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1.
A highly efficient planar heterojunction OSC based on zinc phthalocyanine (ZnPc)/fullerene (C60) by controlling the orientation of the ZnPc by using copper iodide (CuI) as the interfacial layer is reported. The proportion of face-on ZnPc molecules was increased significantly on the CuI layer compared to the layer without the CuI layer, which was analyzed with wide-angle X-ray scattering (WAXS) and optical absorption. The power conversion efficiency (PCE) of the orientation controlled planar heterojunction OSC was remarkably enhanced to 3.2 ± 0.1% compared with 1.2 ± 0.1% of the conventional OSCs without the control of the molecular orientation. By inserting the 3-nm-thick CuI layer, JSC, VOC and FF have increased from 4.6 ± 0.2 to 8.9 ± 0.2 mA cm?2, from 0.48 ± 0.01 to 0.59 ± 0.02 V, and from 0.56 ± 0.01 to 0.61 ± 0.02, respectively. VOC enhancement is discussed with the result of the ultraviolet photoemission spectra (UPS) measurements.  相似文献   

2.
《Current Applied Physics》2015,15(9):1010-1014
A polycrystalline MgZnO/ZnO bi-layer was deposited by using a RF co-magnetron sputtering method and the MgZnO/ZnO bi-layer TFTs were fabricated on the thermally oxidized silicon substrate. The performances with varying the thickness of ZnO layer were investigated. In this result, the MgZnO/ZnO bi-layer TFTs which the content of Mg is about 2.5 at % have shown the enhancement characteristics of high mobility (6.77–7.56 cm2 V−1 s−1) and low sub-threshold swing (0.57–0.69 V decade−1) compare of the ZnO single layer TFT (μFE = 5.38 cm2 V−1 s−1; S.S. = 0.86 V decade−1). Moreover, in the results of the positive bias stress, the ΔVon shift (4.8 V) of MgZnO/ZnO bi-layer is the 2 V lower than ZnO single layer TFT (ΔVon = 6.1 V). It reveals that the stability of the MgZnO/ZnO bi-layer TFT enhanced compared to that of the ZnO single layer TFT.  相似文献   

3.
In this study, P3HT:PCBM organic photovoltaic (OPV) devices, with or without ZnO nanoparticles buffer layer between the photoactive layer (P3HT:PCBM) and the cathode (Al top electrode), were fabricated. The devices were annealed at 145 °C either before or after depositing the top electrode. The objective of this study was to investigate the effects of the ZnO buffer layer and pre-/post-fabrication annealing on the general performance of these devices. The short-circuit current density (JSC), open-circuit voltage (VOC) and the external quantum efficiency (EQE) of the OPV devices were improved by the insertion of the ZnO layer and post-fabrication annealing. The post-fabrication annealed devices, with or without the ZnO layer, exhibited higher values of JSC, VOC and EQE than those of similar devices annealed before depositing the Al metal. This can be attributed to, among other things, improved charge transport across the interface between the photoactive layer and the Al top electrode as a result of post-annealing induced modification of the interface morphology.  相似文献   

4.
We demonstrated the effect of ZnO (different wt%)-coated LiMnPO4-based cathode materials for electrochemical lithium ion batteries. ZnO-coated LiMnPO4 cathode materials were prepared by the sol-gel method. X-ray diffraction (XRD) analysis indicates that there is no change in structure caused by ZnO coating, and field emission scanning electron microscopy (FESEM) images depict the closely packed particles. Galvanostatic charge-discharge tests show the ZnO-coated LiMnPO4 sample has an enhanced electrochemical performance as compared to pristine LiMnPO4. The 2 wt% of ZnO-based LiMnPO4 exhibited maximum discharge capacity of 102.2 mAh g?1 than pristine LiMnPO4 (86.2 mAh g?1) and 1 wt% of ZnO-based LiMnPO4 (96.3 mAh g?1). The maximum cyclic stability of 96.3 % was observed in 2 wt% of ZnO-based LiMnPO4 up to 100 cycles. This work exhibited a promising way to develop a surface-modified LiMnPO4 using ZnO for enhanced electrochemical performance in device application.  相似文献   

