Inorganic Cesium Lead Halide Perovskite Research Articles

Surface stability and morphological transformations of CsPbI3

Metal-halide perovskites, particularly inorganic cesium-lead halide perovskites, have emerged as exceptional candidates for several technological applications in the 21st century, such as photovoltaic devices, optoelectronic and photocatalysis. This study systematically investigates the CsPbI3 surfaces through density functional theory (DFT) simulations and morphological analyses. The (001), (110), and (111) surfaces were investigated in terms of their possible terminations (here named α, β, γ, δ and ε), where the relations between their outermost coordination polyhedra, bond lengths, charge distribution, electronic and morphological properties were revealed. The results demonstrate that the (001) and (110) surfaces stand out as the most stables, with Esurf001-α=Esurf110-γ=0.08J/m2. Concerning the electronic properties, it is observed that the (110) and (111) present α terminations with acceptor states, while the β with donor states, making it possible to tune the system semiconducting behavior (n or p-type) via surface termination control. The Wulff construction was employed to show that (001), (110) and (111) surface stabilizations can produce cubic, dodecahedral and octahedral nanocrystal morphologies, respectively. By probing the depths of CsPbI3 surfaces, this research advances new concepts about the design and functionalization of perovskite halide, offering a crucial direction for experimental synthesis strategies.

Improved photoluminescence stability and defect passivation in SbBr3 post-treated CsPbBr3 quantum dots under ambient conditions.

Inorganic cesium lead halide perovskites have evoked wide popularity because of their excellent optoelectronic properties, high photoluminescence (PL) quantum yield (PLQY), and narrowband emission. Here, cesium lead bromide (CsPbBr3 ) quantum dots (QDs) were synthesized via the ligand-assisted re-precipitation method. Post-synthesis treatment of CsPbBr3 QDs using antimony tribromide improved the PL stability and optoelectronic properties of the QDs. In addition, the PLQY of the post-treated sample was enhanced to 91% via post-treatment, and the luminescence observed was maintained for 8 days. The post-synthesis treatment ensured defect passivation and improved the stability of CsPbBr3 perovskite QDs. High-resolution transmission electron microscopy revealed the presence of more ordered, uniform-sized CsPbBr3 QDs after post-synthesis treatment, and the uniformity of the sample improved as the day passed. The formation of a mixed crystal phase was observed from X-ray diffraction in both as-synthesized, as well as post-treated QDs samples with the possibility of a polycrystalline nature in the post-treated CsPbBr3 QDs as per the selected area electron diffraction pattern. The X-ray photoelectron spectroscopy spectra confirmed the presence of antimony and the possibility of defect passivation in the post-treated samples. These QDs can act as potential candidates in various optoelectronic applications such as photodetectors and light-emitting diodes due to their high PLQY and longer lifetime.

Limitations and Progresses in Carbon-Based Cesium Lead Halide Perovskite Solar Cells.

Inorganic cesium lead halide perovskites (CsPbIx Br3-x , 0≤x≤3) are promising alternatives with great thermal stability. Additionally, the choice of moisture-resistive and dopant-free carbon as the electrode material can simultaneously solve the problems of stability and cost. Therefore, carbon electrode-based inorganic PSCs (C-IPSCs) represent a promising candidate for commercialization, yet both the efficiencies and stability of related devices demand further progress. This article reviews the recent advancement of C-IPSCs and then unravels the distinctive merits and limitations in this field. Subsequently, our perspective on various modification strategies is analyzed on a methodological level. Finally, this article outlooks the promising research contents and the remaining unresolved issues in this field. We believe that understanding and analyzing the related problems in this field are instructive to stimulate the future development of C-IPSCs.

A dual emitting CsPbBr3/Eu-BDC composite as a ratiometric photoluminescent turn-on probe for aliphatic amine sensing.

The impressive photoluminescence properties of all inorganic cesium lead halide perovskite quantum dots (PeQDs) make them highly intriguing for fluorescence chemosensor applications. Herein, a ratiometric dual emitting perovskite-based sensor was designed by synthesizing fluorescent CsPbBr3 PeQDs in situ within a matrix of Eu-BDC (Eu(III) benzene-1,4-dicarboxylate). The results presented here establish the suggested sensor's quick and selective turn-on PL response to volatile primary aliphatic amine derivatives. In the presence of amines, the designed CsPbBr3/Eu-BDC sensor exhibits an enhancement of the PL signal of CsPbBr3 at 518 nm and the Eu-BDC signal at 615 nm served as a standard for constructing the ratiometric sensing system. Thereby, a visual color change from red to green was observed with the incremental addition of methylamine to the probe. A low detection limit of 0.083 ppm was determined for methylamine. In both the solution and vapor phases, this ratiometric sensor responds to a variety of primary aliphatic amines with very quick and strong fluorescence. Moreover, the sensor was effectively used for monitoring meat spoilage owing to the emission of biogenic amine vapor from meat products.

