All-Inorganic CsPbBr3 Perovskite Films Prepared by Single Source Thermal Ablation

Advances and Challenges in Large-Area Perovskite Light-Emitting Diodes

Metal halide perovskite light-emitting diodes (PeLEDs) have shown promise for high-definition displays and flat-panel lighting because of their wide color gamut, narrow emission band, and high brightness. The external quantum efficiency of PeLEDs increased rapidly from ≈1% to more than 25% in the past few years. However, most of these high-performance devices are fabricated using a spin coating method with a small device area of <0.1 cm2, limiting their commercial applications. Recently, large-area PeLEDs have attracted growing attention and significant breakthroughs have been reported. This perspective first introduces the pros and cons of each technique in making large-area PeLEDs. The advances in the fabrication of large-area PeLEDs are then summarized using spin coating and mass-production methods such as inkjet printing, blade coating, and thermal evaporation. Moreover, the challenging issues will be discussed that are urgent to be solved for large-area PeLEDs.

High brightness and low operating voltage CsPbBr3 perovskite LEDs by single-source vapor deposition

In this work, we utilized CsPbBr3 powder as the precursor material for the single-source vapor deposition (SSVD) process to fabricate the CsPbBr3 emitting layer. Due to the high density of grain boundaries and defects in the thin films deposited in the initial stages, non-radiative recombination can occur, reducing the efficiency of perovskite light-emitting diodes (PeLED). To address this issue, we employed a thermal annealing process by subjecting the perovskite films to the appropriate annealing temperature, facilitating the coalescence and growth of different grains, improving lattice integrity, and thereby reducing the presence of defects and enhancing the photoluminescence performance of the films. Furthermore, in this study, we successfully fabricated simple-structured CsPbBr3 PeLED using thermally annealed CsPbBr3 films. Among these components, even without adding the electron and hole transport layers, the best-performing device achieved a maximum brightness of 14,079 cd/m2 at a driving voltage of only 2.92 V after annealing at 350 °C; the brightness is 16.8 times higher than that of CsPbBr3 PeLED without heat treatment, demonstrating outstanding light-emitting performance. The research results show that using SSVD to prepare CsPbBr3 PeLED has broad application potential, providing a simple process option for research on improving the performance of PeLED.

Simple and sustainable synthesis of perovskite-based optoelectronic material: CsPbBr3 nanocrystals via laser ablation in alcohol

All-inorganic lead halide perovskite nanocrystals (NCs) have shown great potential as emerging semiconducting materials due to their excellent optoelectronic properties. However, syntheses in solution commonly use high temperatures and toxic solvents, which are obstacles for safety and sustainability of the process. In this work, laser ablation in alcohol is proposed as a simple and sustainable, ligand-free, top-down approach to synthesize CsPbBr3 nanocrystals in ambient conditions. The effects of different low boiling point commercial alcohols used as solvents on the optical properties of CsPbBr3 NCs colloidal solutions are investigated. Although in traditional bottom-up synthesis alcohols are usually found to be not appropriate for the synthesis of perovskite NCs, here it is demonstrated that CsPbBr3 orthorhombic nanocrystals with narrow full width half maximum (FWHM < 18 nm), long photoluminescence lifetimes (up to 17.9 ns) and good photoluminescence quantum yield (PLQY up to 15.5%) can be obtained by selecting the dielectric constant and polarity of the alcohol employed for the synthesis.

A Review of Recent Developments in Preparation Methods for Large-Area Perovskite Solar Cells

The recent rapid development in perovskite solar cells (PSCs) has led to significant research interest due to their notable photovoltaic performance, currently exceeding 25% power conversion efficiency for small-area PSCs. The materials used to fabricate PSCs dominate the current photovoltaic market, especially with the rapid increase in efficiency and performance. The present work reviews recent developments in PSCs’ preparation and fabrication methods, the associated advantages and disadvantages, and methods for improving the efficiency of large-area perovskite films for commercial application. The work is structured in three parts. First is a brief overview of large-area PSCs, followed by a discussion of the preparation methods and methods to improve PSC efficiency, quality, and stability. Envisioned future perspectives on the synthesis and commercialization of large-area PSCs are discussed last. Most of the growth in commercial PSC applications is likely to be in building integrated photovoltaics and electric vehicle battery charging solutions. This review concludes that blade coating, slot-die coating, and ink-jet printing carry the highest potential for the scalable manufacture of large-area PSCs with moderate-to-high PCEs. More research and development are key to improving PSC stability and, in the long-term, closing the chasm in lifespan between PSCs and conventional photovoltaic cells.

