Single-source Evaporation Research Articles

Perovskite Light-Emitting Diode Display Based on MoS2 Backplane Thin-Film Transistors.

The uniform deposition of perovskite light-emitting diodes (PeLEDs) and their integration with backplane thin-film transistors (TFTs) remain challenging for large-area display applications. Herein, an active-matrix PeLED display fabricated via the heterogeneous integration of cesium lead bromide LEDs and molybdenum disulfide (MoS2 )-based TFTs is presented. The single-source evaporation method enables the deposition of highly uniform perovskite thin films over large areas. PeLEDs are integrated with MoS2 TFTs to fabricate an active-matrix PeLED display with an 8 × 8 array, which exhibits excellent brightness control capability and high switching speed. This study demonstrates the potential of PeLEDs as candidates for next-generation displays and presents a novel approach for fabricating optoelectronic devices via the heterogeneous integration of 2D materials and perovskites, thereby paving the way toward the fabrication of practical future optoelectronic systems.

Substoichiometric Mixing of Metal Halide Powders and Their Single-Source Evaporation for Perovskite Photovoltaics

Substoichiometric Mixing of Metal Halide Powders and Their Single-Source Evaporation for Perovskite Photovoltaics

Enhancing Photovoltaic Performance and Stability of Perovskite Solar Cells through Single-Source Evaporation and CsPbBr3 Quantum Dots Incorporation

This study investigates the potential of inorganic perovskite CsPbBr3 as a photovoltaic material, highlighting its superior stability compared to that of organic–inorganic hybrid perovskite materials. Conventional methods for preparing CsPbBr3 perovskite films, such as the two-step method and the dual-source thermal evaporation method, face challenges in obtaining high-purity films due to the decomposition of precursor films and the formation of multiple heterogeneous phases. To address this issue, we synthesized CsPbBr3 powder material using thermal evaporation deposition, which effectively suppressed decomposition and the formation of heterogeneous phases. Consequently, we achieved uniform and dense CsPbBr3 perovskite films. By incorporating energy-band engineering modification with CsPbBr3 quantum dots (QDs), the all-inorganic perovskite solar cells (PSCs) attained a power conversion efficiency (PCE) of 7.01% under standard solar illumination conditions. The device PCE remained at 93% of its initial efficiency under 30% relative humidity conditions for over 100 days, showcasing its durability. The developed method produced an average grain size of 800 nm, resulting in a smooth and uniform film surface, thereby demonstrating the method’s high repeatability. Additionally, the optimized PSCs exhibited a high open-circuit voltage (VOC) with the champion device reaching a VOC of 1.38 V and a PCE of 7.01%. This research presents a robust, efficient, and cost-effective approach for fabricating high-quality all-inorganic PSCs.

Structural and photo physical investigation of single-source evaporation of CsFAPbI3 and FAPbI3 perovskite thin films

Structural and photo physical investigation of single-source evaporation of CsFAPbI3 and FAPbI3 perovskite thin films

Single‐source evaporation of CH 3 NH 3 SnI 3 for Pb‐free perovskite solar cells

Sn-based perovskite is the most promising candidate as environmentally benign and Pb-free perovskite; however, the nonuniform morphology of Sn-based perovskite thin films caused by rapid crystallization is a major issue. We demonstrate how pure CH3NH3SnI3 (CH3NH3 = methylammonium, MA) thin films can be uniformly deposited by the single-source evaporation of presynthesized MASnI3 crystals. The perovskite crystals are synthesized by cooling crystallization under an ambient atmosphere and sublimed without decomposition by controlling the heating rate. The evaporated thin films were postannealed at various temperatures and times, which resulted in a pinhole-free microstructure with an average grain size of 423 nm. The average power conversion efficiency (PCE) of planar-type solar cells based on the optimized perovskite thin films was 1.7% ± 0.1%.

Structural and photophysical investigation of single-source evaporation of CsFAPbI3 and FAPbI3 perovskite thin films

Single source vacuum deposition is a stimulating technique for upscaling perovskite solar cells.