5.
《Current Applied Physics》2015,15(5):654-661
Three kinds of donor–acceptor (D–A) type photovoltaic polymers were synthesized based on 2,7-carbazole and thieno[3,4-c]pyrrole-4,6-dione (TPD). The conjugation of weakly electron (e)-donating 2,7-carbazole and strongly e-accepting TPD moieties yielded a deep highest occupied molecular orbital (HOMO) and its energy level was fine-controlled to be −5.72, −5.67 and −5.57 eV through the incorporation of thiophene (T), thieno[3,2-b]thiophene (TT) and bithiophene (BT) as a π-bridge. Polymer:[6,6]-phenyl-C71 butyric acid methyl ester (PC71BM) based bulk heterojunction solar cells exhibited a high open-circuit voltage (VOC) in the range, 0.86–0.94 V, suggesting good agreement with the measured HOMO levels. Despite the high VOC, the thiophene (or thienothiophene)-containing PCTTPD (or PCTTTPD) showed poor power conversion efficiency (PCE, 1.14 and 1.25%) because of the very low short-circuit current density (JSC). The voltage-dependent photocurrent and photoluminescence quenching measurements suggested that hole transfer from PC71BM to polymer depends strongly on the HOMO level of the polymer. The PCTTPD and PCTTTPD devices suffered from electron–hole recombination at the polymer/PC71BM interfaces because of the insufficient energy offset between the HOMOs of the polymer and PC71BM. The PCBTTPD:PC71BM device showed the best PCE of 3.42% with a VOC and JSC of 0.86 V and 7.79 mA cm−2, respectively. These results show that photovoltaic polymers should be designed carefully to have a deep HOMO level for a high VOC and sufficient energy offset for ensuring efficient hole transfer from PC71BM to the polymer.  相似文献   

6.
We have fabricated optically active ZnO inverse opals by infiltrating polystyrene (PS) opal templates using an electrodeposition process. Compared with bare ZnO films also prepared by electrodeposition, the three-dimensional (3D) ordered ZnO structure exhibits markedly enhanced photoluminescence. The effect of photonic band gap on PL spectra is also clearly observed from the ZnO inverse opal structure.  相似文献   

7.
《Current Applied Physics》2010,10(4):990-996
This study examined the effects of Ga content in the CIGS absorber layer on the properties of the corresponding thin films and solar cells fabricated using a co-evaporation technique. The grain size of CIGS films decreased with increasing Ga content presumably because Ga diffusion during the 2nd stage of the co-evaporation process is more difficult than In diffusion. The main XRD peaks showed a noticeable shift to higher diffraction angles with increasing Ga content, which was attributed to Ga atoms substituting for In atoms in the chalcopyrite structure. Band gap energy and the net carrier concentration of CIGS films increased with Ga/(In + Ga) ratios. Regarding the solar cell parameters, the short circuit current density (JSC) decreased linearly with Ga/(In + Ga) ratios due to the lack of absorption in the long-wavelength portion of the spectrum, while the open circuit voltage (VOC) increase with those. However, VOC values at high Ga/(In + Ga) regions (>0.35) was far below than those extrapolated from the low Ga contents regions, finally resulting in an optimum Ga/(In + Ga) ratio of 0.28 where the solar cell showed the highest efficiency of 15.56% with VOC, JSC and FF of 0.625 V, 35.03 mA cm−2 and 0.71, respectively.  相似文献   

8.
ZnO-coated LiMn2O4 cathode materials were prepared by a combustion method using glucose as fuel. The phase structures, size of particles, morphology, and electrochemical performance of pristine and ZnO-coated LiMn2O4 powders are studied in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge test, and X-ray photoelectron spectroscopy (XPS). XRD patterns indicated that surface-modified ZnO have no obvious effect on the bulk structure of the LiMn2O4. TEM and XPS proved ZnO formation on the surface of the LiMn2O4 particles. Galvanostatic charge/discharge test and rate performance showed that the ZnO coating could improve the capacity and cycling performance of LiMn2O4. The 2 wt% ZnO-coated LiMn2O4 sample exhibited an initial discharge capacity of 112.8 mAh g?1 with a capacity retention of 84.1 % after 500 cycles at 0.5 C. Besides, a good rate capability at different current densities from 0.5 to 5.0 C can be acquired. CV and EIS measurements showed that the ZnO coating effectively reduced the impacts of polarization and charge transfer resistance upon cycling.  相似文献   

