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Fabrication of Two-Dimensional Crystalline Organic Films by Tilted Spin Coating for High-Performance Organic Field-Effect Transistors
摘要： We developed a facile method for fabricating large-area two-dimensional (2D) organic highly crystalline films and extended it to organic thin-film transistor arrays. Tilted spinning provided oriented flow at the three-phase contact line and 2D crystalline film that consisted of layer-by-layer stacked 2,7-diocty[1]benzothieno[3,2-b]benzothiophene (C8-BTBT) was obtained facilely for organic thin-film transistor (OTFT). The extracted field-effect mobility is 4.6 cm-2 V-1 s-1 but with non-ideal features. By applying this method to microdroplet arrays, oriented crystal was fabricated, and the channel region for OTFTs was covered by adjusting the spinning speed. By tuning the tilt angle (θ) of the revolving substrate, we fabricated high-performance OTFT arrays with average and maximum mobilities of 7.5 and 10.1 cm-2 V-1 s-1, respectively, that exhibited high reliability factors of over 90 % and were closed to ideal transistors. These results suggest that high-quality crystalline film can be obtained via a facile tilted spinning method.
关键词： oriented flow,reliability factor,tilted spin coating,two-dimensional,highly crystalline film
更新于2025-09-19 17:15:36
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Investigating the influence of the solution-processing method on the morphological properties of organic semiconductor films and their impact on OLED performance and lifetime
摘要： The morphological properties of organic semiconductor films deposited by blade coating and spin coating were investigated. The effect of these solution coating methods in fabricating the hole transport layer (HTL) and emissive layer (EML) of OLEDs was also examined. Transient photoluminescence measurements showed that blade-coated films have longer exciton lifetimes than spin-coated films, indicating that blade coating leads to films with less aggregated and more uniform morphologies. OLEDs with a blade-coated CBP:Ir(ppy)3 EML exhibited an external quantum efficiency (EQE) at 20 mA/cm2 of 8.6 % versus 6.4 % in case of device with the same structure but with a spin-coated EML. Additionally, the blade coated CBP:Ir(ppy)3-based device showed a decrease in electroluminescence emission peak by about 52% from its initial value after 20 min of electrical aging, whereas for the spin-coated device, the decrease was 74%. The higher efficiency and longer lifetime in the blade coated devices is likely a result of a more uniform or less aggregated film morphology. These findings demonstrate that blade coating is a promising solution-based fabrication technique to enable more efficient and longer-lived small molecule, solution-coated OLEDs and organic optoelectronic devices.
关键词： Blade coating,OLEDs,Lifetime,Organic semiconductors,Spin coating,Morphology
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Bifacial CdS/CdTe Solar Cell using Transparent Barium Copper Sulfide as a Hole Transport Layer
摘要： We report the properties of earth-abundant p-type transparent BaCu4S3 (BCS) thin films deposited by solution-based method. Our films of 100 nm thickness show transparency > 70% over the visible and near-infrared regions. We study the bifacial photovoltaic performance of CdTe solar cells using BCS as a hole transport layer. The BCS deposition etches the CdTe to leave a Te rich surface which can help to reduce the barrier height. Our best device, completed with ITO on the BCS, when illuminated from the glass side illumination (? = 12.3 %) shows improved performance relative to our standard Cu/Au back contact, with increased Voc and FF. For film side illumination, Jsc is low and (? reaches just 1%). Once optimized, this earth-abundant transparent BCS could serve as an effective, inexpensive, low-toxicity back contact layer for bifacial CdTe solar cell.
关键词： spin coating,bifacial,hole transport layer,CdTe
更新于2025-09-19 17:13:59
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Zirconia quantum dots for a nonvolatile resistive random access memory device
摘要： We propose a nonvolatile resistive random access memory device by employing nanodispersion of zirconia (ZrO2) quantum dots (QDs) for the formation of an active layer. The memory devices comprising a typical sandwich structure of Ag (top)/ZrO2 (active layer)/Ti (bottom) are fabricated using a facile spin-coating method. The optimized device exhibits a high resistance state/low resistance state resistance difference (about 10 Ω), a good cycle performance (the number of cycles larger than 100), and a relatively low conversion current (about 1 μA). Atomic force microscopy and scanning electron microscope are used to observe the surface morphology and stacking state of the ZrO2 active layer. Experimental results show that the ZrO2 active layer is stacked compactly and has a low roughness (Ra=4.49 nm) due to the uniform distribution of the ZrO2 QDs. The conductive mechanism of the Ag/ZrO2/Ti device is analyzed and studied, and the conductive filaments of Ag ions and oxygen vacancies are focused on to clarify the resistive switching memory behavior. This study offers a facile approach of memristors for future electronic applications.
