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Opt Lett ; 44(19): 4865-4868, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31568462


To unlock the full potential of the perovskite solar cell (PSC) photocurrent density and power conversion efficiency, the topic of optical management and design optimization is of absolute importance. Here, we propose a gradient-index optical design of the PSC based on a Gaussian-type front-side glass structure. Numerical simulations clarify a broadband light-harvesting response of the new design, showing that a maximal photocurrent density of 23.35 mA/cm2 may be expected, which is an increase by 1.21 mA/cm2 compared with that of the traditional flat-glass counterpart (22.14 mA/cm2). Comprehensive analysis of the electric field distributions elucidates the light-trapping mechanism. Furthermore, PSCs having the Gaussian index profile display superior optical properties and performance compared to those of the uniform index counterpart under varying conditions of perovskite layer thicknesses and incident angles. The simulation results in this study provide an effective design scheme to promote optical absorption in PSCs.

ACS Appl Mater Interfaces ; 11(40): 36727-36734, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31525907


Tin oxide (SnO2) is widely used in perovskite solar cells (PSCs) as an electron transport layer (ETL) material. However, its high surface trap density has already become a strong factor limiting PSC development. In this work, phosphoric acid is adopted to eliminate the SnO2 surface dangling bonds to increase electron collection efficiency. The phosphorus mainly exists at the boundaries in the form of chained phosphate groups, bonding with which more than 47.9% of Sn dangling bonds are eliminated. The reduction of surface trap states depresses the electron transport barriers, thus the electron mobility increases about 3 times when the concentration of phosphoric acid is optimized with 7.4 atom % in the SnO2 precursor. Furthermore, the stability of the perovskite layer deposited on the phosphate-passivated SnO2 (P-SnO2) ETL is gradually improved with an increase of the concentration. Due to the higher electron collection efficiency, the P-SnO2 ETLs can dramatically promote the power conversion efficiency (PCE) of the PSCs. As a result, the champion PSC has a PCE of 21.02%. Therefore, it has been proved that this simple method is efficient to improve the quality of ETL for high-performance PSCs.

Opt Express ; 27(11): 16195-16205, 2019 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-31163803


The optical properties of hexagonal GaN microdisk arrays grown on sapphire substrates by selective area growth (SAG) technique were investigated both experimentally and theoretically. Whispering-gallery-mode (WGM) lasing is observed from various directions of the GaN pyramids collected at room temperature, with the dominant lasing mode being Transverse-Electric (TE) polarized. A relaxation of compressive strain in the lateral overgrown region of the GaN microdisk is illustrated by photoluminescence (PL) mapping and Raman spectroscopy. A strong correlation between the crystalline quality and lasing behavior of the GaN microdisks was also demonstrated.

Nanotechnology ; 29(45): 45LT01, 2018 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-30160239


Enhanced photoluminescence and improved internal quantum efficiency were demonstrated for ultraviolet light emitting diodes (UV-LEDs) with Al nanohole arrays deposited on the top surface. The effects of the thickness and periodicity of the plasmonic structures on the optical properties of UV-LEDs were studied, and an optimized nanohole array parameter was illustrated. Classical electrodynamic simulations showed that the radiated power is mostly concentrated along the edge of the Al nanohole arrays. Even though no obvious dip was observed in the transmission spectra associated with localized surface plasmon resonance, significant improvements in radiatiative recombination and light extraction efficiency were demonstrated, indicating the influence of Al nanohole arrays on the light emission control of UV-LEDs. It is anticipated that the enhanced luminescence can be obtained for various emitting wavelengths by directly adjusting the periodicity and morphology of the Al nanohole arrays and this new technology can alleviate crystal quality requirements of III-nitride thin films in the development of high efficiency UV optoelectronic devices.

Medicine (Baltimore) ; 97(29): e11502, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30024532


BACKGROUND AND OBJECTIVE: The aim of this study was to compare the outcomes of transanal hemorrhoidal dearterialization (THD) and stapled hemorrhoidectomy (SH) in the treatment of hemorrhoids by a meta-analysis. METHODS: Randomized control trials (RCTs) comparing SH with THD were searched for in databases, including MEDLINE, PubMed, Web of science, Embase, and the Cochrane Library database. Data were independently extracted from each study, and a meta-analysis was performed using RevMan5.2 software. RESULTS: Eight RCTs, including 977 patients, were included in this meta-analysis. No statistically significant differences were noted between THD and SH in terms of total complications (OR, 0.93; 95% CI, 0.69, 1.25), but a significant differences were noted in terms of bleeding (OR, 1.85; 95% CI, 1.10, 3.10). The total recurrence rate was higher in THD than in SH on short-term follow-up; however, the recurrence rate was equal in both the THD and SH groups on long-term follow-up. The present study showed that no significant difference between SH and THD in terms of postoperative pain (OR, 0.43; 95% CI, -0.43, 1.29), operative time (OR, -3.12; 95% CI, -7.01, 0.77), hospital time (OR, -0.00; 95% CI, -0.21, 0.20), time before returning to work (OR,-0.50; 95%CI, -4.42,3.43), and reoperation rate (OR, 1.81; 95% CI, 0.93, 3.54). CONCLUSION: Our meta-analysis indicated that THD and SH are equally effective techniques for the treatment of hemorrhoids. However, future studies addressing cost-effectiveness, satisfaction rate, and recurrence rate over a long follow-up period are needed to validate these results.

Canal Anal/cirurgia , Hemorroidectomia/métodos , Hemorroidas/cirurgia , Grampeamento Cirúrgico/métodos , Hemorroidectomia/efeitos adversos , Humanos , Tempo de Internação/estatística & dados numéricos , Ligadura/métodos , Duração da Cirurgia , Satisfação do Paciente/estatística & dados numéricos , Complicações Pós-Operatórias/epidemiologia , Complicações Pós-Operatórias/etiologia , Ensaios Clínicos Controlados Aleatórios como Assunto , Recidiva , Reoperação/estatística & dados numéricos , Retorno ao Trabalho/estatística & dados numéricos , Grampeamento Cirúrgico/efeitos adversos , Resultado do Tratamento
Sci Rep ; 7(1): 14575, 2017 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-29109447


Recently, silicon single nanowire solar cells (SNSCs) serving as the sustainable self-power sources have been integrated into optoelectronic nanodevices under the driver of technology and economy. However, conventional SNSC cannot provide the minimum energy consumption for the operation of nanodevices due to its low power conversion efficiency (PCE). Here, we propose an innovative approach to combine the n-type silicon nanowires (SiNWs) with p-type poly(3,4-ethylthiophene):poly(styrenesulfonate) (PEDOT:PSS) to form the p + n heterojunction, which shows superior opto-electric performances. Besides, PEDOT:PSS also acts as a natural anti-reflection coating (ARC) with an excellent light-trapping capability, especially in the short-wavelength range. Importantly, the photovoltaic performances of Si/PEDOT:PSS SNSC can be well maintained even in large surface recombination velocity, due to the efficient field-effect passivation of PEDOT:PSS. The minority carrier concentration at outer surface of shallow p + n heterojunction is greatly reduced by the electric field, drastically suppressing the surface recombination compared to the conventional p-i-n homojunction SNSC. Furthermore, larger junction area of p + n heterojunction facilitates the separation of photo-generated charge carriers. These results demonstrate that the Si/PEDOT:PSS SNSC is a promising alternative for micro power application.