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1.
Sensors (Basel) ; 20(1)2020 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-31948055

RESUMO

Numerous studies have addressed the use of perovskite materials for fabricating a wide range of optoelectronic devices. This study employs the deposition of an electron transport layer of C60 and an Ag electrode on CH3NH3PbBr3 perovskite crystals to complete a photodetector structure, which exhibits a metal-semiconductor-metal (MSM) type structure. First, CH3NH3PbBr3 perovskite crystals were grown by inverse temperature crystallization (ITC) in a pre-heated circulator oven. This oven was able to supply uniform heat for facilitating the growth of high-quality and large-area crystals. Second, the different growth temperatures for CH3NH3PbBr3 perovskite crystals were investigated. The electrical, optical, and morphological characteristics of the perovskite crystals were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible spectroscopy, and photoluminescence (PL). Finally, the CH3NH3PbBr3 perovskite crystals were observed to form a contact with the Ag/C60 as the photodetector, which revealed a responsivity of 24.5 A/W.

2.
Nanoscale Res Lett ; 14(1): 236, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-31309306

RESUMO

This paper proposes a new encapsulation structure for aluminum nitride-based deep UV light-emitting diodes (DUV-LEDs) and eutectic flip chips containing polydimethylsiloxane (PDMS) fluid doped with SiO2 nanoparticles (NPs) with a UV-transparent quartz hemispherical glass cover. Experimental results reveal that the proposed encapsulation structure has considerably higher light output power than the traditional one. The light extraction efficiency was increased by 66.49% when the forward current of the DUV-LED was 200 mA. Doping the PDMS fluid with SiO2 NPs resulted in higher light output power than that of undoped fluid. The maximum efficiency was achieved at a doping concentration of 0.2 wt%. The optical output power at 200 mA forward current of the encapsulation structure with NP doping of the fluid was 15% higher than that without NP doping. The optical output power of the proposed encapsulation structure was 81.49% higher than that of the traditional encapsulation structure. The enhanced light output power was due to light scattering caused by the SiO2 NPs and the increased average refractive index. The encapsulation temperature can be reduced by 4 °C at a driving current of 200 mA by using the proposed encapsulation structure.

3.
Nanoscale Res Lett ; 14(1): 182, 2019 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-31144059

RESUMO

This study proposes a novel direct-lit mini-chip-scale packaged light-emitting diode (mini-CSPLED) backlight unit (BLU) that used quantum dot (QD) film, diffusion plate, and two prism films to improve brightness uniformity. Three different luminous intensity units, 120° mini-CSPLED, 150° mini-CSPLED, and 180° mini-CSPLED with different emission angle structures were fabricated using a CSP process. In terms of component characteristics, although the 180° mini-CSPLED light output power is about loss 4% (at 10 mA) compared with 150° mini-CSPLED, it has a large emission angle that forms a planar light source that contributes to improving the BLU brightness uniformity and reduced quantity of LEDs at the same area. In terms of BLU analysis, the blue mini-CSPLEDs with different emission angles excite the different QD film thicknesses; the chromaticity coordinates conversion to the white light region. The BLU brightness increases as the QD film thickness increases from 60, 90, and 150 µm. This result can achieve a brightness uniformity of 86% in a 180° mini-CSPLED BLU + 150-µm-thick QD films as compared to the 120° mini-CSPLED BLU and 150° mini-CSPLED BLU.

