simplicity, high-efficiency processing and low production cost. Significant improvement has been made in the detection performance and the photodetectors' design, especially operating in the visible (VIS) and near-infrared (NIR) regions. This paper attempts to determine the importance of those devices in the broad group of standard VIS and NIR detectors. The paper evaluates the most important parameters of perovskite detectors, including current responsivity (R), detectivity (D*) and response time (τ), compared to the standard photodiodes (PDs) available on the commercial market. The conclusions presented in this work are based on an analysis of the reported data in the vast pieces of literature. A large discrepancy is observed in the demonstrated R and D*, which may be due to two reasons: immature device technology and erroneous D* estimates. The published performance at room temperature is even higher than that reported for typical detectors. The utmost D* for perovskite detectors is three to four orders of magnitude higher than commercially available VIS PDs. Some papers report a D* close to the physical limit defined by signal fluctuations and background radiation. However, it is likely that this performance is overestimated. Finally, the paper concludes with an attempt to determine the progress of perovskite optoelectronic devices in the future.

Nanometer‐Resolved Mapping of Organic Cation Migration Behavior in Methylammonium Lead Halide Perovskites

AbstractThe performance and stability of organic metal halide perovskite (OMHP) optoelectronic devices have been associated with ion migration. Understanding of nanoscale resolved organic cation migration mechanism would facilitate structure engineering and commercialization of OMHP. Here, we report a three‐dimensional approach for in situ nanoscale infrared imaging of organic ion migration behavior in OMHPs, enabling to distinguish migrations along grain boundary and in crystal lattice. Our results reveal that organic cation migration along OMHP film surface and grain boundaries (GBs) occurs at lower biases than in crystal lattice. We visualize the transition of organic cation migration channels from GBs to volume upon increasing electric field. The temporal resolved results demonstrate the fast MA+ migration kinetics at GBs, which is comparable to diffusivity of halide ions. Our findings help understand the role of organic cations in the performance of OMHP devices, and the proposed approach holds broad applicability for revealing migration mechanisms of organic ions in OMHPs based optoelectronic devices.

Solution-Induced surface modification and secondary grains growth for high-performance and stable perovskite solar cells

Enhancing the quality of perovskite layer and refining the interface between the perovskite layer and the hole transport layer (HTL) represent pivotal strategies for optimizing the efficiency and stability of perovskite solar cells (PSCs). We accomplished this by employing a solution isopropanol (IPA), capable of selectively dissolving residual unreacted methylammonium and formamidine salts on the perovskite surface while preserving the integrity of lead iodide. Through control of the immersion time, we facilitated secondary crystal growth on the top of perovskite film. The resultant treated film exhibited a markedly suitable bandgap position and a diminished presence of residual trips. The IPA-treated sample led to a noteworthy photovoltaic conversion efficiency (PCE) of 23.34 %, compared to 21.46 % efficiency for untreated control sample. Furthermore, under sustained illumination at AM 1.5G with 25 % relative humidity, the uncovered IPA-treated sample retained an impressive 92 % of their initial efficiency after 1000 h. Further scrutiny revealed that this solution-based treatment effectively passivated trips, enhanced perovskite film quality, established novel built-in electric fields, and mitigated charge carrier recombination. This work provides a simple perovskite film treatment approach that does not require complex molecular engineering and can be applied not only to PSCs but also to other perovskite optoelectronic devices.

Effect of Metal-Organic Frameworks with Different Ligand Structures (ZIF-11 & ZIF-23) on the Optoelectronic Performance of Perovskite Photodetectors.

Crystal engineering using passivation to reduce perovskite defects is crucial to improving the quality of perovskite crystals and optoelectronic properties. Because of their unique properties, metal-organic framework materials have been used as an emerging and effective passivator for perovskite materials and optoelectronic devices. This paper focuses on the differences in the optoelectronic properties of zeolite imidazolium ester framework materials (ZIF-11 & ZIF-23) doped with different conjugated ring ligands for perovskite photodetectors. This paper proposes a simple and effective method to dope zeolite imidazolium ester framework nanoparticles (ZIF-11 & ZIF-23) into organic-inorganic perovskite MAPbI3 films. The crystalline quality of the perovskite films was improved after doping with ZIF-11 and ZIF-23. Meanwhile, the performance of the planar photoconductive devices was significantly improved. The photoresponsivity of the photodetector doped with ZIF-23 was 0.185A/W, and the detectivity was 4.22 × 1012 Jones. The photoresponsivity of the photodetector doped with ZIF-23 was 0.164 A/W, and the detectivity was 3.27 × 1012 Jones. The devices maintained long-time operational stability, operating without significant degradation for 480 s under the 1.2 V bias voltage operating condition. In addition, we observed a significant suppression of the ion migration process in ZIF-23 for a voltage-controlled ion migration process. The potential application of perovskite and MOF heterojunction materials for image information acquisition and storage is demonstrated.