The influence of posttreatment processes on the structures and the optical and electrical properties of CuInS2 and its heterojunction with various sulfides (CdS, CdZnS, and CdCuS)

As the first essential step toward understanding how to obtain an efficient CuInS2-based solar cell, this paper studied the photoelectric properties of CuInS2 and sulfide P–N heterojunction. For this purpose, the single-source evaporation method and the chemical bath deposition had been applied to prepare CuInS2 films and sulfide films (CdS, CdZnS, and CdCuS), respectively. The powder source was obtained from CuInS2 polycrystalline ingot, which consists of CuInS2 chalcopyrite phase. The segregated CuxS secondary phase on the surfaces of CuInS2 films could be removed by etching of bromine–methanol (BM) solution. The structures of ternary sulfide films (CdZnS and CdCuS) were similar to that of CdS film. The transient photocurrent of CdZnS thin film was highest, which might be related to the high reaction activity and the good crystal quality. Furthermore, the I–V response of CuInS2 and CdZnS heterojunction was studied, which was close to the ideal diode type behavior. The low reverse saturation current density, the optimal diode ideality factor, and the high barrier height were obtained from the I–V curve of CuInS2 and CdZnS heterojunction, which might mean that the CdZnS film could be suitable to use in photovoltaic application.

Enhancement of the thermoelectric properties of Bi2Te3 nanocrystal thin films by rapid annealing

In this work, stoichiometric Bi2Te3 thin films were successfully prepared on a polymer substrate by using single-source evaporation method. Rapid annealing was applied to improve the crystallinity and control the grain size of the thin films, thereby conferring them with high thermoelectric performance. As expected, the prepared thin films revealed a pure Bi2Te3 phase with nanosized grains. Consequently, a substantially enhanced power factor and reduced lattice conductivities resulting in a high ZT value of 0.5 was achieved. The results of the present work provide novel insights into the development of high-performance thermoelectric thin films through thermal control of crystallinity and grain size.

Single-Source Vapor-Deposited Cs2AgBiBr6 Thin Films for Lead-Free Perovskite Solar Cells.

Lead-free double perovskites have been considered as a potential environmentally friendly photovoltaic material for substituting the hybrid lead halide perovskites due to their high stability and nontoxicity. Here, lead-free double perovskite Cs2AgBiBr6 films are initially fabricated by single-source evaporation deposition under high vacuum condition. X-ray diffraction and scanning electron microscopy characterization show that the high crystallinity, flat, and pinhole-free double perovskite Cs2AgBiBr6 films were obtained after post-annealing at 300 °C for 15 min. By changing the annealing temperature, annealing time, and film thickness, perovskite Cs2AgBiBr6 solar cells with planar heterojunction structure of FTO/TiO2/Cs2AgBiBr6/Spiro-OMeTAD/Ag achieve an encouraging power conversion efficiency of 0.70%. Our preliminary work opens a feasible approach for preparing high-quality double perovskite Cs2AgBiBr6 films wielding considerable potential for photovoltaic application.

Efficient Inorganic Cesium Lead Mixed‐Halide Perovskite Solar Cells Prepared by Flash‐Evaporation Printing

A single source evaporation method, named flash-evaporation printing, using a laser as the heating source and carbon nanotube sheets as the evaporator, is applied to deposit inorganic perovskite films. Compact and uniform perovskite films can be obtained, contributing to efficient large area solar cells. More details can be found in article number 1800986 by, Yang Wei, Kaili Jiang, Hong Lin, and co-workers.

High-Quality Perovskite CH₃NH₃PbI₃ Thin Films for Solar Cells Prepared by Single-Source Thermal Evaporation Combined with Solvent Treatment.

In this work, solvent annealing process for CH3NH3PbI3 thin film prepared by single source evaporation was reported. Characterized by the scanning electron microscope (SEM), X-ray diffractometer (XRD), energy dispersive spectroscope (EDS), ultraviolet-visible (UV) spectrophotometer, and the photoluminescence (PL) spectrometer, our method ensured higher quality film with crystallinity, composition, well-defined grain structure, and reproducibility. The optimized solar cell device based on the structure of ITO/PEDOT:PSS/CH3NH3PbI3/PCBM/Ag achieved better performance in power conversion efficiency from 2.64% to 9.92%, providing an effective method to optimize the quality of perovskite film for solar cell application.

Efficient Inorganic Cesium Lead Mixed‐Halide Perovskite Solar Cells Prepared by Flash‐Evaporation Printing

Cesium‐based inorganic perovskites have attracted enormous interest for efficient and stable photovoltaics, while still a few studies apply evaporation methods with high reproducibility to prepare them. Herein, high‐quality CsPbI2Br films are deposited by flash‐evaporation printing (FEP), a single source evaporation method using laser as the heating source and carbon nanotube sheets as the evaporator. Uniform films with balanced stoichiometry and high crystallinity can be obtained by controlling the precursor ratio and post‐annealing conditions. Planar solar cells using these inorganic perovskite films exhibit champion power conversion efficiencies of 12.2% in small areas (0.06 cm2) and 9.4% in large areas (1 cm2) with insignificant hysteresis, indicating that the FEP method is a promising way in preparing high‐quality inorganic perovskite films for efficient large‐area devices.