Gd-Ho-Dy]:CsPbI1.8Br1.2 stable perovskite material as an absorber layer in photovoltaic devices, charge storage electrode, and an efficacious OER/HER catalyst

Current work presents the first report based on the all inorganic cesium lead halide perovskite material (CsPbI1.8Br1.2) doped with the rare earth oxides (gadolinium-holmium-dysprosium) leading to a synergistic [Gd-Ho-Dy]:CsPbI1.8Br1.2 semiconductor system. The developed system expressed impressive stability at ambient conditions for 28 days with the bandgap energy spanning between 1.65 and 1.69 eV. This perovskite material has characteristic ABX3 cubic black phase crystalline geometry with the 33.57 nm crystallite size. Fabricated thin films were highly compact with maximum coverage and were totally devoid of any pinholes. The perovskite solar cell device using [Gd-Ho-Dy]:CsPbI1.8Br1.2 as an absorber layer achieved an efficiency of 13.25% and open circuit voltage of 1.2 V. [Gd-Ho-Dy]:CsPbI1.8Br1.2/nickel foam electrode expressed an excellent charge storage potential with the specific capacitance of 406 F g−1 and lower series resistance of 0.58 Ω besides exhibiting stability for longer duration. [Gd-Ho-Dy]:CsPbI1.8Br1.2 is also a bi-functional electro-catalyst with the greater tendency for hydrogen evolution shown by a lower overpotential (ηHER) and Tafel values of 148 mV and 122.8 mV dec−1 than oxygen evolution. The endurance testing coupled with stability proved by other analyses is indicative of the candidature of developed material in different energy devices, systems, and applications.

Stabilization of CsPbBr3 Nanocrystals via Defect Passivation and Alumina Encapsulation for High-Power Light-Emitting Diodes

The instability of inorganic cesium lead halide perovskite quantum dots (QDs) limits their commercial applications. Here, a streamline surface nanotailoring strategy combining defect passivation and alumina infiltration and encapsulation via atomic layer deposition was employed to improve the luminescence properties and stability of QD films. Didodecyl dimethyl ammonium bromide with oleic acid pretreatment was used to reduce nonradiative recombination and photoluminescence quenching through strong bonding. Al2O3 infiltrated through the gaps between the QDs with ng precision control and formed a dense encapsulation barrier, which separated QDs from the influence of the external environment. The fluorescence lifetime and the overall stability of the obtained QD films were greatly improved, which have application prospects in high-power white light-emitting diodes.

Influence of the Surface Modification on Carrier Kinetics and ASE of Evaporated Perovskite Film

All inorganic cesium lead halide perovskite has emerged as promising optical gain materials due to its excellent optical properties. Carrier recombination and amplified spontaneous emissions (ASE) threshold affect their performance on lasing applications. Herein, CsPbBr3 films were prepared using thermally evaporated method with uniform and high coverage surface. Ammonium salt (PABr) was used to further modify the film. The modified sample exhibited flattened surface morphology, enhanced light-emission, suppressed trap-assisted recombination and Auger recombination, thus improving the efficiency of radiation recombination. It was found that the PABr modified CsPbBr3 exhibit an ASE threshold of 25.45 uJ cm−2 which is lower than that of pure CsPbBr3 with 31.5 uJ cm−2. This work suggest that the thermally evaporated method interfacial modification could provide an effective strategy to ameliorate the room-temperature stimulated emission of CsPbBr3.

Additive-Enhanced Crystallization of Inorganic Perovskite Single Crystals for High-Sensitivity X-Ray Detection.

Inorganic cesium lead halide perovskite single crystals are particularly intriguing to ionizing radiation detection by virtue of their material stability and high attenuation coefficients. However, the growth of high-quality inorganic perovskite single crystals remains challenging, mainly due to the limited solubility. In this work, an additive-enhanced crystallization method is proposed for cesium lead perovskites. The additive can remarkably increase the solubility of cesium bromide in dimethyl sulfoxide (DMSO) forming a balanced stoichiometric precursor solution, which prevents the formation of impurity phases. In addition, the additives would react with DMSO generating glyoxylic acid (GLA) via nucleophilic substitution and Kornblum oxidation reactions. The GLA can form stable PbBr2 -DMSO-GLA complexes, which enables better crystallinity, uniformity and much longer carrier lifetimes for the grown single crystals. The X-ray detectors using the additive-enhanced crystals exhibit an ultra-high sensitivity of 3.0 × 104 µC Gyair -1 cm-2 which is more than two orders of magnitude higher than that for the control devices.