CsPbI3 Perovskite Quantum Dot-Based WORM Memory Device with Intrinsic Ternary States.

The migration of mobile ionic halide vacancies is usually considered detrimental to the performance and stability of perovskite optoelectronic devices. Taking advantage of this intrinsic feature, we fabricated a CsPbI3 perovskite quantum dot (PQD)-based write-once-read-many-times (WORM) memory device with a simple sandwich structure that demonstrates intrinsic ternary states with a high ON/OFF ratio of 103:102:1 and a long retention time of 104 s. Through electrochemical impedance spectroscopy, we proved that the resistive switching is achieved by the migration of mobile iodine vacancies (VIs) under an electric field to form conductive filaments (CFs). Using in situ conductive atomic force microscopy, we further revealed that the multilevel property arises from the different activation energies for VIs to migrate at grain boundaries and grain interiors, resulting in two distinct pathways for CFs to grow. Our work highlights the potential of CsPbI3 PQD-based WORM devices, showcasing intrinsic multilevel properties achieved in a simple device structure by rationally controlling the drift of ionic defects.

Enhanced ambient-stability and charge transport property of the CsPbBr3@Polyaniline

Although all-inorganic lead halide perovskites (CsPbX3 (X = Cl, Br, I)) have received widespread attention due to excellent optoelectronic properties, their low carrier mobility and poor stability have limited their application in photodetection. In this study, to alleviate these problems, CsPbBr3@Polyaniline composite is fabricated by passivating CsPbBr3 quantum dots (QDs) into a CSA-doped polyaniline conducting polymer. Notably, polyaniline is employed as a protective layer to block the structure damage of CsPbBr3 QDs against water, light and heat. The contact between polyaniline and CsPbBr3 QDs forms a type II heterojunction for charge transfer, which greatly reduces the recombination rate of charge carriers compared to pristine CsPbBr3 QDs. Benefiting from the high stability and enhanced charge mobility, CsPbBr3@Polyaniline-based photodetector achieves improved photocurrent signal and optical response time. The results demonstrate that the surface passivation could resolve the crucial stability problem and simultaneously facilitate the superior performance of perovskite optoelectronic devices.

Perovskite Grown in Gallium Nitride Nanowire Matrix for Stable and High‐Efficiency X‐Ray Detection

AbstractHigh‐quality quasi‐2D perovskites in a GaN nano‐wire matrix are grown to build a 3D hetero‐structure for high‐performance X‐ray sensing. In the 3D hetero‐structure, GaN nano‐wire matrix serves as an n‐type charge collector that can rapidly extract carriers through the bulk film of the perovskite layer. Together with a p‐type top electrode, a p–i–n diode with the 3D hetero‐structure is built, that exhibits a rectified current–voltage characteristic. After analyzing the interface energy alignment, it is found that the fermi levels of the perovskite and GaN are aligned in the dark, and a quasi‐fermi level splits upon illumination, introducing a built‐in electrical field at the interface. As a result, strong photo‐induced current is observed from the diode without an external field. Finally, the 3D diode for X‐ray detection demonstration is used, revealing a sensitivity of 308.9 µC Gyair−1 cm−2 at an exceptionally low applied field of 0.125 V µm−1. The X‐ray‐induced signal from the 3D diode is stable after 155 cycles of X‐ray irradiation under a constant electric field. This demonstration informs a new 3D architecture for high‐performance X‐ray sensing, and it shows that GaN is a robust n‐type interface for perovskite optoelectronic devices.

Controlling Tin Halide Perovskite Oxidation Dynamics in Solution for Perovskite Optoelectronic Devices.

As a leading contender to replace lead halide perovskites, tin-based perovskites have demonstrated ever increasing performance in solar cells and light-emitting diodes (LEDs). They tend to be processed with dimethyl sulfoxide (DMSO) solvent, which has been identified as a major contributor to the Sn(II) oxidation during film fabrication, posing a challenge to the further improvement of Sn-based perovskites. Herein, we use NMR spectroscopy to investigate the kinetics of the oxidation of SnI2, revealing that autoamplification takes place, accelerating the oxidation as the reaction progresses. We propose a mechanism consistent with these observations involving water participation and HI generation. Building upon these insights, we have developed low-temperature Sn-based perovskite LEDs (PeLEDs) processed at 60 °C, achieving enhanced external quantum efficiencies (EQEs). Our research underscores the substantial potential of low-temperature DMSO solvent processes and DMSO-free solvent systems for fabricating oxidation-free Sn-based perovskites, shaping the future direction in processing Sn-containing perovskite materials and optoelectronic devices.