9.
Zn0.98−xCuxV0.02O (x=0, 0.01, 0.02 and 0.03) samples were synthesized by the sol–gel technology to dope up to 3% Cu in ZnO. Investigations of structural, optical and magnetic properties of the samples have been done. The results of X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) indicated that the V and Cu ions were incorporated into the crystal lattices of ZnO. With Cu doping concentration increasing up to 2 at%, the XRD results showed that all diffraction peaks corresponded to the wurtzite structure of ZnO. Photoluminescence (PL) measurements showed that Zn0.98−xCuxV0.02O powders exhibited that the position of the ultraviolet (UV) emission peak of the samples showed an obvious red-shift and the green emission peak enhanced significantly with Cu doping in ZnVO nanoparticle. Magnetic measurements indicated that room temperature ferromagnetism (RTFM) of Zn0.98−xCuxV0.02O was an intrinsic property when Cu concentration was less than 3 at%. The saturation magnetization (Ms) of Zn0.98−xCuxV0.02O (x=0, 0.01 and 0.02) increased with the increase of the Cu concentration.  相似文献   

10.
In this research work, SCAPS-1D (Solar Cell Capacitance Simulator in one Dimension) is used to simulate the CZTSSe (Cu2ZnSn(S,Se)4) solar cell with Al/ZnO:Al/ZnO(i)/CdS/CZTSSe/Mo structure. The simulation results have been compared and validated with real experimental results. After that, an effective receipt is proposed with the aim of improving the efficiency of the CZTSSe solar cell, in which a BSF layer is inserted using various materials (SnS, CZTSSe and CZTSe). The obtained results show that the efficiencies of CZTSSe solar cells are increased from 12.3% to 15.7%, 15.3% and 15% by the insertion of SnS, CZTSSe and CZTSe materials as BSF layers, respectively. This enhancement corresponds with a BSF layer thickness of 30 nm and doping concentration of 1E18 cm−3. Next, an optimization of BSF layers thickness has been conducted. The optimum value of thickness is considered at 40 nm with an enhancement ratio in efficiency of 36.70%, 26.21% and 21.53% for SnS, CZTSSe and CZTSe, respectively. Better performances have been noted for SnS material. The optimized CZTSSe solar cell with SnS as a BSF layer achieves an efficiency of 16.95% with JSC = 36.34 mA/cm2, VOC = 0.69 V, and FF = 67% under Standard Test Conditions (AM1.5 G and cell temperature of 25 °C).  相似文献   

11.
《Current Applied Physics》2010,10(6):1452-1455
In this study, we report the fabrication of ZnO metal-semiconductor-metal UV photodetector (MSM UV PD) by deposition ZnO thin film on poly propylene carbonate (PPC) plastic substrate using direct current (DC) sputtering technique, and Nickel (Ni) contact as electrodes. The structural, optical and electrical properties of the ZnO thin film were investigated by using atomic force microscopy (AFM), X-Ray diffraction (XRD) measurement, and photoluminescence (PL). The electrical characteristics of the detector were investigated using the current–voltage (IV) measurements, the dark- and photo-currents were found to be 1.04 and 93.80 μA, respectively. Using forward dark conditions at 5 volt; the barrier height ΦB was calculated to be 0.675 eV. Under incident wavelength of 385 nm, it was found that the maximum responsivity (R) of the Ni/ZnO/Ni MSM PD was found to be 1.59 A/W.  相似文献   

12.
In this paper, a numerical simulation on the open-circuit voltage (VOC) of the P-GaSb window/P-Ga0.8In0.2As0.18Sb0.82 emitter/N-Ga0.8In0.2As0.18Sb0.82 base/N-GaSb structure thermophotovoltaic (TPV) cell is performed and an analysis of the effects of device parameters on VOC is presented. The simulations are carried out with the fixed spectral control filter and for the radiator temperature of Trad = 950 °C, cell temperature of Tdio = 27 °C, the radiation photons are injected from the front P-region. The thick P-Ga0.8In0.2As0.18Sb0.82 emitter with the longer minority carrier diffusion length is the main optical absorption region. The simulated results are compared with the available experimental data, and a good agreement is obtained. The effects of the layer thickness, carrier concentration, injection level and main recombination mechanisms (e.g. the radiative, Auger, bulk Shockley–Read–Hall (SRH) and surface recombination) of the P-Ga0.8In0.2As0.18Sb0.82 emitter and N-Ga0.8In0.2As0.18Sb0.82 base on VOC are analyzed. It indicates that the parameters of the emitter region have stronger effect than that of the base region on VOC. Dependence of VOC on the material parameters of P-GaSb window layer is also analyzed, both the carrier concentration and thickness of P-GaSb window layer have effect on VOC. Moreover, adding a back surface reflector (BSR) to the TPV cell can increase VOC.  相似文献   

