One-step Spin-coating Research Articles

Low-voltage operating, high mobility top-gate structural flexible organic thin-film transistor with a one-step spin-coated binary polymer gate dielectric

Low-voltage operation is one of the prerequisites for the practical applications of the organic thin-film transistors (OTFTs). Up to date, the most reported low-voltage operatable OTFTs use a bottom-gate structure, and are fabricated by several different technologies in the whole process, in which the organic semiconductors and/or gate dielectrics are prepared in the expensive vacuum equipment. The simple fabricating technologies and fewer processes can better demonstrate the inherent advantages, and enhance the commercial competitiveness of OTFTs. Here, we propose a strategy to fabricate the binary polymers gate dielectric by one-step spin-coating in the top-gate structured flexible OTFTs, by which not only the device performances are prominently improved, but also the fabricating process of the OTFTs is minimized. As a result, the flexible OTFTs exhibit a high mobility over 0.5 cm2 Vs−1, low threshold voltage near to −0.5 V, and excellent mechanical bending durability with a very slightly performances degradation after the tensile and compressive bending at a small curvature radius of 3.0 mm over 1000 cycles.

Additive-regulated one-step dynamic spin-coating for fabricating high-performance perovskite solar cells under high humidity conditions

Perovskite films fabricated using a one-step dynamic spin-coating process under high humidity conditions (45–55% RH).

One-step spin-coating of methylammonium lead iodide on SILAR-deposited tin oxide, SnO2 films for effective electron transport

Tin oxide (SnO2) materials were prepared via successive ionic layer adsorption and reaction (SILAR) technique at varying deposition times. The synthesized tin oxide layer served as an electron transport layer for the deposition of a perovskite layer via spin coating method. The morphology, structure, elemental, optical features and vibration modes of the prepared samples have been studied using scanning electron microscopy (SEM), X-ray diffractometry (XRD), energy dispersive X-ray spectroscopy (EDX), UV–vis spectrophotometry, and Raman spectrophotometry, respectively. The films revealed granular-shaped nanograins with a maximum average grain size of 197.03 nm. XRD results showed a cassiterite pure-phase crystal structure with several prominent peaks. EDX studies confirmed the as-deposited elemental constituents with good optical properties obtained from the optical studies. The band gap energies ranged from 4.01 to 4.24 eV at increasing deposition times. The phonon modes and crystal structures were also revealed from the Raman studies. The materials find applications in solar cells and electronic devices.

High-Efficiency CsPbBr3 Light-Emitting Diodes using One-Step Spin-Coating In Situ Dynamic Thermal Crystallization.

All-inorganic perovskite materials (such as CsPbBr3) have received widespread attention because of their better stability than hybrid counterparts, but their poor film morphology and crystalline quality limit their application in perovskite light-emitting devices (PeLEDs). Some previous studies have attempted to improve the morphology and crystalline quality of perovskite films by heating the substrate, but there are still some problems such as inaccurate temperature control, excessive temperature is not conducive to flexible applications, and the mechanism of action is not clear. In this work, we used a one-step spin-coating, low-temperature in situ thermally assisted crystallization process, in which the temperature was accurately monitored using a thermocouple in the range of 23-80 °C, and explored the effect of the in situ thermally assisted crystallization temperature on the crystallization of the all-inorganic perovskite material CsPbBr3 and the performance of PeLEDs. In addition, we focused on the influence mechanism for the in situ thermally assisted crystallization process on the surface morphology and phase composition of the perovskite films and promote its possible application in inkjet printing and scratch coating methods.

