All-inorganic Lead Halide Perovskite Research Articles

Multicolor emission from lanthanide ions doped lead-free Cs3Sb2Cl9 perovskite nanocrystals

The toxicity of lead ions has become the severe challenge for the all-inorganic lead halide perovskite materials, although some works have reported the lead-free perovskite nanocrystals (NCs), the photoluminescence quantum yield (PLQY) of these materials is still unsatisfactory. Meanwhile, because the halogen ions can be easily exchanged, the controllable multicolor emission in perovskite NCs is difficult to realize in current reports. In this work, we introduced lanthanide ions into lead-free Cs3Sb2Cl9 perovskite NCs. Benefitting from the energy transfer between Cs3Sb2Cl9 perovskite NC host and lanthanide ions, the multicolor emission was realized. Based on controlling the doping concentration of Tb3+ and Eu3+ ions, the white light emission under UV excitation would be turned easily in the Tb3+/Eu3+ codoped NCs. In addition, efficient energy transfer from perovskite NCs to Tb3+ or Eu3+ ions is beneficial to improving the optical properties of lead-free perovskite NCs, resulting in maximum PLQYs of red, green and white light emission of 22.6%, 19.7% and 28.5%, respectively. Finally, a white light emitting device (WLED) was fabricated with a power efficiency of 18.5 lm/W, which presents the Commission Internationale de l’Eclairage (CIE) of (0.33, 0.35).

Strongly luminescent and highly stable CsPbBr3/Cs4PbBr6 core/shell nanocrystals and their ultrafast carrier dynamics

All-inorganic lead halide perovskites nanocrystals (NCs) have been demonstrated to be promising candidates for optoelectronic devices, but preparing perovskite NCs with high photoluminescence quantum yields (PLQYs) and excellent stability has been a challenge. In this work, CsPbBr3/Cs4PbBr6 core/shell NCs with a PLQYs of 87.23% and long-term stability in ambient environments was prepared by room temperature inverse microemulsion method. The excellent stability of the sample was attributed to the protection of Cs4PbBr6, and higher PLQYs could be owing to the passivation effect of the core/shell structure. To illustrate the distribution of photogenerated carrier in the core/shell structure, a confined excitons model was proposed based on time-resolved PL and temperature dependent PL measurements. Femtosecond time-resolved transient absorption spectra measurements were performed upon different excitation wavelength to unveil the photogenerated carrier dynamics in core/shell NCs. Upon 300 nm excitation, a carrier transfer process with the time of 3.18 ps from shell to core layer was observed. Furthermore, both two- and three-photon absorption PL was discovered in core/shell NCs, further verifying the carrier transfer process.

Optoelectronic Devices of Large-Scale Transferred All-Inorganic Lead Halide Perovskite Thin Films.

We report the large-scale transfer process for monocrystalline CsPbBr3 thin films prepared by chemical vapor deposition (CVD) with excellent optical properties and stability. The transfer process is robust, simple, and effective, in which CsPbBr3 thin films could be transferred to several substrates and effectively avoid chemical or physical fabrication processes to damage the perovskite surface. Moreover, the transfer process endows CsPbBr3 and substrates with atomically clean and electronically flat interfaces. We utilize this transfer process to realize several optoelectronic devices, including a photonic laser with a threshold of 61 μJ/cm2, a photodetector with a responsivity of 2.4 A/W, and a transistor with a hole mobility of 11.47 cm2 V-1 s-1. High device performances mainly originate from low defects of high-quality single-crystal perovskite and seamless contact between CsPbBr3 and target substrates. The large-scale nondestructive transfer process provides promising opportunities for optoelectronic applications based on monocrystalline perovskites.