13.
Fe-doped ZnO porous microspheres composed of nanosheets were prepared by a simple hydrothermal method combined with post-annealing, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller N2 adsorption–desorption measurements and photoluminescence (PL) spectra. In this paper we report Fe doping induced modifications in the structural, photoluminescence and gas sensing behavior of ZnO porous microspheres. Our results show that the crystallite size decreases and specific surface area increases with the increase of Fe doping concentration. The PL spectra indicate that the 4 mol% Fe-doped ZnO has higher ratio of donor (VO and Zni) to acceptor (VZn) than undoped ZnO. The 4 mol% Fe-doped ZnO sample shows the highest response value to ppb-level n-butanol at 300 °C, and the detected limit of n-butanol is below 10 ppb. In addition, the 4 mol% Fe -doped ZnO sample exhibits good selectivity to n-butanol. The superior sensing properties of the Fe-doped porous ZnO microspheres are contributed to higher donor defects contents combined with larger specific surface area.  相似文献   

14.
《Current Applied Physics》2014,14(1):127-131
We have incorporated silicon nanoparticles (Si-nps) into organic–inorganic hybrid solar cells in place of the chalcogenide nanocrystals that are commonly employed in such devices. Poly(3,4-ethylenedioxy-thiophene):poly(styrene sulfonate) (PEDOT:PSS) and phenyl-C61-butyric acid methyl ester (PCBM) were employed as hole and electron transport layers, respectively. We used transmission electron microscopy, Raman spectroscopy, and ultraviolet–visible spectroscopy to fully characterize the Si-nps and relate their characteristics to the performance of the hybrid solar cells. We show that the open circuit voltage (VOC) was largely dependent on the size and amorphous volume fraction of Si-nps. Our findings imply that the amorphous phase and small size of Si-nps produce band gap widening that increases the VOC when coupled with PCBM as acceptor. The maximum VOC was up to 0.634 V in a hybrid device with 5.7 nm Si-nps.  相似文献   

15.
Alternating donor-acceptor type copolymers, poly[{5,11-di(9′-heptadecanyl)indolo[3,2-b]carbazole}-alt-{2,5-di(thiophen-2-yl)thiazolo[5,4-d]thiazole-5,5′-diyl}] (PIC-TZ) and poly[{6,6′,12,12′-tetraoctylindeno[1,2-b]fluorene}-alt-{2,5-di(thiophen-2-yl)thiazolo[5,4-d]thiazole-5,5′-diyl}] (PIF-TZ), were synthesized and examined for applications in polymeric photovoltaic cells. The polymers have a fused coplanar main backbone with good planarity for intermolecular packing and high charge mobility. The indolocarbazole and indenofluorene units contain two or four binding sites for alkyl substituents that have pronounced solution processiblity compared to the carbazole and fluorene moieties. The number-average molecular weights (Mn) of the synthesized polymers were determined to be 11,000 g/mol (PDI = 2.27) for PIC-TZ, and 17,000 g/mol (PDI = 1.77) for PIF-TZ. The optical band gap of PIC-TZ and PIF-TZ in film was determined to be 2.14 eV and 2.21 eV, respectively, and an electrochemical study confirmed the desirable HOMO/LUMO levels of the copolymers, which enabled efficient electron transfer and a high open circuit voltage (VOC) when blending them with fullerene derivatives. The space charge limited current mobility measurements showed a hole mobility of 10−3 cm2 V−1 s−1 for the copolymers. When the polymers were blended with [6,6]phenyl-C61-butyric acid methyl ester (PCBM), PIC-TZ showed the best performance with VOC, short-circuit current and power conversion efficiency of 0.86 V, 4.16 mA/cm2 and 1.64%, respectively, under AM 1.5G illumination conditions (100 mW cm−2).  相似文献   