Synthesis of Cs+-Tuned (PEA)2PbI4 Perovskite Thin Films by One-Step Spin Coating

As a candidate material for the next generation photovoltaic and light-emitting devices, organic-inorganic hybrid perovskite materials have attracted extensive attention. In this study, a (PEA)2PbI4 hybrid perovskite film was prepared by a one-step spin-coating method at room temperature. Based on the synthesis of (PEA)2PbI4, the inorganic Cs+ ions were doped in the film to investigate the influence of Cs+ doping on the structure and properties of two-dimensional (2D) perovskite film. The results show that both as-grown (PEA)2PbI4 film and Cs+-doped (PEA)2PbI4 film exhibit the instinct of the layered structure, though excess Cs+ ions doping would make the structure weakened. Through analyzing the optical properties, it is found that, besides the 2D (PEA)2PbI4 phase, a quasi-2D structure with two layers of [PbI6]4−-octahedron forms in Cs+-doped (PEA)2PbI4 perovskite films, which is ascribed to the phase rearrangement of the (PEA)2PbI4 crystal structure under the induction of Cs+ ions.

Water-Processed Ultrathin Crystalline Indium-Boron-Oxide Channel for High-Performance Thin-Film Transistor Applications.

Thin-film transistors (TFTs) made of solution-processable transparent metal oxide semiconductors show great potential for use in emerging large-scale optoelectronics. However, current solution-processed metal oxide TFTs still suffer from relatively poor device performance, hindering their further advancement. In this work, we create a novel ultrathin crystalline indium–boron–oxide (In-B-O) channel layer for high-performance TFTs. We show that high-quality ultrathin (~10 nm) crystalline In-B-O with an atomically smooth nature (RMS: ~0.15 nm) could be grown from an aqueous solution via facile one-step spin-coating. The impacts of B doping on the physical, chemical and electrical properties of the In2O3 film are systematically investigated. The results show that B has large metal–oxide bond dissociation energy and high Lewis acid strength, which can suppress oxygen vacancy-/hydroxyl-related defects and alleviate dopant-induced carrier scattering, resulting in electrical performance improvement. The optimized In-B-O (10% B) TFTs based on SiO2/Si substrate demonstrate a mobility of ~8 cm2/(V s), an on/off current ratio of ~106 and a subthreshold swing of 0.86 V/dec. Furthermore, by introducing the water-processed high-K ZrO2 dielectric, the fully aqueous solution-grown In-B-O/ZrO2 TFTs exhibit excellent device performance, with a mobility of ~11 cm2/(V s), an on/off current of ~105, a subthreshold swing of 0.19 V/dec, a low operating voltage of 5 V and superior bias stress stability. Our research opens up new avenues for low-cost, large-area green oxide electronic devices with superior performance.

Study of Structural, Optical and Electrical Properties of MA(FA)SnICl2 Perovskite Thin Films Synthesized by One-Step Spin Coating

Study of Structural, Optical and Electrical Properties of MA(FA)SnICl2 Perovskite Thin Films Synthesized by One-Step Spin Coating

Effect of anti-solvent chlorobenzene on bottom micro-porous structure of perovskite light-absorbing layer

Anti-solvent technology plays an important role in one-step solution-processed spin-coating method for perovskite solar cells. In this article, we studied the effect of chlorobenzene as anti-solvent added at different time during one-step spin-coating for thin film of perovskite. We found that dropping chlorobenzene at different time would affect the amount of chlorobenzene entering the precursor solution, resulting in the growth of microporous structures in the perovskite layer. Early or late dropping of chlorobenzene produced a microporous structure layer. Although the top view of the perovskite layer was complete, a cross-sectional perspective shows the presence of micro-porous structures in the perovskite layer. When the chlorobenzene was dripped at 25 s, it was seen from the PL spectrum that the micro-porous structure at the bottom of the perovskite layer was less porous and the film quality was better. Moreover, the effect of dropping of chlorobenzene at different time on the characteristic size of the micro-porous structure at the bottom of the perovskite film was revealed by statistical analysis. A possible mechanism on the formation of the bottom micro-porous structure of perovskite film was proposed. Our work suggests the effect of one-step solution-processed spin-coating method for structure of perovskite layer by using chlorobenzene as an anti-solvent.

