All-inorganic CsPbBr3 Perovskite Research Articles

The mechanism of alkali doping in CsPbBr3: A first-principles perspective

All-inorganic CsPbBr3 perovskite doped with alkali metal atoms has been attracting increasing attention due to its superior optoelectronic properties. However, there still exists significant uncertainty regarding the doping mechanism. One view of the mechanism is that alkali metal atoms tend to substitute Cs in CsPbBr3 crystals. Another view is that Li and Na tend to intercalate into interstitial sites because their radii are much smaller than that of Cs. To elucidate the doping mechanism, it is necessary to investigate the point defects physics of alkali metal elements in CsPbBr3. In this work, by using first-principles calculations we find that alkali metal atoms energetically prefer to substitute for Cs or Pb atoms in CsPbBr3 crystals under different chemical potential conditions. To determine the alkali metal atoms doping site, one should consider the chemical potential of synthesis conditions, the dopant valence states, and atomic radii. Notably, alkali metal atoms doping mainly introduces shallow levels, which is helpful for improving the p-type conductivity of CsPbBr3.

An excellent impedance-type humidity sensor based on halide perovskite CsPbBr3 nanoparticles for human respiration monitoring

Abstract Humidity sensors with fast response, high accuracy and low-power consumption are critical importance in smart home and health monitoring applications. Herein, we demonstrate an excellent impedance relative humidity sensor based on all-inorganic halide perovskite CsPbBr3 nanoparticles (NPs) under low working-voltage (20 mV). The CsPbBr3 NPs humidity sensor exhibits fast response and recovery behavior at room temperature. Moreover, the sensor demonstrates excellent repeatability, low hysteresis and good stability. The humidity sensing mechanism of CsPbBr3 NPs is further studied and discussed by employing an electrochemical impedance spectroscopy measurement. Furthermore, the respiratory monitoring face mask based on CsPbBr3 humidity sensor shows accurate and stable performance, suggesting perovskite CsPbBr3 NPs based humidity sensor have great potential in future real-time health status monitoring applications.

Dimensionality Control of SnO2 Films for Hysteresis-Free, All-Inorganic CsPbBr3 Perovskite Solar Cells with Efficiency Exceeding 10.

The all-inorganic cesium lead bromide (CsPbBr3) perovskite solar cells (PSCs) have attracted considerable interest because of their outstanding environmental stability and low manufacturing cost. However, the state-of-the-art mesoscopic titanium dioxide (TiO2) electron-transporting layers (ETLs) always present low electron mobility, are destructive to perovskites under ultraviolet light illumination, as well as possess high sintering temperature. Nanostructured tin dioxide (SnO2) is a promising electron-transporting material for high-efficiency PSCs due to matching energy-level alignment with the perovskite layer, improved optical transparency, high electron mobility, excellent photostability, and low-temperature processing. Furthermore, rapid but poorly controlled perovskite crystallization makes it difficult to scale up planar PSCs for industrial applications. To address this issue, we adopt a dimensional SnO2 ETL to change the surface wettability for uniform perovskite coverage over large areas and the growth of large-sized CsPbBr3 grains, resulting in a maximum grain size of 1.65 μm. Moreover, the dimensional SnO2 ETL could increase the interfacial contact area between the CsPbBr3 layer and the ETL and enhance the electronic contact for efficient electron extraction to suppress or to eliminate the notorious hysteresis behavior. As expected, a power conversion efficiency (PCE) of 9.51% with an almost hysteresis-free phenomenon is achieved through dimensionality control of SnO2 films attributed to the remarkably enhanced light harvesting, accelerated electron extraction, diminished defect density, and reduced charge recombination. Upon further interfacial modification with graphene quantum dots (GQDs), the PSC based on the two-dimensional SnO2 ETL achieves a champion PCE of 10.34% due to the improved energy-level alignment at the device interface. Moreover, the best all-inorganic CsPbBr3 PSC free of encapsulation retains 93% of initial efficiency over 10 days at 80% relative humidity. This work provides an effective dimensionality control strategy for optimized charge transportation and enlarged perovskite grain size to make stable and efficient all-inorganic CsPbBr3 PSCs.

Flexible, All-Inorganic CsPbBr3 Perovskite Solar Cells Tailored by Heat-resistant Muscovite Substrates.