4.
Disabil Rehabil ; : 1-6, 2019 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-30939070

RESUMO

PURPOSE: To develop a tablet-based participation measure and to evaluate its reliability and acceptability to an older Chinese population in rehabilitation settings. METHOD: A multidimensional, self-reported participation measure, the Participation Measure-3 Domains, 4 Dimensions (PM-3D4D), was programed into mobile application software and presented on tablet computers. To explore the reliability of the tablet-based PM-3D4D, 80 adults in rehabilitation outpatient settings aged ≥65 years completed the tablet and the paper versions of the measure at baseline and at 1-week follow-up. Intraclass correlation coefficients were calculated for concordance and test-retest reliability. Participants' acceptability toward the two versions of the measure was described. RESULTS: The tablet-based PM-3D4D showed good to excellent test-retest reliability (Intraclass correlation coefficients = 0.79 ∼ 0.96) and high concordance with the paper-form (Intraclass correlation coefficients = 0.74-1.00). Approximately, 44% participants reported preference for the tablet-based measure, and 20% reported preference for the paper-form measure. Many participants found the tablet-based measure user-friendly, convenient, and environmentally-friendly. CONCLUSIONS: Findings of this study provide supportive evidence for administering the tablet-based PM-3D4D to an older Chinese population in rehabilitation settings and suggest a promising measurement methodology for future clinical practice. Implications for rehabilitation The developed tablet-based participation measure, the Participation Measure-3 Domains, 4 Dimensions (PM-3D4D), fills a critical void for an efficient and reliable rehabilitation outcome measure tailored to the needs of older adults in rehabilitation settings. The tablet-based PM-3D4D is a reliable outcome measure. Most of the older adults in rehabilitation settings preferred to use the tablet-based participation measure than the paper-form measure; and very few of them reported difficulty with using the tablet-version measure. A high concordance was found between data collected by the tablet version PM-3D4D and data collected by the paper version PM-3D4D.

5.
Materials (Basel) ; 12(6)2019 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-30934571

RESUMO

The poor stability of CsPbX3 quantum dots (QDs-CsPbX3) under wet conditions is still considered to be a key issue. In order to overcome this problem, this study presents a high molecular weight polymer matrix (polymethylmethacrylate, PMMA) incorporated into the QDs-CsPbBr3 to improve its stability and maintain its excellent optical properties. In this study, the Cs2CO3, PbO, Tetrabutylammonium Bromide (TOAB) powder, oleic acid, and toluene solvent were uniformly mixed and purified to prepare high-quality QDs powders. Then, hexane was used as a dispersing agent for the QD powder to complete the perovskite QDs-CsPbBr3 solution. Finally, a solution with different proportions of quantum dots CsPbBr3 and PMMA was prepared and discussed. In the preparation of thin films, firstly, a thin film with the structure of glass/QD-CsPbBr3/PMMA was fabricated in a glove box using a well-developed QDs-CsPbBr3 solution by changing the ratio of CsPbBr3:PMMA. The material analysis of QDs-CsPbBr3 thin films was performed with photoluminescence (PL), transmittance, absorbance, and transmission electron microscopy (TEM). The structures and morphologies were further examined to study the effect of doped PMMA on perovskite QDs-CsPbBr3.

6.
Nanomaterials (Basel) ; 9(1)2019 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-30669436

RESUMO

We describe a method to enhance power conversion efficiency (PCE) of MAPbI3 perovskite solar cell by inserting a FAPbX3 perovskite quantum dots (QD-FAPbX3) layer. The MAPbI3 and QD-FAPbX3 layers were prepared using a simple, rapid spin-coating method in a nitrogen-filled glove box. The solar cell structure consists of ITO/PEDOT:PSS/MAPbI3/QD-FAPbX3/C60/Ag, where PEDOT:PSS, MAPbI3, QD-FAPbX3, and C60 were used as the hole transport layer, light-absorbing layer, absorption enhance layer, and electron transport layer, respectively. The MAPbI3/QD-FAPbX3 solar cells exhibit a PCE of 7.59%, an open circuit voltage (Voc) of 0.9 V, a short-circuit current density (Jsc) of 17.4 mA/cm², and a fill factor (FF) of 48.6%, respectively.