Characteristic of Methyl-Ammonium Lead Bromide Perovskites Solar Cells Fabricated By One-Step Spin Coating Process for the Application of Transparent Photovoltaics

Perovskite solar cells (PSCs) based on organic-inorganic halide have experienced an unprecedentedly rapid development when the first efficient perovskite-based solar device with solid-state structure was reported in 2009. Also, solution-processed organic-inorganic halide perovskites are currently established as the hottest area of interest in the world of photovoltaics, ensuring low manufacturing cost and relatively simple process and high conversion efficiencies. Methylammonium lead bromide (MAPbBr3) is one of the researched halide perovskite materials for transparent photovoltaics and high open circuit voltage (Voc) solar cells. Here, we have investigated MAPbBr3 absorber layer to increase the Voc and average visible transmittance. The MAPbBr3 perovskite films were fabricated by one-step spin coating process. The properties of MAPbBr3 perovskite films were found to be strongly influenced by the time to spray of anti-solvent solution (chlorobenzen). The result that the MAPbBr3 layer appropriately sprayed with chlorobenzen is beneficial to film quality and device efficiency because the nucleation of MAPbBr3 layer was affected by the anti-solvent engineering, which affected the film crystallite, density, and surface morphology. The MAPbBr3 layer by optimized 7~8 second (time to spray after spinning) showed the best efficiency of above 6.5 % with reproducibility. This research was also supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2019R1A2C4070248).

In Situ Grazing-Incidence Wide-Angle Scattering Reveals Mechanisms for Phase Distribution and Disorientation in 2D Halide Perovskite Films.

2D hybrid halide perovskites with the formula (A')2 (A)n -1 Pbn I3 n +1 have remarkable stability and promising efficiency in photovoltaic and optoelectronic devices, yet fundamental understanding of film formation, key to optimizing these devices, is lacking. Here, in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) is used to monitor film formation during spin-coating. This elucidates the general film formation mechanism of 2D halide perovskites during one-step spin-coating. There are three stages of film formation: sol-gel, oriented 3D, and 2D. Three precursor phases form during the sol-gel stage and transform to perovskite, first giving a highly oriented 3D-like phase at the air/liquid interface followed by subsequent nucleations forming slightly less oriented 2D perovskite. Furthermore, heating before crystallization leads to fewer nucleations and faster removal of the precursors, improving orientation. This outlines the primary causes of phase distribution and perpendicular orientation in 2D perovskite films and paves the way for rationally designed film fabrication techniques.

Enhanced performance of perovskite photodetectors fabricated by two-step spin coating approach

Metal halide perovskite films were prepared using two different deposition techniques, namely one-step spin coating (OSSC) and two-step spin coating (TSSC) and used as the active layer in perovskite photodetectors (PDs). Surface morphology studies revealed that perovskite thin films grown by OSSC exhibited large density of pin holes and non-uniform surface coverage. While, the film produced by TSSC shows full surface coverage with lesser pin holes. By comparing the device performance of the photodetectors based on OSSC and TSSC deposited films, we found that TSSC deposited film based PD demonstrated a significant enhancement in the performance (Responsivity of 1.05 A/W and detectivity of 1.27 × 1011 Jones @ −1 V) in comparison to the PD based on OSSC deposited films (Responsivity of 0.019 A/W and a detectivity of 1.77 × 109 Jones @ −1 V), which can be attributed to the higher absorbance, lesser trap density, narrower trap width, larger carrier mobility and lower leakage current, arising from better surface morphology and crystallinity of TSSC deposited films. Impedance analysis of PD prepared from TSSC film showed a relatively large charge recombination resistance and a long lifetime than PD fabricated from OSSC film, signifying less charge recombination events, which is in consistent with the high performance achieved with the TSSC film based PD.

One-step solution synthesis of white-light-emitting films via dimensionality control of the Cs–Cu–I system

Low-dimensional lead-free luminescent halides have emerged as highly promising phosphors for white-light emission. Recently, we reported a broadband blue-emitting copper(I) iodide-based material, Cs3Cu2I5, with a high photoluminescence quantum yield (PLQY) (∼90%) and a zero-dimensional nature, providing significant dimensionality for the photoactive site. However, this material is insufficient as a white-light emitter owing to the deficient yellow emission. In this paper, we report a novel yellow luminescent phosphor, CsCu2I3, with a 1D structure for the photoactive site. This material exhibits a broadband emission centered at ∼560 nm with a PLQY of ∼8%. We demonstrate a thin film with white-light emission that can be fabricated using one-step spin-coating of a mixed precursor solution of 1D CsCu2I3 (yellow) and 0D Cs3Cu2I5 (blue).