关键词： Resistive switching,Spin coating,Memory device,Zirconia quantum dot
更新于2025-09-19 17:13:59
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Synthesis and characterization of inorganic K3Bi2I9 perovskite thin films for lead-free solution processed solar cells
摘要： Bismuth halide perovskites have been proposed as a non-toxic and chemically stable alternative to lead halide perovskites. Despite being highly stable, the devices based on bismuth perovskites have not been able to compete with the lead counterparts in terms of its ef?ciencies. The compounds that have been extensively studied i.e. Cs3Bi2I9 and MA3Bi2I9 form 0D (dimer) structures that possess wide indirect band gaps and poor charge transport properties which hinders the performance of devices based on these materials. Theoretical studies have revealed that replacing bigger A cation like Cs/MA by smaller cation like potassium (K) could favor the formation of layered 2D structures rather than 0D structure. We have synthesized inorganic K3Bi2I9 perovskite thin ?lms by facile one-step spin coating method and investigated its structural, optical and morphological properties. The fabricated ?lms showed strong absorption in UV and visible region of solar spectrum and possess optical band gap (cid:1)2 eV. On comparison with the Cs analogue, it is observed that reduction in the cation size (Cs to K) hardly changes the band gap of K3Bi2I9 ?lms which implies that the band gap of A3Bi2I9 perovskite is insensitive to A-site variation. Films deposited on preheated substrates showed comparatively good coverage without voids on the ?lm surface. Our preliminary studies on this material showed that the ?lms deposited by one-step solution method favored 0D structure rather than the expected 2D layered structure.
关键词： Thin ?lms,K3Bi2I9 perovskite,XRD,Spin coating,XPS
更新于2025-09-19 17:13:59
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Sequential deposition method of TiO <sub/>2</sub> /CH <sub/>3</sub> NH <sub/>3</sub> PbI <sub/>3</sub> films for solar cell application
摘要： Seeking to study innovative solar cell compositions with the goal to reach the highest energy efficiency level attainable, the aim of this study was to develop a route to obtain a solar cell composed by hybrid perovskite (CH3NH3PbI3) using a sequential deposition method through the techniques of spin-coating and immersion. Initially, the deposition of PbI2 thin film of was performed on a FTO/glass substrate coated with TiO2, which was subsequently converted into perovskite crystals through spin coating using a CH3NH3I solution. The influence of the PbI2 layer thickness on the formation of CH3NH3PbI3 crystals was evaluated. The hydrophilic characteristic of TiO2 affects the distribution of the crystals nucleation sites, since PbI2 possesses a non-polar liquid characteristic. The characterization of the perovskite thin films showed that thickness affects directly the bandgap and the surface morphology, revealing the presence of dendritic structures and acicular crystals. Both growth and coverage increased for thinner layers of PbI2. It was also possible to observe an increased uniformity in the film for smaller PbI2 layers.