TiN Electrode for High-Performance CsPbBr₃ Perovskite Nanocrystal-Based Photodetectors

Solution-processed all-inorganic lead halide perovskites are widely utilized to develop photodetectors (PDs) due to their excellent optoelectronic properties. The low-cost titanium nitride (TiN) electrode not only has better corrosion resistance than Ag electrode but also possesses good conductivity comparable to Au electrode, but the utilization of TiN electrode in perovskite PDs has been rarely reported. Here, based on all-inorganic CsPbBr3 perovskite nanocrystals (NCs) synthesized through the supersaturated recrystallization method, a high-performance metal–semiconductor–metal (MSM)-type PD with a photo-to-dark-current ratio (PDCR) above <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{4}$ </tex-math></inline-formula> and a dynamic range (DR) of 164 dB was demonstrated by employing the low-cost TiN electrode. It indicates that the PD with TiN electrode maintains a dark current as low as that of PD with Au electrode, while that with Ag electrode is hundreds of times inferior. It also reflects that the photocurrent of the PD with TiN electrode is quite close to that of the Au electrode counterpart, which exhibits a 161 times improvement with respect to the PD with Ag electrode. Moreover, the TiN electrode PD demonstrates a much better stability relative to the device with Ag electrode. Our work contributes to developing low-cost, high-performance PDs based on solution-processed semiconductors.

Hybrid Interfacial Engineering: An Enabling Strategy for Highly Sensitive and Stable Perovskite Quantum Dots/Organic Heterojunction Phototransistors

All-inorganic lead halide perovskite quantum dots (PQD) have attracted tremendous research interest in the field of phototransistors due to their excellent optoelectronic properties. However, the inefficient charge transport/extraction and high trap-state density of the assembled PQD films seriously limit the photoresponsivity of PQD-based phototransistors. Herein, we demonstrate that these limits can be overcome by adopting a novel device architecture composed of a polar-polymer capping layer on a PQD/organic semiconductor (OSC) heterojunction. The polar polymer film plays the role of both electron trapping and encapsulation, whereas OSC provides the fast transport tracks for charges and PQD serves as the photoactive materials. Owing to the balanced dynamic processes of photogenerated charges, highly sensitive photodetection is achieved, as demonstrated by the peak photosensitivity of 1.5 × 104, a photoresponsivity of 2.1 × 104 A/W, a detectivity of 1 × 1015 Jones, and a high gain of 6.4 × 104 under weak incident light of 3 μW/cm2. Additionally, the phototransistors exhibit superior stability and reproducibility with negligible changes in the output current both in darkness and under illumination after storing for 4 months. The results demonstrate the promising potentials of the polar polymer/PQD/OSC heterojunction for high-performance photodetectors, and the mechanism and strategy described here can be applied to other kinds of quantum dots-based optoelectronic devices.

3D/2D Core/Shell Perovskite Nanocrystals for High-Performance Solar Cells.

All-inorganic lead halide perovskite nanocrystals (NCs) emerge as a rising star in photovoltaic fields on account of their excellent optoelectronic properties. However, it still remains challenging to further promote photovoltaic efficiency due to the susceptible surface and inevitable vacancies. Here, this work reports a 3D/2D core/shell perovskite heterojunction based on CsPbI3 NCs and its performance in solar cells. The guanidinium (GA+ ) rich 2D nanoshells can significantly passivate surface trap states and lower the capping ligand density, resulting in improved photoelectric properties and carrier transport and diminished nonradiative recombination centers via the hydrogen bonds from amino groups in GA+ ions. Consequently, an outstanding power conversion efficiency (PCE) of up to 15.53% is realized, substantially higher than the control device (13.77%). This work highlights the importance of surface chemistry and offers a feasible avenue to achieve high-performance perovskite NCs-based optoelectronic devices.

Many-Body Correlations and Exciton Complexes in CsPbBr3 Quantum Dots.