Properties of Perovskite Materials and Devices Fabricated Using the Solvent Engineered One-Step Spin Coating Method

Properties of Perovskite Materials and Devices Fabricated Using the Solvent Engineered One-Step Spin Coating Method

Growth of CH3NH3PbI3 Perovskite on Stainless Steel Substrate Layered by ZnO Nanoparticles Using One-Step Spin Coating Route

In this work, we report the preparation of CH3NH3PbI3 perovskite using one-step spin coating route for solar cell application. CH3NH3I• PbI2•DMF•DMSO complexes were coated on stainless steel as a subtrate layered by ZnO nanoparticles as an electron transport layer. To obtain samples with a special performance, we annealed the samples at a temperature of 100, 120, and 140°C for 10 minutes. The samples were then characterized by means of XRD, SEM/EDX, and Spectroscopic Ellipsometry. The analysis of XRD data presented that the CH3NH3PbI3 perovskites were successfully prepared and crystallized in tetragonal structure confirming from crystalline planes (110) and (220). Meanwhile, the particle size of the samples prepared at a temperature of 100, 120, and 140°C presented 42.96, 54.73, and 55.19 nm, respectively with coincide with the SEM images. The results indicated that the increase in temperature during synthesis influenced the particle growth. Furthermore, the characterization using Spectroscopic Ellipsometry exhibited that the CH3NH3PbI3 successfully layered on the substrate sizing nano metric scale that open high opportunity to be applied to solar cells with high performance.

Influence of coating steps of perovskite on low-temperature amorphous compact TiOx upon the morphology, crystallinity, and photovoltaic property correlation in planar perovskite solar cells

The fabrication of high-efficiency solution-processable perovskite solar cells has been achieved using mesostructured films and compact titanium dioxide (TiO2) layers in a process that involves high temperatures and cost. Here, we present an efficient approach for fabricating chemical-bath-deposited, low-temperature, and low-cost amorphous compact TiOx-based planar heterojunction perovskite solar cells by one-step and two-step coatings of the perovskite layer. We also investigate the effect of the number of perovskite coating steps on the compact TiOx layer. The grazing incidence wide-angle X-ray scattering technique is used to clarify the relationship between morphology, crystallinity, and photovoltaic properties of the resulting devices. Analysis of the films revealed that one-step spin-coating of perovskite exhibited an enhancement of film quality and crystallization that correlates to photovoltaic performance 1.5 times higher than that of a two-step-coated device. Our findings show that the resulting morphology, crystallinity, and device performances are strongly dependent on the number of coating steps of the perovskite thin layer on the compact TiOx layer. This result is useful knowledge for the low-cost production of planar perovskite solar cells.

Solution-Processed Ultrathin TiO2 Compact Layer Hybridized with Mesoporous TiO2 for High-Performance Perovskite Solar Cells.

The electron transport layer (ETL) is a key component of perovskite solar cells (PSCs) and must provide efficient electron extraction and collection while minimizing the charge recombination at interfaces in order to ensure high performance. Conventional bilayered TiO2 ETLs fabricated by depositing compact TiO2 (c-TiO2) and mesoporous TiO2 (mp-TiO2) in sequence exhibit resistive losses due to the contact resistance at the c-TiO2/mp-TiO2 interface and the series resistance arising from the intrinsically low conductivity of TiO2. Herein, to minimize such resistive losses, we developed a novel ETL consisting of an ultrathin c-TiO2 layer hybridized with mp-TiO2, which is fabricated by performing one-step spin-coating of a mp-TiO2 solution containing a small amount of titanium diisopropoxide bis(acetylacetonate) (TAA). By using electron microscopies and elemental mapping analysis, we establish that the optimal concentration of TAA produces an ultrathin blocking layer with a thickness of ∼3 nm and ensures that the mp-TiO2 layer has a suitable porosity for efficient perovskite infiltration. We compare PSCs based on mesoscopic ETLs with and without compact layers to determine the role of the hole-blocking layer in their performances. The hybrid ETLs exhibit enhanced electron extraction and reduced charge recombination, resulting in better photovoltaic performances and reduced hysteresis of PSCs compared to those with conventional bilayered ETLs.