Understanding the synergistic influence of the propylammonium bromide additive and erbium-doped CsPbI2Br for highly stable inorganic perovskite solar cells

Inorganic cesium lead halide perovskites have gained increasing attention to boost photovoltaic performance and device stability.

ZnI2 post-processing of CsPbBr3 quantum dots for red, stable, and low-threshold amplified spontaneous emission

All inorganic cesium lead halide perovskite (CsPbX3; X = Cl, Br, or I) quantum dots (QDs) have received widespread attention as a class of favorable optical gain materials. The key issue of CsPbX3 perovskites is their instability under light or exposure to air. Notably, the inherent phase instability of CsPbI3 QDs severely restricts the development of red-light emission. Herein, we propose a simple method to post-process CsPbBr3 QDs with a ZnI2 solution. The prepared CsPbBryI3−y (named CPBI-z, where z corresponds to the photoluminescence peaks' position) QDs exhibit adjustable photoluminescence in the range of 550–640 nm. The photoluminescence quantum yield is increased from 73.3% to 97.2% as the surface defects of QDs are passivated by I− and Zn2+. Compared with the pristine CsPbBr3 QDs, the post-processed QDs are more stable under ultraviolet irradiation and in the air. Aside from that, under 532 nm nanosecond laser excitation, CPBI-z QD films exhibit excellent amplified spontaneous emission performance. The CPBI-640 QD film shows a low threshold, 102 μJ cm−2 for red stable amplified spontaneous emission.

CsPbBr3 nanocrystals embedded glass enables highly stable and efficient light-emitting diodes

All inorganic cesium lead halide perovskite nanocrystals have great potential for electrically pumped or optically pumped light emitting diodes. External quantum efficiency of electrically pumped perovskite nanocrystals-based light emitting diodes are strongly affected by the imbalanced charge injection, electric field induced ion diffusion and joule heating. External quantum efficiency of optically pumped perovskite nanocrystals-based light emitting diodes are also affected by their photo-stability and photoluminescence quantum efficiency. Here, highly efficient light-emitting diodes are realized by employing CsPbBr3 nanocrystals embedded glasses as color converter. It is found that increase in molar ratio between bromine and lead in glasses results in the passivation of bromine vacancies of CsPbBr3 nanocrystals, and significantly improves photoluminescence quantum efficiency and photo-stability of CsPbBr3 nanocrystals embedded glasses. With these CsPbBr3 nanocrystals embedded glasses as color converter, highly efficient green light-emitting diodes with external quantum efficiency of 33.72% and white light-emitting diodes with external quantum efficiency of 43.27% are realized. These results demonstrate that cesium lead halide perovskite nanocrystals embedded glasses are promising for optically pumped light-emitting diodes.

Luminescent Thin Films Enabled by CsPbX3 (X=Cl, Br, I) Precursor Solution.

Inorganic cesium lead halide perovskite nanocrystals are candidates for lighting and display materials due to their outstanding optoelectronic properties. However, the dissolution issue of perovskite nanocrystals in polar solvents remains a challenge for practical applications. Herein, we present a newly designed one-step spin-coating strategy to prepare a novel multicolor-tunable CsPbX3 (X=Cl, Br, I) nanocrystal film, where the CsPbX3 precursor solution was formed by dissolving PbO, Cs2 CO3 , and CH3 NH3 X into the ionic liquid n-butylammonium butyrate. The as-designed CsPbX3 nanocrystal films show high color purity with a narrow emission width. Also, the blue CsPb(Cl/Br)3 film demonstrates an absolute photoluminescence quantum yields (PLQY) of 15.6 %, which is higher than 11.7 % of green CsPbBr3 and 8.3 % of red CsPb(Br/I)3 film. This study develops an effective approach to preparing CsPbX3 nanocrystal thin films, opening a new avenue to design perovskite nanocrystals-based devices for lighting and display applications.