All-inorganic lead-halide perovskite (LHP) (CsPbX3 , X=Cl, Br, I) quantum dots (QDs) have emerged as a competitive platform for classical light-emitting devices (in the weak light-matter interaction regime, e.g., LEDs and laser), as well as for devices exploiting strong light-matter interaction at room temperature. Many-body interactions and quantum correlations among photogenerated exciton complexes play an essential role, for example, by determining the laser threshold, the overall brightness of LEDs, and the single-photon purity in quantum light sources. Here, by combining cryogenic single-QD photoluminescence spectroscopy with configuration-interaction (CI) calculations, the size-dependent trion and biexciton binding energies are addressed. Trion binding energies increase from 7to 17meV for QD sizes decreasing from 30to 9nm, while the biexciton binding energies increase from 15to 30meV, respectively. CI calculations quantitatively corroborate the experimental results and suggest that the effective dielectric constant for biexcitons slightly deviates from the one of the single excitons, potentially as a result of coupling to the lattice in the multiexciton regime. The findings here provide a deep insight into the multiexciton properties in all-inorganic LHP QDs, essential for classical and quantum optoelectronic devices.

High stability and strong luminescence CsPbBr3-Cs4PbBr6 thin films for all-inorganic perovskite light-emitting diodes.

All-inorganic lead halide perovskite, characterized by its exceptional optical and electrical properties, is burgeoning as a potential optoelectronic material. However, the standalone CsPbBr3 component encounters several challenges including small exciton binding energy (≈40 meV) and long charge diffusion length, giving rise to low photo-luminescence quantum-yield (PLQY); ion migration leads to instability in device operation, hindering device operation and potential development. To circumvent these limitations, our research endeavors to construct a novel core-shell structure that transforms the continuous [PbX6]4- octahedron into an isolated octahedral structure. We introduce the Cs4PbBr6 phase with 0D structure to passivate the vacancy defects in CsPbBr3, thereby suppressing ion migration and enhancing the luminescence intensity and stability. Our methodology involves fabricating dense CsPbBr3-Cs4PbBr6 composite films using a co-evaporation method, wherein the molar ratio of CsBr and PbBr2 is precisely adjusted. The films are subsequently rapidly annealed under ambient air conditions, and the effects of different annealing temperatures and annealing times on the CsPbBr3-Cs4PbBr6 films were investigated. Our results demonstrate significantly improved stability of the annealed films, with a mere 15% decrease in PL intensity after 100 days of storage under ambient air conditions at 48% relative humidity (RH). Based on this thin film, we fabricated all-inorganic structure Ag/N-Si/CsPbBr3-Cs4PbBr6/NiO/ITO light emitting diodes (LEDs), the devices have a low turn-on voltage VT ∼3 V and under unencapsulated, ambient air conditions, it can operate continuously for 12 hours under DC drive with only 10% attenuation. The results we obtained open up the possibility of designing and developing air-stable perovskite LEDs.

All-inorganic lead halide perovskite nanocrystals applied in advanced display devices.

Advanced display devices are in greater demand due to their large color gamut, high color purity, ultrahigh visual resolution, and small size pixels. All-inorganic lead halide perovskite (AILHP) nanocrystals (NCs) possess inherent advantages such as narrow emission width, saturated color, and flexible integration, and have been developed as functional films, light sources, backlight components, and display panels. However, some drawbacks still restrict the practical application of advanced display devices based on AILHP NCs, including working stability, large-scale synthesis, and cost. In this review, we focus on AILHP NCs, review the recent progress in materials synthesis, stability improvement, patterning techniques, and device application. We also highlight the important role of materials systems in creating advanced display devices, followed by the challenges and opportunities in industrial processes. This review provides beneficial inspiration for the future development of AILHP NCs in colorful and white backlight, as well as high resolution full-color displays.

Anharmonic phonon renormalization and thermoelectric properties of CsPbX3 (X = Cl, Br, and I): first-principles calculations.

Halide perovskites with ultralow thermal conductivity have emerged as promising candidates for thermoelectric materials. We study the lattice dynamics and thermoelectric properties of cubic all-inorganic lead halide perovskites CsPbX3 (X = Cl, Br, and I) through first-principles calculations. Combined with self-consistent phonon theory, we have successfully renormalized the phonon frequency using a quartic anharmonic term, allowing us to accurately reproduce the phonon dispersion of the high-temperature cubic phase of CsPbX3 without any imaginary frequencies. Cubic CsPbX3 exhibit ultralow lattice thermal conductivities (0.61-1.71 Wm-1 K-1) at room temperature. Because of the strong quartic anharmonic renormalization and hardening of the soft modes, the lattice thermal conductivities of cubic CsPbX3 all exhibit weak temperature dependence. Notably, CsPbCl3 exhibits remarkably high thermal conductivity and a long phonon lifetime. This can be attributed to the smallest atomic mean square displacement and the weakest tilting and distortions of PbCl6 octahedra, resulting from the strongest Pb-Cl covalent bonding. Furthermore, the maximum ZT value of 0.63 at 900 K is obtained for the n-type CsPbBr3.