All-inorganic CsPbBr3 perovskite solar cells (PSCs) have attracted tremendous attention, owing to their excellent stability and rising power conversion efficiency. However, the mechanical flexibility of these solar cells has ground to a standstill because of the high-temperature requirement for ideal CsPbBr3 perovskite films. In this study, a flexible CsPbBr3 PSC with an efficiency of 5.71 % has been made by means of fabricating a heat-resistant conductive muscovite substrate, which demonstrates very high mechanical flexibility with nearly unchanged resistance even after 4000 bending cycles (12000 cycles of concave and convex bending for PSCs), owing to the weak van der Waals force and layered structure. Implementation of the muscovite substrate enables the fabrication of flexible PSCs under high-temperature conditions, providing a new path to increase the efficiency without lowering the crystallization temperature of state-of-the-art electron-transporting materials and perovskite films in the future.

Stability study of all-inorganic perovskite CsPbBr3 QDs@SiO2/EVA film composites prepared by one-step

CsPbX3 (X = Cl, Br, I) all-inorganic perovskite quantum dots have attracted extensive attention from researchers recently. However, the further development is confined by serious stability problems. In this work, the CsPbBr3 QDs@SiO2/EVA films were prepared by supersaturated recrystallization, and SEM, EDS, XRD, FT-IR and PL were used to study microstructure, phase composition, and optical properties. Results show that during the preparation process, the amounts of precursor added would affect the fluorescence emission intensity of materials. The preparation method of films is simple, easy to operate, low cost, and beneficial to commercial large-scale production. In a typical synthesis, PbBr2 and CsBr are dissolved in DMF, and then oleic acid (OA) and oleylamine (OAm) as ligands are added to stabilize the DMF−PbBr2−CsBr precursor solution. When the addition of TEOS is 0.06 mL, the PL peak strength of prepared films is higher and the thickness of CsPbBr3 QDs@SiO2/EVA films is about 100 μm and flexible enough to be bent. At room temperature, the retention of fluorescence intensity of films is 67.4% after 30 d in the air, the retention is 63.6% after 40 h in the water, and the retention is 72.1% after 40 h under the UV light. EVA resins and SiO2 coating can effectively isolate the contact between quantum dots and moisture and delay the intrusion of oxygen, which significantly improves the stability of pure quantum dots.

Multifunctional brominated graphene oxide boosted charge extraction for high-efficiency and stable all-inorganic CsPbBr3 perovskite solar cells

The perovskite film with large grain size and high charge mobility is critical for the improvement of the power conversion efficiency (PCE) and the operational stability of perovskite solar cells (PSCs). Herein, multifunctional brominated graphene oxide (Br-GO) is prepared and innovatively used as an effective additive to incorporate into CsPbBr3 to form a large-grained high-quality perovskite film and to passivate defects at grain boundaries, which remarkably reduces the trap state density and carrier non-radiative recombination. Meanwhile, the hole mobility of the homogeneous CsPbBr3 + Br-GO photoactive layer is obviously increased due to the hole acceptor properties and high carrier mobility of Br-GO, resulting in an enhanced charge separation as well as transfer and suppressed carrier radiative recombination. Moreover, the Br-GO with a downshift valence band is employed as a hole-transporting material setting at perovskite/Carbon interface to further compensate energy levels and promote hole extraction. As a consequence, a champion PCE of 10.10% with an open-circuit voltage up to 1.602 V for the optimized PSCs with a configuration of FTO/c-TiO2/m-TiO2/CsPbBr3 + Br-GO/Br-GO/Carbon is obtained, which is much higher than 6.28% efficiency for the reference device. The unencapsulated solar cells also exhibit a remarkable tolerance toward 85% RH and long-term AM 1.5G illumination in air.

Ultrathin and Conformable Lead Halide Perovskite Photodetector Arrays for Potential Application in Retina‐Like Vision Sensing

Solution-processed lead halide perovskites are considered one of the promising materials for flexible optoelectronics. However, the array integration of ultrathin flexible perovskite photodetectors (PDs) remains a significant challenge limited by the incompatibility of perovskite materials with manufacturing techniques involving polar liquids. Here, an ultrathin (2.4µm) and conformable perovskite-based PD array (10 × 10 pixels) with ultralight weight (3.12g m-2 ) and excellent flexibility, is reported. Patterned all-inorganic CsPbBr3 perovskite films with precise pixel position, controllable morphology, and homogenous dimension, are synthesized by a vacuum-assisted drop-casting patterning process as the active layer. The use of waterproof parylene-C film as substrate and encapsulation layer effectively protects the perovskite films against penetration of polar liquids during the peeling-off process. Benefitting from the encapsulation and ultrathin property, the device exhibits long-term stability in the ambient environment, and robust mechanical stability under bending or 50% compressive strain. More importantly, the ultrathin flexible PD arrays conforming to hemispherical support realize imaging of light distribution, indicating the potential applications in retina-like vision sensing.