Multidentate ligand passivation enabled enhanced photoluminescence and stability of CsPbBr3 nanocrystals for white light-emitting diodes

Inorganic cesium lead halide perovskite nanocrystals (NCs) show promising application in the field of optoelectronic devices. However, the poor stability and low photoluminescence quantum yield (PLQY) have been a huge hurdle for practical applications. Ligand engineering strategy was proven to be an effective way to improve the stability and PLQY. Herein, we utilize a multidentate ligand of Boc-D-Glutamic acid (BDGA) to treat the perovskite NCs, enabling exceptional quantum yield approaching 100% and superior colloidal stability (about 10% reduction after 60 days storage at ambient conditions), as well as greatly enhanced resistance to thermal treatment and UV irradiation which can be ascribed to the surface defect passivation and an efficient ligand exchange with robust affinity and/or compensation. Besides, the as-fabricated white light-emitting diodes (WLEDs) exhibits a high luminous efficiency of 93.5 lm/W and a wide color gamut (128% of the National Television System Committee and 95% Rec. 2020). This work provides a facile route to realize high PLYQ and improve the challenging stability issue in perovskite NCs.

CsPbBr3 microarrays with tunable periodicity, optoelectronic and field emission properties using self-assembled polystyrene template and co-evaporation method.

The booming growth of all inorganic cesium lead halide perovskites in optoelectronic applications has prompted extensive research interest in the fabrication of ordered nanostructures or microarrays for enhanced device performances. However, the high cost and complexity of commercial lithographic approaches impede the facile fabrication of perovskite microarrays. Herein, CsPbBr3 microarrays with tunable periodicities have been fabricated using a self-assembled polystyrene nanosphere template and a co-evaporation method. The periodicity of CsPbBr3 microarrays is precisely manipulated by simply modifying the size of polystyrene nanospheres. These microarrays are beneficial for light harvesting, leading to better light absorption ability and prolonged photoinduced carrier lifetime. The longest average carrier lifetime of 58.3 ns is obtained for CsPbBr3 microarrays with a periodicity of 1.0 μm. More importantly, the periodic structures of CsPbBr3 microarrays result in a tunable density of emitter tips in field emission devices. Compared to compact CsPbBr3 films, a 68.2% decrease of the turn-on field is observed for CsPbBr3 microarrays when the periodicity is 150 nm. The higher density of emitter tips leads to larger local field enhancement, and hence the largest field enhancement factor of 3346.6. Finally, a good emission current stability for CsPbBr3 microarray-based field emission devices has been demonstrated.

Phase‐Control of Single‐Crystalline Inorganic Halide Perovskites via Molecular Coordination Engineering

AbstractThe excellent optoelectronic properties and structural stability of inorganic cesium lead halide perovskites make them promising candidates for multiple types of optoelectronic devices. However, it remains a challenge to fabricate monocrystalline phase‐pure perovskite microstructures by facile low‐temperature solution‐based methods. Herein, a solution‐based method is demonstrated for controlling the crystallization of cesium halide perovskite microstructures. The structure of perovskite crystals is successfully tuned from non‐corner sharing Cs4PbBr6 (0D) to corner‐sharing CsPbBr3 (3D) to layered CsPb2Br5 (2D) by controlling water (H2O) to dimethylsulfoxide (DMSO) ratios. Molecular dynamics simulations and thermodynamic analysis indicate that the relative stability of Pb2+ and Br− ions in solution is the key factor in determining which crystals form at different H2O/DMSO ratios, with Cs+ simply incorporated as needed. The phase‐pure 0D crystals exhibit a high photoluminescence quantum yield of 41%, whilst the 2D crystals have an onset of absorption at 350 nm. Furthermore, the as‐synthesized, highly uniform 3D perovskite single crystals are coupled with nanofabricated interdigitated electrodes to show excellent X‐ray detection, with a high sensitivity of 8000 μC Gyair−1cm−2 obtained under a 0.5V external bias. This is comparable to many commercial X‐ray detectors (Si, α‐Se) and several times higher than other reported inorganic perovskite materials (CsPbBr3 quantum dots, Cs2AgBiBr6).

Enhanced field emission properties of CsPbBr3 films by thermal annealing and surface functionalization with boron nitride

The relatively low work function, high defect tolerance, high electron mobility, and ease of fabrication nanostructures with high aspect ratio make all inorganic cesium lead halide perovskites promising emitter materials, but little research efforts have been devoted to them for potential applications in field emission devices. Herein, we report the enhanced field emission properties of CsPbBr3 films after thermal annealing and boron nitride modification. For as-grown CsPbBr3 films, the turn-on field at a current density of 10 μA cm−2 is 4.0 V μm−1, it decreases to 3.375 V μm−1 after thermal annealing at 150 °C, which is attributed to better crystallinity and formation of nanoscale emitter tips with sharp edges and optimized tips density. The field emission performance is further enhanced by surface functionalization with boron nitride deriving from the surface transfer induced n-type doping of CsPbBr3, and hence reduced work function. As a result, a lowest turn-on field of 2.875 V μm−1 and highest enhancement factor of 2518 are achieved. Finally, a good emission current stability of CsPbBr3 films after boron nitride modification have been demonstrated. The emission current fluctuations are 2.36% and 0.56% at initial current density of 20 and 100 μA/cm2, respectively.