Laser-Induced Flash-Evaporation Printing CH3NH3PbI3 Thin Films for High-Performance Planar Solar Cells.

Organic-inorganic hybrid perovskites have been emerging as promising light-harvesting materials for high-efficiency solar cells recently. Compared to solution-based methods, vapor-based deposition technologies are more suitable in preparing compact, uniform, and large-scale perovskite thin films. Here, we utilized flash-evaporation printing (FEP), a laser-induced ultrafast single source evaporation method employing a carbon nanotube evaporator, to fabricate high-quality methylammonium lead iodide perovskite thin films. Stoichiometric films with pure tetragonal perovskite phase can be achieved using a controlled methylammonium iodide to lead iodide ratio in evaporation precursors. The film crystallinity and crystal grain growth could further be promoted after postannealing. Planar solar cells (0.06 cm2) employing these perovskite films exhibit a champion power conversion efficiency (PCE) of 16.8% with insignificant hysteresis, which is among the highest reported PCEs using vapor-based deposition methods. Large-area (1 cm2) devices based on such perovskite films also achieved a stabilized PCE of 11.2%, indicating the feasibility and scalability of our FEP method in fabricating large-area perovskite films for other optoelectronic applications.

Deposition routes of Cs2AgBiBr6 double perovskites for photovoltaic applications

ABSTRACTThe lead free double perovskite Cs2AgBiBr6 is an upcoming alternative to lead based perovskites as absorber material in perovskite solar cells. So far, the majority of investigations on this interesting material have focused on polycrystalline powders and single crystals. We present vapor and solution based approaches for the preparation of Cs2AgBiBr6 thin films. Sequential vapor deposition processes starting from different precursors are shown and their weaknesses are discussed. Single source evaporation of Cs2AgBiBr6 and sequential deposition of Cs3Bi2Br9 and AgBr result in the formation of the double perovskite phase. Additionally, we show the possibility of the preparation of planar Cs2AgBiBr6 thin films by spin coating.

Preparation and Characterization of Cu2ZnSn(S x Se1−x )4 Thin Films by Synchronous Sulfo-Selenization of Single-Source Evaporated Metallic Precursors

Cu2ZnSn(S,Se)4 (CZTSSe) thin film was prepared using a simple two-step approach based on the single-source evaporation and synchronous sulfo-selenization. Composition, microstructure, morphology, and properties of the as-prepared CZTSSe thin films were investigated. XRD and Raman patterns confirmed the formation of single-phase CZTSSe solid solutions. SEM results showed that the CZTSSe thin film had a uniform morphology and large grains. EDS results revealed the composition of CZTSSe film was Cu:Zn:Sn:S:Se = 23.7:12.6:12.2:37.7:13.8 (in at%), which was in accordance with the stoichiometric Cu2ZnSn(S,Se)4. The optical band gap of CZTSSe thin film evaluated from its UV–Vis spectrum was 1.33 eV. The resistivity, carrier concentration, and mobility were 0.53 Ω cm, 7.9 × 1018 cm3, and 7.5 cm2/(Vs), respectively.

Influence of annealing temperature on the phase composition and optical properties of CuInS2 films

We studied the growth of CuInS2 thin films by single-source evaporation of CuInS2 powder in a high-vacuum system with a base pressure of 10−3Pa. After evaporation, the films were annealed in a sulfur atmosphere at temperatures from 200 to 500°C for 1h. XRD curves and Raman spectra of the films demonstrated that chalcopyrite CuInS2 was the major crystalline phase. The morphology of CuxS exhibited a star-like structure, which we report for the first time. The phase composition and optical properties of our polycrystalline thin films were effectively modified by annealing in S. For films annealed at 200 and 350°C, a secondary CuIn11S17 phase appeared, which may be related to solid-state reaction in the S atmosphere. This secondary CuIn11S17 phase has not been widely reported in previous studies. After annealing at 500°C, only a chalcopyrite phase was detected, with bandgap energy of 1.46eV, which is nearly identical to the optimal bandgap energy (1.5eV) of single-crystal CuInS2. This indicates that the composition of the CuInS2 film annealed at 500°C was nearly stoichiometric. The bandgap of the samples first increased and then decreased with increasing annealing temperature, which may be attributed to an increase in grain size, the secondary CuIn11S17 phase, and deviation from stoichiometry.