Flexibly regulated electrochemiluminescence of all-inorganic perovskite CsPbBr3 quantum dots through electron bridge to across interfaces between polar and non-polar solvents

All-inorganic perovskite quantum dots (QDs) have attracted great interests due to its outstanding properties. But their poor stability in polar solvents seriously hampered wide applications in analytical chemistry. In this work, strong, stable and flexibly regulated the electrochemiluminescence (ECL) emission form CsPbBr3 QDs was successfully obtained and applied in the analysis of polar solvents through the unique structure of closed bipolar electrode (BPE). To demonstrate the feasibility, it was successfully used in the detection of tetracycline (Tc) aqueous solution. CsPbBr3 QDs was immersed into organic solution in anode microcell of closed BPE while Tc aqueous solution was added into cathode microcell. The two microcells were physically separated and would not interfere with each other. But the bio-recognition event between aptamer and Tc in cathode microcell would induce the ECL signal change in anode microcell through the electrons conducted by BPE as the bridge. The ECL emission can be flexibly regulated by environmental factors of both polar and non-polar solvents and the interface status of the BPE. Compared with traditional methods to overcome the intrinsic instability in polar medium, the reported method does not need any further surface modifications, has no limitations on the targets and can provide wide development space for further deep research, which may open a new direction for the ECL sensing of CsPbBr3 QDs.

Achieving Matrix Quantum Dot Light-Emitting Display Based on All-Inorganic CsPbBr₃ Perovskite Nanocrystal Composites

We present a display consisting of a 64-cell quantum dot (QD) light-emitting diodes (LEDs) array manufactured by spin coating and steel plate design evaporation technology. The QDLED pixels in the array can be driven independently. The surface of perovskite nanocrystal (NC) composite was modified by using pure natural material aloe-vera gel as the organic precursor to obtain high-quality narrow band photoluminescence emission all-inorganic CsPbBr3 perovskite NC composites. Here, an open-source Arduino microcontroller unit was used as the dynamic micro-control terminal, combined with a step-down module and four motor drive modules to make the display driver circuit. Finally, a 99% operating rate and a maximum brightness of 3366 cd $\text{m}^{-2}$ were achieved in the 8 $\times $ 8 perovskite QDLEDs array display. Furthermore, an electroluminescence dynamic pattern display based on a 64-cell QDLEDs array display has been successfully demonstrated. This study demonstrates the potential of perovskite devices for next-generation displays.

Enhanced hole extraction by electron-rich alloys in all-inorganic CsPbBr3 perovskite solar cells.

We present the fabrication of electron-rich Pt3M alloy-tailored carbon electrodes to maximize hole extraction. Through optimizing the doses and alloy species systematically, the best all-inorganic CsPbBr3 perovskite solar cell achieved a power conversion efficiency of 9.08% and showed excellent long-term stability at 80% RH over 20 days.

Corrigendum to “Write once read many times resistance switching memory based on allinorganic perovskite CsPbBr3 quantum dot”

Corrigendum to “Write once read many times resistance switching memory based on allinorganic perovskite CsPbBr3 quantum dot”

CsPbBr3 perovskite detectors with 1.4% energy resolution for high-energy γ-rays

Halide perovskite semiconductors are poised to revitalize the field of ionizing radiation detection as they have done to solar photovoltaics. We show that all-inorganic perovskite CsPbBr3 devices resolve 137Cs 662-keV γ-rays with 1.4% energy resolution, as well as other X- and γ-rays with energies ranging from tens of keV to over 1 MeV in ambipolar sensing and unipolar hole-only sensing modes with crystal volumes of 6.65 mm3 and 297 mm3, respectively. We report the scale-up of CsPbBr3 ingots to up to 1.5 inches in diameter with an excellent hole mobility–lifetime product of 8 × 10−3 cm2 V−1 and a long hole lifetime of up to 296 μs. CsPbBr3 detectors demonstrate a wide temperature region from ~2 °C to ~70 °C for stable operation. Detectors protected with suitable encapsulants show a uniform response for over 18 months. Consequently, we identify perovskite CsPbBr3 semiconductor as an exceptional candidate for new-generation high-energy γ-ray detection. Energy resolution of high-energy photon detectors is desired for applications ranging from biomedical imaging to homeland security. In this work, perovskite-based γ-ray detection with 1.4% energy resolution is demonstrated.