16.
Polyaniline nanowires (PANI NWs) were deposited onto fluorine-doped tin oxide (FTO) glass substrate using the cyclic voltammetric method with aniline monomer precursor in HCl aqueous solution. The secondary oxidation peak plays an important role in polymerization of aniline monomer and the optimization of catalytic activity of PANI-based counter electrodes was achieved by controlling the number of cycles. The photovoltaic performance of the dye-sensitized solar cells (DSSCs) with PANI NWs counter electrodes (CEs) was optimized at 4th cycles, and then following parameters were obtained: Jsc = 17.2 mA cm−2, Voc = 0.71 V, FF = 59.3%, and efficiency (η) = 7.24%. While, Jsc = 14.7 mA cm−2, Voc = 0.77 V, FF = 70.6%, and efficiency (η) = 7.98% in cells with Pt CEs. The PANI NWs were attractive as an alternative CEs for the low-cost DSSCs instead of Pt.  相似文献   

17.
In this work a new method has been employed to synthesize nanocrystalline ZnO powder under hydrothermal conditions at 80 °C using aqueous Zn(NO3)2·6H2O solution and diethylamine (DEA) as the starting materials. The ZnO powder prepared by this novel method was characterized by XRD, energy dispersive X-ray spectroscopy (EDX), FTIR and UV–vis techniques. Calculation based on XRD data revealed ZnO particles to be of nanometer size (∼33 nm). The ZnO powder was subsequently used to make its thin film which exhibited flower like morphology when examined by SEM. Thin ZnO films were sensitized with N719 dye, (Bu4N)2[Ru(dcbpyH)2(NCS)2], and used as photo-anode to construct sandwich type dye-sensitized solar cell (DSSC). With such cells, VOC = 0.680 V, JSC = 0.61 mA cm−2, fill factor = 0.43 and overall conversion efficiency η = 0.23% were achieved on illumination with visible light (80 mW cm−2).  相似文献   

18.
Copper zinc tin sulfide solar cells were fabricated by using spray pyrolysis from a window layer to an absorber layer. ZnS and In2S3 buffer layers were deposited on the TiO2 layer, and the photovoltaic characteristics were investigated. The ZnS buffer demonstrated a poor photovoltaic performance because of its poor surface coverage and micro-cracks at fluorine-doped tin oxide/TiO2 layers. The In2S3 buffer layer sprayed at low temperature (<360 °C) showed a large difference between photo and dark currents beyond the open-circuit voltage (VOC). When the spraying temperature exceeded 390 °C, the devices showed high dark leakage currents at reverse biases because of the high conductivity of the buffer layer, resulting in decreased VOC and short-circuit current density (JSC). The optimum temperature for spraying In2S3 is 360 °C, and the best performing device showed 410 mV, 30.4 mA/cm2, 35.3%, and 4.4% of VOC, JSC, fill factor, and efficiency, respectively.  相似文献   

19.
The fabrication of the 2D periodic structures in ZnO thin films by magnetron sputtering on the opal matrices was developed. The microstructures were characterized by AFM and SEM. The spontaneous and stimulated emissions of the ZnO layers on opal were studied at N2 laser excitation (λ = 337 nm). The stimulated emission near 397 nm was observed at room temperature from ZnO–opal structure. The threshold of the electron–hole plasma recombination laser process was 300 kW/cm2 for this structure. This threshold is two orders of magnitude smaller of that one for the flat ZnO–SiO2 films owing to DFB resonator effect in 2D structure.  相似文献   

20.
Transparent and efficient poly-ZnO ultraviolet Schottky diodes grown at different temperatures with indium-tin-oxide (ITO) as the metallic contact layer were fabricated with hydrogen peroxide (H2O2) applied as a surface treatment at 70 °C for 20 min. Analysis via field-emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) demonstrated that the ZnO films underwent gradual oxidation and that H2O2 treatment resulted in an interfacial ZnO2 layer that covered the ZnO surface. IV measurements indicated that the ideality factor and the Schottky barrier height improved with increasing shunt resistance, and the trade-off between film quality and the degree of oxidation revealed that films grown at 400 °C exhibited the best diode characteristics.  相似文献   

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