Application of mixed-organic-cation for high performance hole-conductor-free perovskite solar cells

ABX3-type organic lead halide perovskites have gained increasing attention as light harvester for solar cells due to their high power conversion efficiency (PCE). Recently, it has become a trend to avoid the use of expensive hole-transport materials (HTMs) and precious metals, such as Au, to be competitive in future commercial development. In this study, we fabricated mixed-cation perovskite-based solar cells through one-step spin-coating using methylammonium (CH3NH3+) and formamidinium (HN=CHNH3+) cations to extend the optical absorption range into the red region and enhance the utilization of solar light. The synthesized hole-conductor-free cells with carbon electrode and mixed cations exhibited increased short-circuit current, outperforming the cells prepared with pure methylammonium, and PCE of 10.55%. This paper proposes an efficient approach for fabricating high-performance and low-cost perovskite solar cells.

High-Efficiency Solution-Processed Inorganic Metal Halide Perovskite Light-Emitting Diodes.

This paper reports highly bright and efficient CsPbBr3 perovskite light-emitting diodes (PeLEDs) fabricated by simple one-step spin-coating of uniform CsPbBr3 polycrystalline layers on a self-organized buffer hole injection layer and stoichiometry-controlled CsPbBr3 precursor solutions with an optimized concentration. The PeLEDs have maximum current efficiency of 5.39 cd A-1 and maximum luminance of 13752 cd m-2 . This paper also investigates the origin of current hysteresis, which can be ascribed to migration of Br- anions. Temperature dependence of the electroluminescence (EL) spectrum is measured and the origins of decreased spectrum area, spectral blue-shift, and linewidth broadening are analyzed systematically with the activation energies, and are related with Br- anion migration, thermal dissociation of excitons, thermal expansion, and electron-phonon interaction. This work provides simple ways to improve the efficiency and brightness of all-inorganic polycrystalline PeLEDs and improves understanding of temperature-dependent ion migration and EL properties in inorganic PeLEDs.

PB69 一括製膜による液晶性有機半導体/ポリマー積層構造の作製とトランジスタ評価(分子配向エレクトロニクス,ポスター発表,2015年日本液晶学会討論会)

PB69 一括製膜による液晶性有機半導体/ポリマー積層構造の作製とトランジスタ評価(分子配向エレクトロニクス,ポスター発表,2015年日本液晶学会討論会)

Controllable intermediates by molecular self-assembly for optimizing the fabrication of large-grain perovskite films via one-step spin-coating

Abstract In the past two years, the introduction of dimethylsulfoxide (DMSO) has recognized as an effective way to prepare high-quality pervoskite films. During the developed DMSO process, the formation of an intermediate phase has proven to uniform crystal growth rates between CH 3 NH 3 I (MAI) and PbI 2 in common solvents. In this work, controllable intermediates were obtained in dimethylformamide (DMF) by additional solvent of DMSO, which tend to be closely packed by means of intermolecular self-assembly. In addition, the bond strength and chemical composition of intermediate phase were investigated with FTIR and TGA. The use of different ratios of DMSO leads to four different complexes of MAI·PbI 2 ·DMF and MAI·PbI 2 ·(DMSO) y (y = 0.6, 1.5, 1.9), thus dramatically influencing the crystallization of perovskite films. Of these complexes, optimized MAI·PbI 2 ·(DMSO) 1.5 intermediate adduct enables highly dense perovskite thin films with large grain size and enhances efficient perovskite solar cells with high charge carrier lifetime.