7.
Micromachines (Basel) ; 9(5)2018 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-30424138

RESUMO

In this work, a MAPbBr3 quantum dot (QD-MAPbBr3) layer was prepared by a simple and rapid method. Octylammonium bromide (OABr) gives the MAPbBr3 better exciton binding energy, good surface morphology, and stability. To form a nanocrystalline thin film on indium tin oxide (ITO) glass, the QD-MAPbBr3 film was coated by a spin-coating method in a nitrogen-filled glove box and the NiOx film was used as an adhesive layer and hole transport layer. The highest transmittance of MAPbBr3 on NiOx/ITO glass was around 75% at 700 nm. This study also reported a high transparent and perovskite bulk-free ITO/NiOx/QD-MAPbBr3/C60/Ag solar cell where the NiOx, QD-MAPbBr3, and C60 were used as a hole transport layer, active layer, and electron transport layer, respectively.

8.
Nanomaterials (Basel) ; 8(7)2018 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-29941783

RESUMO

In this study, we demonstrate an easy and reliable solution-processed technique using an extra adductive in the perovskite precursor solution. Using this method, a dense and uniform morphology with full surface coverage and highly fluorescent films with nanoscale crystal grains can be obtained. The high exciton binding energy in the resulting films employing octylammonium bromide (OAB) adductives proved that high fluorescence originated from the quantum confinement effect. The corresponding perovskite light-emitting diodes (PeLEDs) that were based on this technique also exhibited excellent device performance.

9.
Nanoscale Res Lett ; 13(1): 140, 2018 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-29740717

RESUMO

In this study, the perovskite layers were prepared by two-step wet process with different CH3NH3I (MAI) concentrations. The cell structure was glass/FTO/TiO2-mesoporous/CH3NH3PbI3 (MAPbI3)/spiro-OMeTAD/Ag. The MAPbI3 perovskite films were prepared using high and low MAI concentrations in a two-step process. The perovskite films were optimized at different spin coating speed and different annealing temperatures to enhance the power conversion efficiency (PCE) of perovskite solar cells. The PCE of the resulting device based on the different perovskite morphologies was discussed. The PCE of the best cell was up to 17.42%, open circuit voltage of 0.97 V, short current density of 24.06 mA/cm2, and fill factor of 0.747.

10.
Nanoscale ; 9(45): 17802-17806, 2017 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-29115332

RESUMO

Comprehensive studies were carried out to understand the origin of the current hysteresis effects in highly efficient C60-CH3NH3PbI3(MAPbI3) heterojunction solar cells, using atomic-force microscopy, transmittance spectra, photoluminescence spectra, X-ray diffraction patterns and a femtosecond time-resolved pump-probe technique. The power conversion efficiency (PCE) of C60-MAPbI3 solar cells can be increased to 18.23% by eliminating the point (lattice) defects in the MAPbI3 thin film which is fabricated by using the one-step spin-coating method with toluene washing treatment. The experimental results show that the point defects and surface defects of the MAPbI3 thin films can be minimized by varying the dropping time of the washing solvent. The point defects (surface defects) can be reduced with an (a) increase (decrease) in the dropping time, resulting in an optimized dropping time for obtaining the defect-minimized MAPbI3 thin film deposited on top of the C60 thin film. Consequently, the formation of the defect-minimized MAPbI3 thin film allows for high-efficiency MAPbI3 solar cells.

11.
Nanoscale Res Lett ; 12(1): 556, 2017 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-28975569

RESUMO

This investigation reports on the characteristics of MAPbI3 perovskite films on obliquely sputtered ITO/glass substrates that are fabricated with various sputtering times and sputtering angles. The grain size of a MAPbI3 perovskite film increases with the oblique sputtering angle of ITO thin films from 0° to 80°, indicating that the surface properties of the ITO affect the wettability of the PEDOT:PSS thin film and thereby dominates the number of perovskite nucleation sites. The optimal power conversion efficiency (Eff) is achieved 11.3% in a cell with an oblique ITO layer that was prepared using a sputtering angle of 30° for a sputtering time of 15 min.