Anion Doping Delays Nonradiative Electron-Hole Recombination in Cs-Based All-Inorganic Perovskites: Time Domain ab Initio Analysis.

Using time-domain density functional theory combined with nonadiabatic (NA) molecular dynamics, we demonstrate that composition engineering of the X-site anions has a strong influence on the nonradiative electron-hole recombination and thermodynamic stability of cesium-based all-inorganic perovskites. Partial substitution of iodine(I) with bromine (Br) and acetate (Ac) anions reduces the NA electron-vibrational coupling by minimizing the overlap between the electron and hole wave functions and suppressing atomic fluctuations. The doping also widens the energy gap to further reduce the NA coupling and to enhance the open-circuit voltage of perovskite solar cells. These factors increase the charge carrier lifetime by an order of magnitude and improve structural stability in the series CsPbI1.88BrAc0.12 > CsPbI2Br > CsPbI3. The fundamental atomistic insights into the influence of anion doping on the photophysical properties of the all-inorganic lead halide perovskites guide the design of efficient optoelectronic materials.

Simultaneous Lattice Engineering and Defect Control via Cadmium Incorporation for High-Performance Inorganic Perovskite Solar Cells.

Doping of all-inorganic lead halide perovskites to enhance their photovoltaic performance and stability has been reported to be effective. Up to now most studies have focused on the doping of elements in to the perovskite lattice. However, most of them cannot be doped into the perovskite lattice and the roles of these dopants are still controversial. Herein,the authors introduce CdI2 as an additive into CsPbI3-x Brx and use it as active layer to fabricate high-performance inorganic perovskite solar cells (PSCs). Cd with a smaller radius than Pb can partially substitute Pb in the perovskite lattice by up to 2 mol%. Meanwhile, the remaining Cd stays on the surface and grain boundaries (GB) of the perovskite film in the form of Cs2 CdI4-x Br-x , which is found to reduce non-radiative recombination. These effects result in prolonged charge carrier lifetime, suppressed defect formation, decreased GBs, and an upward shift of energybands in the Cd-containing film. A champion efficiency of 20.8% is achieved for Cd-incorporated PSCs, together with improved device ambient stability. This work highlights the importance of simultaneous lattice engineering, defectcontrol and atomic-level characterization in achieving high-performance inorganic PSCs with well-defined structure-property relationships.