Static Rashba Effect by Surface Reconstruction and Photon Recycling in the Dynamic Indirect Gap of APbBr3 (A = Cs, CH3NH3) Single Crystals.

Recently, halide perovskites have gained significant attention from the perspective of efficient spintronics owing to the Rashba effect. This effect occurs as a consequence of strong spin-orbit coupling under a noncentrosymmetric environment, which can be dynamic and/or static. However, there exist intense debates on the origin of broken inversion symmetry since the halide perovskites typically crystallize into a centrosymmetric structure. In order to clarify the issue, we examine both dynamic and static effects in the all-inorganic CsPbBr3 and organic-inorganic CH3NH3PbBr3 (MAPbBr3) perovskite single crystals by employing temperature- and polarization-dependent photoluminescence excitation spectroscopy. The perovskite single crystals manifest the dynamic effect by photon recycling in the indirect Rashba gap, causing dual peaks in the photoluminescence. However, the effect vanishes in CsPbBr3 at low temperatures (<50 K) accompanied by a striking color change of the crystal, arising presumably from lower degrees of freedom for inversion symmetry breaking associated with the thermal motion of the spherical Cs cation compared with the polar MA cation in MAPbBr3. We also show that the static Rashba effect occurs only in MAPbBr3 below 90 K, presumably due to surface reconstruction via MA-cation ordering, which likely extends across a few layers from the crystal surface to the interior. We further demonstrate that this static Rashba effect can be completely suppressed upon surface treatment with polymethyl methacrylate (PMMA) coating. We believe that our results provide a rationale for the Rashba effects in halide perovskites.

Tailoring organic bulk-heterojunction for charge extraction and spectral absorption in CsPbBr3 perovskite solar cells

All-inorganic CsPbBr3 perovskite solar cells (PSCs) are promising candidates to balance the stability and efficiency issues of organic-inorganic hybrid devices. However, the large energy barrier for charge transfer and narrow spectral response are still two challenging problems for performance improvement. We present here an organic bulk-heterojunction {poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl C61 butyric acid methyl ester (P3HT: PCBM)} photoactive layer to boost the charge extraction and to widen the spectral absorption, achieving an enhanced power conversion efficiency up to 8.94% by optimizing the thickness of P3HT: PCBM photoactive layer, which is much higher than 6.28% for the pristine CsPbBr3 device. The interaction between the carbonyl group in PCBM and unsaturated Pb atom in the perovskite surface can effectively passivate the defects and reduce charge recombination. Furthermore, the coupling effect between PCBM and P3HT widens the spectral response from 540 to 650 nm for an increased short-circuit current density. More importantly, the devices are relatively stable over 75 days upon persistent attack by 70% relative humidity in air condition. These advantages of high efficiency, excellent long-term stability, cost-effectiveness and scalability may promote the commercialization of inorganic PSCs.

Enhanced Spin-Orbit Coupled Photoluminescence of Perovskite CsPbBr3 Quantum Dots by Piezo-Phototronic Effect.

Piezo-phototronic effect is a fundamental effect of semiconductors lacking of central symmetry with geometries from one-dimensional (1D) nanowire to 3D bulk. Here, we present that the piezo-phototronic effect can even tune a spin-orbit coupled photoluminescence (PL) based on all-inorganic perovskite CsPbBr3 quantum dots (QDs). Although the cubic structure of CsPbBr3 QDs is nonpiezoelectric, a cooling treatment can change it to an orthorhombic structure, which is proven to possess a piezoelectric property. The spin-orbit coupled PL intensity is demonstrated to be dependent on the polarization of the excited light. Because of the manipulation of the spin-split energy levels via the piezo-phototronic effect, the spin-orbit coupled PL intensities under a -0.9% compressive strain for linearly and circularly polarized light excitations can be enhanced by 136% and 146%, respectively. These findings reveal fundamental understandings of the spin-orbit coupled PL dynamics and demonstrate promising optoelectronic applications of the piezo-phototronic effect in these QDs.

Interfacial Strain Release from the WS2 /CsPbBr3 van der Waals Heterostructure for 1.7 V Voltage All-Inorganic Perovskite Solar Cells.