12.
Nanomaterials (Basel) ; 7(7)2017 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-28671613

RESUMO

Dimethylformamide/dimethyl sulfoxide solvent mixtures were used as the CH3NH3PbI3 (MAPbI3) precursor solvent in a one-step spin coating method to fabricate smooth and hydrophilic crystalline MAPbI3 thin films on top of hydrophobic carbon-60 (C60) thin film for highly efficient photovoltaics. The structural, optical, and excitonic characteristics of the resultant MAPbI3 thin films were analyzed using X-ray diffraction (XRD), atomic-force microscopy, absorbance spectroscopy, photoluminescence (PL) spectrometry, and nanosecond time-resolved PL. There was a trade-off between the crystallinity and surface roughness of the MAPbI3 thin films, which strongly influenced the device performance of MAPbI3-based photovoltaics. The high power conversion efficiency (PCE) of 17.55% was achieved by improving the wettability of MAPbI3 precursor solutions on top of the C60 thin films. In addition, it was predicted that the fill factor and PCE could be further improved by increasing the crystallinity of the MAPbI3 thin film while keeping it smooth.

13.
Nanoscale Res Lett ; 12(1): 35, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28091950

RESUMO

This study investigates the optoelectronic characteristics of gallium nitride (GaN)-based thin-film light-emitting diodes (TF-LEDs) that are formed by a two-step transfer process that involves wet etching and post-annealing. In the two-step transfer process, GaN LEDs were stripped from sapphire substrates by the laser lift-off (LLO) method using a KrF laser and then transferred onto ceramic substrates. Ga-K nanorods were formed on the surface of the GaN-based TF-LEDs following photo-assisted chemical etching and photo-enhanced post-annealing at 100 °C for 1 min. As a result, the light output power of GaN-based TF-LEDs with wet etching and post-annealing was over 72% more than that of LEDs that did not undergo these treatments.

14.
Materials (Basel) ; 9(9)2016 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-28773874

RESUMO

This study determines the effects of annealing treatment on the structure and the optical and electronic behaviors of the mixed (FAPbI3)1-x(MAPbBr3)x perovskite system. The experimental results reveal that (FAPbI3)1-x(MAPbBr3)x (x ~ 0.2) is an effective light-absorbing material for use in inverted planar perovskite solar cells owing to its large absorbance and tunable band gap. Therefore, good band-matching between the (FAPbI3)1-x(MAPbBr3)x and C60 in photovoltaic devices can be controlled by annealing at various temperatures. Accordingly, an inverted mixed perovskite solar cell with a record efficiency of 12.0% under AM1.5G irradiation is realized.

15.
Nanomaterials (Basel) ; 6(10)2016 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-28335311

RESUMO

This work presents mixed (FAPbI3)1-x(MAPbBr3)x perovskite films with various composition ratios, x (x = 0-1), which are formed using the spin coating method. The structural, optical, and electronic behaviors of the mixed (FAPbI3)1-x(MAPbBr3)x perovskite films are discussed. A device with structure glass/indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/mixed perovskite/C60/BCP/Ag was fabricated. The mixed perovskite film was an active light-harvesting layer. PEDOT: PSS was a hole transporting layer between the ITO and perovskite. Both C60 and bathocuproine (BCP) were electron transporting layers. MAPbBr3 was added to FAPbI3 with a composition ratio of x = 0.2, stabilizing the perovskite phase, which exhibited a uniform and dense morphology. The optimal device exhibited band matching with C60, resulting in a low series resistance (Rsh) and a high fill factor (FF). Therefore, the device with composition (FAPbI3)1-x(MAPbBr3)x and x = 0.2 exhibited outstanding performance.