(Invited) From Bulk to Nanostructured Perovskites

The dimensionality of semiconductors has a crucial role in determining their properties. Recently, metal halide perovskites have been demonstrated with many exciting applications, attracting wide attention to further their development for advanced optoelectronics, such as photovoltaics, photodetectors, light-emitting diodes, and lasers. At length scales down to nanoscale regimes, surface features as well as quantum confinement effects become dominant in regulating the material properties of perovskite materials. In past years, our group focus on the synthesis and characterization of metal halide perovskites with different configurations, ranging from bulk films, microplates, nanosheets, to nanowires. The corresponding physical properties and device applications were also systematically studied based on their widely tunable dimensionality, morphologies, and compositions.Specifically, for perovskite bulk films, surface defects and bulk structural order significantly affect their device performance. Through optimizing processing techniques, self-assembled quasi-2D perovskite films with graded phase distribution were successfully prepared. Gradient type-II band alignments along the out-of-plane direction of perovskites with spontaneous separation of photo-generated electrons and holes are obtained, which is later employed to construct self-powered vertical-structure photodetectors for the first time. Without any driving voltage, the device exhibited impressive performance with the responsivity up to 444 mA/W and ultrashort response time down to 52 µs. In addition, to assess the intrinsic material properties of crystalline perovskites, freestanding MAPbI3 nanosheets and lead-free Cs3Sb2I9 microplates were fabricated by two-step chemical vapor deposition method, in which excellent optoelectronic performance (e.g., responsively of MAPbI3 nanosheet is measured to be 40 A/W) together with ultra-fast response speed (down to 58 µs) and superior thermal stability were obtained.For nanostructured perovskites, understanding the dimensional features and their impact on the materials and devices is becoming increasingly important. Lately, we reported the direct vapor-liquid-solid growth of single-crystalline all-inorganic lead halide perovskite (i.e., CsPbX3; X = Cl, Br, or I) NWs. These NWs exhibited high-performance photodetection with the responsivity exceeding 4489 A/W and detectivity over 7.9 × 1012 Jones toward the visible light regime. Field-effect transistors based on individual CsPbX3 NWs were also fabricated to show the impressive carrier mobility of 3.05 cm2/Vs, being higher than other all-inorganic perovskite devices. Besides, the realization of high-mobility CsPbBr3 NW devices is reported via a simple surface charge transfer doping strategy. After MoO3 decoration and device fabrication, the hole mobility of CsPbBr3/MoO3 core-shell NW device is significantly enhanced to 23.3 cm2/Vs. All these results provide important guidelines for the further improvement of these perovskite nanostructures for practical utilization.

Chemical conversion of electrodeposited PbO2 to the all-inorganic cesium lead halide perovskites CsPbBr3 and CsPbCl3

There is increasing interest in the development of stable, wide bandgap lead halide perovskites for application as photoelectrodes, light emitting diodes and photosensors. In this work, lead dioxide was electrodeposited from an aqueous electrochemical bath and transformed by a two-step chemical conversion process to CsPbI3, CsPbBr3 and CsPbCl3. X-ray diffraction and scanning electron microscopy measurements confirmed the two-step chemical conversion of PbO2 to PbBr2 or PbCl2 followed by their conversion to the all-inorganic lead halide perovskites CsPbBr3 or CsPbCl3. It was found that chemical conversion of PbO2 to PbI2 and then CsPbI3 led to the non-perovskite δ-CsPbI3. This work presents the first example of the chemical transformation of electrodeposited PbO2 to PbBr2 and PbCl2 to form wide bandgap CsPbBr3 and CsPbCl3 perovskites. Absorbance spectroscopy measurements confirmed the optical gap of the wide bandgap CsPbBr3 and CsPbCl3 materials while linear sweep voltammetry measurements demonstrated that CsPbCl3 has a larger electrochemical stability window than CsPbBr3.

Phase Sensitivity of All-Inorganic Lead Halide Perovskite Nanocrystals

Phase Sensitivity of All-Inorganic Lead Halide Perovskite Nanocrystals

Self-powered photodetectors based on CsPbBr3 quantum dots/organic semiconductors/SnO2 heterojunction for weak light detection

All-inorganic lead halide perovskite quantum dots (QDs) show great potential in the development of photodetectors (PDs) due to their excellent photoelectric properties. However, the photoresponse performance of the pure perovskite QDs-based PDs is usually limited by the poor charge transport efficiency of the perovskite QDs films. Here, high-performance self-powered PDs based on perovskite QDs and organic semiconductor PQT-12 (poly(3,3‴-didodecyl quarterthiophene)) are reported. Even in a self-powered mode, the devices can still show stable photoresponse to light signals and achieve excellent photodetection performance, including a detectivity up to 5.8 × 1012 Jones, and Ilight/Idark ratio up to 105. More importantly, the devices exhibit obvious photoresponse to weak light with intensity as low as 3 nW cm−2. To the best of our knowledge, the weak light detection ability of the device is better than most reported PDs based on perovskite QDs. In addition, the devices can be fabricated into flexible PDs with almost unchanged photocurrent under different bending angles. The overall performances of our devices are excellent among the reported self-powered PDs. This method utilized here provides new guides for developing high-performance self-powered PDs based on perovskite QDs for weak light detection.