关键词： solar cell,immersion,sequential deposition,TiO2,spin-coating,perovskite,CH3NH3PbI3
更新于2025-09-16 10:30:52
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The humidity-insensitive fabrication of efficient CsPbI <sub/>3</sub> solar cells in ambient air
摘要： Recently, CsPbI3 perovskite solar cells (PSCs) have shown a breakthrough in photovoltaic performance due to their constantly improving power conversion efficiencies (PCEs) because of their admirable photoelectric properties and enhanced thermal stability. However, most fabrication processes take place inside a nitrogen glove box because CsPbI3 is notoriously sensitive to moisture. These tedious and rigorous operational conditions restrict CsPbI3 PSCs' commercialization. In our research, in order to solve the awkward situation of fabricating CsPbI3 PSCs without ambient moisture, we successfully developed an easy, one-step anti-solvent hot substrate (Anti-hot) spin-coating method to fabricate CsPbI3 film. Pre-heating the substrate could change the saturated vapor pressure of the mixed solvents and accelerate the precursor concentrations up to the supersaturation limit. Meanwhile, the anti-solvent method could induce heterogeneous nucleation. As a result, we could efficaciously control nucleation generation and grain growth under ambient moisture conditions and resist erosion and damage by molecular water. Finally, uniform and compact CsPbI3 film could be achieved and the corresponding PSCs reached up to 15.91% in a high humidity environment (RH, ≥50%). We hope that our exploration can provide a synthetic approach for producing high-quality CsPbI3 film for PSCs under ambient conditions.
关键词： anti-solvent hot substrate spin-coating,CsPbI3,perovskite solar cells,humidity-insensitive,ambient air
更新于2025-09-16 10:30:52
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Synthesis and physical properties of low cost, non toxic, earth abundant p-type CuInS2 thin film as absorber layer for photovoltaic application
摘要： Copper Indium disulfide (CIS) thin films were synthesized by chemical solution deposition method on glass substrates. Low processing temperatures of 420 oC under nitrogen annealing is key feature of this study.CIS thin films on glass were prepared by dissolving copper (II) chloride, Indium (III) chloride and Thiourea in 2-methoxy ethanol. Surface structures and morphology of the synthesized CIS thin films studied by grazing incidence X-ray diffraction and atomic force microscopy, respectively, revealed a phase pure growth and smooth morphology with average crystallite sizes of the order of 2.97 nm. Hall Effect study demonstrates that synthesized CIS thin film is p-type with holes as majority charge carriers. Temperature dependence of optical band gap was studied in the wavelength range of 200-1400 nm and was found to decrease with increasing temperature. Detailed results on synthesis and physical properties will be presented.
关键词： Copper Indium disulfide,Optical properties,Photovoltaic,Spin coating
更新于2025-09-16 10:30:52
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Ultraviolet photodetectors based on doped ZnO films
摘要： In this paper, we report the realization of ultraviolet (UV) photodetector based on doped ZnO films. The ZnO p-n junction was fabricated on indium tin oxide (ITO) coated glass, which consists of n-type and p-type layers based on Ga-doped (2 at.%) and N-doped (20 at.%) ZnO films, respectively. The current-voltage (IV) characteristics, photosensitivity, photoresponsitivity, and photocurrent gain were derived to determine the performance of the device. At 5 V reverse bias, the ZnO-based UV photodetector exhibits photosensitivity of 10.9, photoresponsivity of 2.1 × 10-2 AW-1, and photoconductive gain of 7.2 × 10-2.
关键词： ultraviolet photodetectors,sol-gel spin coating,p-n junction,doped ZnO films
更新于2025-09-12 10:27:22
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Transforming polymorphs of Co-doped TiO2 nanoparticles: an efficient photo-electrode for dye-sensitized solar cells
摘要： Simple sol–gel assisted spin coating technique was used to prepare cobalt-doped TiO2 films for the application of dye-sensitized solar cells (DSSC). TiO2 photo-electrodes with few Co concentrations (0, 0.025, 0.05, 0.075 and 0.1 M) were prepared on conducting glass substrates. The morphology, structure and composition of the Co:TiO2 films were observed using SEM, XRD and EDAX analysis. The average crystallite size of Co:TiO2 nanoparticles obtained from diffractograms are in the range of 3–12 nm. The transformation of polymorphs from anatase to rutile and vice versa for the increasing concentrations of Co in TiO2 films is observed. The values of optical bandgap energy for Co-doped films are observed to be higher than the pure TiO2 film and the highest is for the dopant level of 0.025 M. Doping of 0.1 M Co in TiO2 enhances the power conversion efficiency of DSSC by 65% compared to pure TiO2 film, demonstrating the influence of Co doping on the functioning of DSSC.
关键词： TiO2,Co-doped TiO2,Sol–gel,DSSC,Spin coating technique
更新于2025-09-12 10:27:22