Perovskite lattice distortion induced by residual tensile strain from the thermal expansion mismatch between the electron-transporting layer (ETL) and perovskite film causes a sluggish charge extraction and transfer dynamics in all-inorganic CsPbBr3 perovskite solar cells (PSCs) because of their higher crystallization temperatures and thermal expansion coefficients. Herein, the interfacial strain is released by fabricating a WS2 /CsPbBr3 van der Waals heterostructure owing to their matched crystal lattice structure and the atomically smooth dangling bond-free surface to act as a lubricant between ETL and CsPbBr3 perovskite. Arising from the strain-released interface and condensed perovskite lattice, the best device achieves an efficiency of 10.65 % with an ultrahigh open-circuit voltage of 1.70 V and significantly improved stability under persistent light irradiation and humidity (80 %) attack over 120 days.

Polymer-induced lattice expansion leads to all-inorganic CsPbBr3 perovskite solar cells with reduced trap density

All-inorganic perovskite materials (CsPbBr3) with long-term stability have been attracted enormous attention for commercialization. Here, a one-step spin-coating method was employed to yield high-purity CsPbBr3 perovskite films. The polyethylene glycol (PEG) was introduced into a precursor solution to balance the nucleation and growth rate. Noticeably, adding a polymeric material of PEG also leaded to a uniform lattice expansion in CsPbBr3 thin layers. The polymer-induced lattice expansion benefits the performances of a CsPbBr3 device due to reduced trap density, boosting the power conversion efficiency. This work emphasizes that controlled lattice expansion benefits in enhancing the electronic functionalities of perovskites.

Size-controlled emission of long-time durable CsPbBr3 perovskite quantum dots embedded tellurite glass nanocomposites

Among various semiconductor quantum dot materials, all-inorganic CsPbBr3 perovskite quantum dots (PQDs) are at the center of ongoing research with their excellent optical properties. However, poor durability of CsPbBr3 PQDs under ambient conditions, e.g. oxygen, heat, moisture, light-exposure, results in keeping them away from long-term practical applications. One of the most promising approaches to improve their durability is the preservation of CsPbBr3 PQDs in oxide glass hosts. Therefore, in this study, CsPbBr3 PQDs are successfully embedded inside a tellurite-based glass via melt-quenching and subsequent heat-treatment. Pure cubic structure of CsPbBr3 PQDs is confirmed by X-ray diffraction analysis. Radii of PQDs are tuned in the range of 2.36–4.89 nm and emission color modulation between 469 and 520 nm with narrow full width at half maximum values of 16–23 nm is realized by band gap tailoring from 3.03 eV to 2.41 eV through rigorous heat-treatment procedures. CsPbBr3 PQDs exhibit superior thermal and chemical durability and impressively stable photoluminescence properties due to strong protection of tellurite glass host. Consequently, excellent long-term durability along with highly pure and tunable emission colors of CsPbBr3 PQDs embedded tellurite glass nanocomposites may lead the way of these outstanding materials through practical photonic and opto-electronic applications.

Exciton recombination mechanisms in solution grown single crystalline CsPbBr3 perovskite

Lead halide perovskites have attracted tremendous attention recently due to their great success in the fields of photovoltaic technologies and light-emitting devices. In this work, the excitonic photoluminescence (PL) properties of all-inorganic perovskite CsPbBr3 were investigated in detail via temperature-dependent PL and Raman spectroscopy in the range of 87 K–297 K, benefiting from our recent work on solution growth of high-quality CsPbBr3 single crystals. The exciton binding energy was extracted as 37 ± 2.7 meV from temperature-dependent PL emission intensity. Furthermore, the PL emission peak energy showed complicated behaviors compared to common semiconductors. With the increase of temperature, the PL emission spectrum blueshifted below 223 K, while it was redshifted in the range of 223 K–293 K. Theoretical research indicated that the thermal expansion governs the energy bandgap evolution of CsPbBr3 below 223 K, while for higher temperatures, the contribution of electron-phonon interaction became dominant. Meanwhile, the broadening of the PL emission spectrum was mainly attributed to the exciton-longitudinal optical phonon scattering. Our results may contribute to a better understanding of the luminescence behaviors in all-inorganic perovskite CsPbBr3-based light-emitting devices in the future.

Ferroelastic Domains in a CsPbBr3 Single Crystal and Their Phase Transition Characteristics: An in Situ TEM Study

The all-inorganic halide perovskite CsPbBr3 has attracted significant attention for applications of high-performance and stable solar cells, light-emitting diodes (LEDs), and photoelectric and X-/γ...