Vacuum Evaporation of High-Quality CsPbBr3 Thin Films for Efficient Light-Emitting Diodes

The all-inorganic lead halide perovskite has become a very promising optoelectronic material due to its excellent optical and electrical properties. Device performances are currently hindered by crystallinity of the films and environmental stability. Here, we adopted dual-source co-evaporation method to prepare CsPbBr3 films. By adjusting and controlling the co-evaporation ratio and substrate temperature, we obtained CsPbBr3 films with large grain sizes and uniform morphology. Films with smooth surfaces and large grains exhibit properties such as efficient photon capture, fast carrier transport, and suppressed ion migration. Therefore, in this paper, by refining the annealing conditions, the effects of annealing temperature and time on the films were studied in detail. The CsPbBr3 films were annealed under suitable annealing temperature and time in ambient air, and films with high quality and crystallinity and average grain size up to ~ 2.5 μm could maintain stability in ambient air for 130 days. The corresponding LEDs show the full width at half maximum (FWHM) of the green EL spectrum is as narrow as 18 nm, and the devices have a low turn-on voltage VT ~ 3 V and can work continuously for 12 h in ambient air.

First-Principles Survey of Acceptor Dopants for p-Type Cesium Lead Bromide

All-inorganic lead halide perovskites such as cesium lead bromide (CsPbBr3) are high-performance light emitters with applications in lighting, displays, and quantum information. However, it has proven difficult to achieve high p-type carrier concentrations in these materials. In this work, a wide variety of possible acceptor dopants are evaluated using first-principles calculations. Connecting the results with previous work on native defects, we show that p-type doping is difficult because of two related effects: the moderately high formation energies of acceptor impurities and compensation from native defects, particularly lead–cesium antisites and bromine interstitials. Sodium and silver are identified as the most promising dopants for overcoming these challenges, and optimum chemical potential conditions for acceptor doping are identified.

Solvent‐Mediated Structural Evolution in Colloidal Lead Halide Perovskite Nanocrystals Self‐Assembly (Adv. Mater. Interfaces 19/2022)

Solvent-Mediated Evolution of Colloidal Lead Halide Perovskite Nanocrystals In article number 2200187, Linqi Chen, Hongxing Dong, Long Zhang, and co-workers demonstrate a molecular scale mechanism of solvent-mediated evolution of all-inorganic lead halide perovskite nanocrystals (NCs). By affecting the intermolecular forces between aliphatic ligands on adjacent NCs and regulating the competition between complex bond energy in colloidal NCs system, solvent molecules regulate the self-assembly of ligand-stabilized perovskite NCs and NC arrays and nanowires are freely obtained.

Recent Progress in Lanthanide-Doped Inorganic Perovskite Nanocrystals and Nanoheterostructures: A Future Vision of Bioimaging

All-inorganic lead halide perovskite nanocrystals have great potential in optoelectronics and photovoltaics. However, their biological applications have not been explored much owing to their poor stability and shallow penetration depth of ultraviolet (UV) excitation light into tissues. Interestingly, the combination of all-inorganic halide perovskite nanocrystals (IHP NCs) with nanoparticles consisting of lanthanide-doped matrix (Ln NPs, such as NaYF4:Yb,Er NPs) is stable, near-infrared (NIR) excitable and emission tuneable (up-shifting emission), all of them desirable properties for biological applications. In addition, luminescence in inorganic perovskite nanomaterials has recently been sensitized via lanthanide doping. In this review, we discuss the progress of various Ln-doped all-inorganic halide perovskites (LnIHP). The unique properties of nanoheterostructures based on the interaction between IHP NCs and Ln NPs as well as those of LnIHP NCs are also detailed. Moreover, a systematic discussion of basic principles and mechanisms as well as of the recent advancements in bio-imaging based on these materials are presented. Finally, the challenges and future perspectives of bio-imaging based on NIR-triggered sensitized luminescence of IHP NCs are discussed.