16.
Nanoscale Res Lett ; 10(1): 404, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26474885

RESUMO

This work elucidates the optoelectronic properties of graphene/methylammonium lead iodide (MAPbI3)/titanium dioxide (TiO2)/porous Si heterostructure diodes. The porous silicon substrates can accommodate more MAPbI3/TiO2 than the polished silicon substrate such that the MAPbI3/TiO2/porous Si substrate heterostructures have better optoelectronic properties. Photocurrents from 300 to 900 nm were measured. The photocurrent is high in two ranges of wavelength, which are 300-460 nm and 520-800 nm. The photocurrent plateau covers all visible light (360 to 780 nm) except for cyan between 460 and 520 nm. Therefore, the graphene/MAPbI3/TiO2/porous Si heterostructure can be utilized as cyan sensors.

17.
Nanoscale Res Lett ; 10(1): 1020, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26243152

RESUMO

UNLABELLED: This work presents a CH3NH3PbI3/PCBM organic solar cell. Organic PCBM film and CH3NH3PbI3 perovskite film are deposited on the PEDOT: PSS/ITO glass substrate by the spin coating method. The performance of the organic solar cells was observed by changing the thickness of CH3NH3PbI3 perovskite. The thickness of a perovskite film can affect the carrier diffusion length in a device that strongly absorbs light in the red spectral region. The short-circuit current density and the power conversion efficiency were 21.9 mA/cm(2) and 11.99 %, respectively, for the sample with 210-nm-thick CH3NH3PbI3 perovskite active layer.

18.
Nanoscale Res Lett ; 9(1): 380, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25136284

RESUMO

This study investigates the extent to which the TiO2/graphene/TiO2 sandwich structure improves the performance of dye-sensitized solar cells (DSSCs) over that of DSSCs with the traditional structure. Studies have demonstrated that the TiO2/graphene/TiO2 sandwich structure effectively enhances the open circuit voltage (V oc), short-circuit current density (J sc), and photoelectrical conversion efficiency (η) of DSSCs. The enhanced performance of DSSCs with the sandwich structure can be attributed to an increase in electron transport efficiency and in the absorption of light in the visible range. The DSSC with the sandwich structure in this study exhibited a V oc of 0.6 V, a high J sc of 11.22 mA cm(-2), a fill factor (FF) of 0.58, and a calculated η of 3.93%, which is 60% higher than that of a DSSC with the traditional structure.

19.
Materials (Basel) ; 7(11): 7304-7313, 2014 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-28788247

RESUMO

CuZnO (CZO) films have attracted increasing amounts of attention due to their promising potential applications in semiconductor devices. ZnO shows n-type conductivity, and attempts have been made to dope several elements in ZnO to improve the electrical properties. This study investigated the electrical property transitions of CZO films and determined the copper concentration at which the conductivity of CZO films will change from n-type to p-type. In this study, CZO films were fabricated by ultrasonic spray pyrolysis with copper acetate, zinc acetate, and ammonium acetate precursor solution. The concentrations of Cu ions in the CZO films were controlled by the concentration ratios of copper acetate to zinc acetate in the precursor solutions. In addition, these samples were analyzed by Hall effect measurements, X-ray diffraction, transmittance measurements, and photoluminescence measurements. The results show that the conductivity of the CZO film changes from n-type to p-type when the copper ion concentration in the film is 5%.

20.
Materials (Basel) ; 7(2): 1261-1270, 2014 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-28788513

RESUMO

CuZnO (CZO) films have received considerable attention, owing to their potential applications in semiconductor devices, including gas sensors or solar cells. However, exactly how these films affect the properties of CZO films by using different Cu sources has seldom been investigated. This study demonstrates the feasibility of preparing CZO films by using different Cu sources via a simple ultrasonic spray method, in which copper nitrate and copper acetate were used as copper sources. Optical properties of CZO films prepared by copper nitrate and copper acetate were also investigated, based on transmittance and photoluminescence measurements. Additionally, the composition and the morphology of the films were investigated using the X-ray diffraction analysis and field emission scanning electron microscopy. The results of this study demonstrate that the CZO films prepared by using copper acetate exhibit better optical properties.

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