Organic charge transfer phase formation in thin films of the BEDT-TTF/TCNQ donor–acceptor system

We have performed charge transfer phase formation studies on the donor/acceptor system bis-(ethylendithio)tetrathiafulvalene (BEDT-TTF)/tetracyanoquinodimethane,(TCNQ) by means of physical vapor deposition. We prepared donor/acceptor bilayer structures on glass and Si(100)/SiO 2 substrates held at room temperature and analyzed the layer structures by optical microscopy, X-ray diffraction and focused ion beam cross sectioning before and after annealing. We found clear evidence for the formation of a charge transfer phase during the annealing procedure. For the as-grown samples we could not detect the occurrence of a charge transfer phase. X-ray diffraction indicated that the monoclinic variant of the (BEDT-TTF)-TCNQ was formed. This was further corroborated by single-source evaporation experiments from pre-reacted (BEDT-TTF)-TCNQ obtained from solution growth, and in particular from co-evaporation experiments of (BEDT-TTF)-TCNQ and TCNQ. In the course of these experiments we found that (0 ℓℓ)-oriented BEDT-TTF layers can be prepared on α-Al 2O 3 (112̄0) substrates at about 100 °C using (BEDT-TTF)-TCNQ as source material. We speculate that due to its high vapor pressure the TCNQ component serves as a carrier gas for BEDT-TTF vapor phase transport.

Studies on structural, electrical, and optical properties of Cu doped As–Se–Te chalcogenide glasses

Cu doped chalcogenide (ChG) glassy films in the As–Se–Te glass system have been prepared using thermal evaporation techniques. Single-source evaporation from bulk (1−x) As0.40Se0.35Te0.25+x Cu glasses with x=0.05, 0.075, 0.10, 0.125, and 0.15, as well as dual-source coevaporation from As-chalcogenide and Cu-chalcogenide binary glasses as source materials, has been explored. We have shown that it is not possible to deposit high concentration Cu doped ChG glassy films, from the Cu doped bulk samples using single-source evaporation. However, using the dual-source coevaporation technique, we have demonstrated that the films can be doped with high concentrations of Cu. Micro-Raman spectroscopy has been utilized to verify that Cu is introduced into the glass network without disrupting the basic As-chalcogen units. Optical measurements have shown that introduction of Cu decreases the band gap of As–Se–Te glasses. The electrical properties of the investigated films have been measured at different temperatures and it has been shown that Cu incorporation in the As–Se–Te glass system vastly improves electrical conductivity. Moreover, we have shown that the temperature dependence of electrical conductivity can be fitted assuming variable range hopping between states near the Fermi level.

Electrical and luminescent properties of CuGaSe 2 crystals and thin films

CuGaSe 2 thin films with thicknesses of about 2 μm were prepared by flash and single source evaporation onto mica and (1 1 0)-oriented ZnSe substrates in the substrate temperature range 150–450°C. The obtained polycrystalline CuGaSe 2 films had the chalcopyrite structure with the predominant growth direction 〈2 2 1〉. Hall effect, conductivity and luminescence measurements have been carried out on CuGaSe 2 thin films and source materials: CuGaSe 2 single crystals grown by Bridgman technique and by chemical vapour transport using I 2 as transport agent. All films and crystals are p-type. Two acceptor levels with ionization energies E A1∼50–56 meV and E A2∼130–150 meV have been identified as due to Ga vacancy and presence of Se atoms on interstitial sites respectively.

Molybdenum Diffusion in CuInSe2 Thin Films

Molybdenum diffusion in CuInSe2 (CIS) films was investigated in the temperature range 240-520°C using the energy-dispersive X-ray (EDX) and resistivity techniques. CuInSe2 thin films were deposited by single-source evaporation on glass and molybdenum-covered glass substrates. The temperature dependence of Mo diffusion coefficient is described by equation D=1.3×10-8exp (-0.53/kT). It is shown that the diffusion doping of p-type CIS by molybdenum is accompanied by the significant decrease of resistivity. The observed results of the diffusion and electrical measurements are attributed to migration of Mo in the polycrystalline CIS films by means of both along intergrain surfaces and into grains.