Performance-Improved Highly Integrated Uniaxial Tristate Hybrid Nanogenerator for Sustainable Mechanical Energy Harvesting

Despite advances in the development of individual nanogenerators, the level of output energy generation must be increased to meet the demands of commercial electronic systems and to broaden their scope of application. To harvest low-frequency ambient mechanical energy more efficiently, we proposed a highly integrated hybridized piezoelectric-triboelectric-electromagnetic (tristate) nanogenerator in a uniaxial structure. In its highly integrated approach, a piezoelectric nanogenerator (PENG) based on CsPbBr₃ (cesium lead bromide) nanoparticles (NPs) and poly(dimethylsiloxane) (PDMS) nanocomposite was fabricated on a triboelectrically negative nanostructured polyimide (PI) substrate. A cylindrical aluminum electrode grooved with permanent magnets was directed to move along a spring-less metallic guide bounded by these nanocomposites, thus essentially forming two single-electrode mode triboelectric nanogenerators (TENGs). By its optimized material design and novel integration approach of the PENGs, TENGs, and electromagnetic generators (EMGs), this uniaxial tristate hybrid nanogenerator (UTHNG) can synergistically produce an instantaneous electrical power of 49 mW at low-frequency ambient vibration (5 Hz). The UTHNG has excellent charging characteristics, ramping up the output voltage of a 22 μF capacitor to 2.7 V in only 12 s, which is much faster than individual nanogenerators. This work will be a superior solution for harvesting low-frequency ambient energies by improving the performance of hybrid nanogenerators, potentially curtailing the technology gap for self-powered micro/nanosystems for the Internet of Things.

Hole Transport Layer Free Perovskite Light-Emitting Diodes With High-Brightness and Air-Stability Based on Solution-Processed CsPbBr3-Cs4PbBr6 Composites Films

Recently, perovskite light-emitting diodes (PeLEDs) have drew widespread attention due to their high efficiencies. However, because of the sensitivity to moisture and oxygen, perovskite luminescent layers are usually prepared in high-purity nitrogen environment, which increases the cost and process complexity of device preparation and seriously hindrances its commercialization of PeLED in lighting and display application. Herein, dual-phase all-inorganic composite CsPbBr₃-Cs₄PbBr₆ films are fabricated from CsBr-rich perovskite solutions by a simple one-step spin-coating method in the air with high humidity. Compared with the pure CsPbBr₃ film, the composite CsPbBr₃-Cs₄PbBr₆ film has much stronger photoluminescence emission and longer fluorescence lifetime, accompanied by increased photoluminescence quantum yield (33%). As a result, we obtained green PeLED devices without hole transport layer exhibiting a maximum brightness of 72,082 cd/m² and a maximum external quantum efficiency of about 2.45%, respectively. More importantly, the champion device shows excellent stability with operational half-lifetime exceeding 1,000 min under continuous operation in the air. The dual-phase all-inorganic composite CsPbBr₃-Cs₄PbBr₆ film shows attractive prospect for advanced light emission applications.

Pulsed Laser Deposition of CsPbBr3 Films: Impact of the Composition of the Target and Mass Distribution in the Plasma Plume

All-inorganic cesium lead bromine (CsPbBr3) perovskites have gained a tremendous potential in optoelectronics due to interesting photophysical properties and much better stability than the hybrid counterparts. Although pulsed laser deposition (PLD) is a promising alternative to solvent-based and/or thermal deposition approaches due to its versatility in depositing multi-elemental materials, deep understanding of the implications of both target composition and PLD mechanisms on the properties of CsPbBr3 films is still missing. In this paper, we deal with thermally assisted preparation of mechano-chemically synthesized CsPbBr3 ablation targets to grow CsPbBr3 films by PLD at the fluence 2 J/cm2. We study both Cs rich- and stoichiometric PbBr2-CsBr mixture-based ablation targets and point out compositional deviations of the associated films resulting from the mass distribution of the PLD-generated plasma plume. Contrary to the conventional meaning that PLD guarantees congruent elemental transfer from the target to the substrate, our study demonstrates cation off-stoichiometry of PLD-grown CsPbBr3 films depending on composition and thermal treatment of the ablation target. The implications of the observed enrichment in the heavier element (Pb) and deficiency in the lighter element (Br) of the PLD-grown films are discussed in terms of optical response and with the perspective of providing operative guidelines and future PLD-deposition strategies of inorganic perovskites.

Electronic and optical properties of bulk and surface of CsPbBr3 inorganic halide perovskite a first principles DFT 1/2 approach

This work aims to test the effectiveness of newly developed DFT-1/2 functional in calculating the electronic and optical properties of inorganic lead halide perovskites CsPbBr3. Herein, from DFT-1/2 we have obtained the direct band gap of 2.36 eV and 3.82 eV for orthorhombic bulk and 001-surface, respectively. The calculated energy band gap is in qualitative agreement with the experimental findings. The bandgap of ultra-thin film of CsPbBr3 is found to be 3.82 eV, which is more than the expected range 1.23-3.10 eV. However, we have found that the bandgap can be reduced by increasing the surface thickness. Thus, the system under investigation looks promising for optoelectronic and photocatalysis applications, due to the bandgap matching and high optical absorption in UV-Vis (Ultra violet and visible spectrum) range of electro-magnetic(em) radiation.