Low-Threshold Amplified Spontaneous Emission from Air-Stable CsPbBr3 Perovskite Films Containing Trace Amounts of Polyethylene Oxide.

Organic additives can enhance the amplified spontaneous emission (ASE) performance of inorganic cesium lead halide perovskites (CsPbBr3 ) but volatility, potential hygroscopicity and oxidative degradation of these additives jeopardizes the thermal stability and shelf-life of blended CsPbBr3 films. To address this problem, we have fabricated perovskite films in a two-step solution protocol involving as little added polyethylene oxide (PEO) as possible. These films exhibited enhanced crystallization, improved photoluminescence (PL) intensity and prolonged lifetimes. Their hierarchical morphology and surface passivation lowered the ASE threshold from 278 to 176 μЈ/cm2 under one-photon nanosecond laser excitation. The proportion of added PEO was 0.3 wt% and was subsequently almost fully removed, thereby reducing its adverse influence on the stability of resulting films under continuous pulsed laser excitation. Stable ASE spectra could be stimulated after storage in air for 10 months.

Resonant Band-Edge Emissive States in Strongly Confined CsPbBr3 Perovskite Nanoplatelets

Strongly confined, fully inorganic cesium lead halide perovskite nanocrystals are of great promise for light-emitting devices in the blue spectral range owing to their high photoluminescence quantum yields. A combination of broadband fluorescence up-conversion and transient absorption spectroscopies was used to study early exciton dynamics in quasi-1D CsPbBr3 nanoplatelets (3 × 4 × 23 nm3, NPls). This allowed to reveal emitting band-edge states in the NPls that form instantaneously upon photoexcitation and then relax within the first picosecond to lower energy confined hole states (CHSs). The influence of the pump excitation intensity on the latter process was further scrutinized. The band-edge population lifetime was found to increase with the rise of the photon fluence due to CHS filling. When the concentration of NPls in solution becomes very high, nanoparticles overlap, resulting in a decrease in their external absorption cross-section and an increase in the emission Stokes shift due to photon reabsorption.

Electrical Loss Management by Molecularly Manipulating Dopant-free Poly(3-hexylthiophene) towards 16.93 % CsPbI2 Br Solar Cells.

Inorganic cesium lead halide perovskites offer a pathway towards thermally stable photovoltaics. However, moisture-induced phase degradation restricts the application of hole transport layers (HTLs) with hygroscopic dopants. Dopant-free HTLs fail to realize efficient photovoltaics due to severe electrical loss. Herein, we developed an electrical loss management strategy by manipulating poly(3-hexylthiophene) with a small molecule, i.e., SMe-TATPyr. The developed P3HT/SMe-TATPyr HTL shows a three-time increase of carrier mobility owing to breaking the long-range ordering of "edge-on" P3HT and inducing the formation of "face-on" clusters, over 50 % decrease of the perovskite surface defect density, and a reduced voltage loss at the perovskite/HTL interface because of favorable energy level alignment. The CsPbI2 Br perovskite solar cell demonstrates a record-high efficiency of 16.93 % for dopant-free HTL, and superior moisture and thermal stability by maintaining 96 % efficiency at low-humidity condition (10-25 % R. H.) for 1500 hours and over 95 % efficiency after annealing at 85 °C for 1000 hours.

Air-stable and low threshold amplified spontaneous emission via CsBr aqueous solution processed all-inorganic CsPbBr3 perovskite films

Inorganic cesium lead halide perovskite (CsPbX3, X = Cl, Br, and I) has attracted increasing attention in the field of laser application due to its excellent stability compared to the organic–inorganic hybrid perovskite since affording the radiation of a long pulse pump source requires high thermal stability of the material. However, it is difficult to observe the amplified spontaneous emission (ASE) of CsPbBr3 using a one-step solution method due to the low solubility of CsBr in the organic solvent. Herein, we fabricate a CsPbBr3 film with a two-step solution method and realize the ASE under the long pulse pumping. Meanwhile, a CsBr aqueous solution is used as an effective additive to increase the concentration of Cs+ in the precursor solution and then to improve the optical amplification properties of the CsPbBr3 films. The films exhibit better crystalline and enhanced photoluminescence intensity. Both the ASE threshold and gain have been significantly improved. Furthermore, the optimized film shows a satisfying stability of ASE after being placed in the air for more than two months.