Control of Optical and Electrical Properties of ZnO Films for Photovoltaic Applications

ABSTRACTZnO films were grown by radical-source molecular beam epitaxy (RS-MBE) on sapphire and glass substrates, and they were characterized in terms of Hall mobility and optical transmission. Undoped ZnO films exhibit a low intrinsic defect density and optical properties close to bulk ZnO. By Ga doping, a resistance ρ as low as 2×10−4 Ωcm could be achieved. Balancing high conductivity and low transmission losses due to free carrier absorption in the infrared, the optimum was obtained for ρ=3.4×10−4Ωcm, electron mobility μe=37 cm2/Vs and an average transmission T of 96% in the wavelength range 400-1100 nm. Polycrystalline growth on glass yields slightly reduced but still good film quality (μe=30 cm2/Vs, T=90%). By the incorporation of Mg, conducting Mg0.3Zn0.7O films with an increased band gap up to ∼ 4eV were realized.

Download Full-text

Textured Zinc Oxide by Expanding Thermal Plasma CVD: the Effect of Aluminum Doping

MRS Proceedings ◽

10.1557/proc-730-v3.9 ◽

2002 ◽

Vol 730 ◽

Cited By ~ 1

Author(s):

R. Groenen ◽

E.R. Kieft ◽

J.L. Linden ◽

M.C.M. van de Sanden

Keyword(s):

Surface Texture ◽

Thermal Plasma ◽

Band Gap Energy ◽

Zno Films ◽

Free Carrier Absorption ◽

Plasma Cvd ◽

Reflection And Transmission ◽

Glass Substrates ◽

Direct Measurements ◽

Carrier Absorption

AbstractAluminum doped ZnO films are deposited on glass substrates at a temperature of 200°C by expanding thermal plasma CVD. Surface texture, morphology and crystal structure have been studied by AFM, SEM and XRD. A rough surface texture, which is essential for application as front electrode in thin film solar cells, is obtained during deposition. The addition of aluminum as a dopant results in distinct differences in film morphology, a transition from large, rounded crystallites to a more pyramid-like structure is observed. The structure of films is hexagonal with a preferred crystal orientation in the faces (002) and (004), indicating that films are oriented with their c-axes perpendicular to the substrate plane. In addition, spectroscopic ellipsometry is used to evaluate optical and electronic film properties. The presence of aluminum donors in doped films is confirmed by a shift in the ZnO band gap energy from 3.32 to 3.65 eV. In combination with reflection and transmission measurements in the visible and NIR ranges, film resistivities have been obtained from the free-carrier absorption. These results are consistent with direct measurements. Resistivities as low as 6.0 10-4 Ωcm have been obtained.

Download Full-text

Electrical and Photoelectrical Properties of Nanostructured ZnO Thin Films for Photovoltaic Applications

MRS Proceedings ◽

10.1557/proc-1013-z04-09 ◽

2007 ◽

Vol 1013 ◽

Author(s):

Stefan Antohe ◽

Cezar Tazlaoanu ◽

Gabriel Socol ◽

Larisa Magherusan ◽

Ionut Enculescu ◽

...

Keyword(s):

Thin Films ◽

Optical Glass ◽

Visible Region ◽

Solar Spectrum ◽

Growth Direction ◽

Zno Thin Films ◽

Zno Films ◽

Glass Substrates ◽

Photoelectrical Properties ◽

Photovoltaic Applications

AbstractStructural, electrical and optical characterizations of nanostructured ZnO thin films used as photosensitized electrodes in photovoltaic cells applications are reported. Nanostructured ZnO thin films were deposited on optical glass substrates by pulsed-laser deposition (PLD), their structure and morphology being optimized for photovoltaic applications. Structural analysis of the samples by X-ray diffraction revealed that the films consist of a hexagonal-close-packed wurtzite type phase ZnO, (001) preferentially oriented in the growth direction. The ZnO films are highly transparent in visible region of solar spectrum, and exhibit electrical resistivities in the range 10-4 - 10-2Ω.m

Download Full-text

Engineering of TiO2 or ZnO—Graphene Oxide Nanoheterojunctions for Hybrid Solar Cells Devices

Photonics ◽

10.3390/photonics8030075 ◽

2021 ◽

Vol 8 (3) ◽

pp. 75

Author(s):

Duarte Carreira ◽

Paulo A. Ribeiro ◽

Maria Raposo ◽

Susana Sério

Keyword(s):

Graphene Oxide ◽

Solar Cells ◽

Fossil Fuels ◽

Electrical Characterization ◽

Modern Society ◽

Clean Energy ◽

Zno Films ◽

Layer By Layer ◽

Glass Substrates ◽

Rc Circuit

It is currently of huge importance to find alternatives to fossil fuels to produce clean energy and to ensure the energy demands of modern society. In the present work, two types of hybrid solar cell devices were developed and characterized. The photoactive layers of the hybrid heterojunctions comprise poly (allylamine chloride) (PAH) and graphene oxide (GO) and TiO2 or ZnO films, which were deposited using the layer-by-layer technique and DC-reactive magnetron sputtering, respectively, onto fluorine-doped tin oxide (FTO)-coated glass substrates. Scanning electron microscopy evidenced a homogeneous inorganic layer, the surface morphology of which was dependent on the number of organic bilayers. The electrical characterization pointed out that FTO/(PAH/GO)50/TiO2/Al, FTO/(PAH/GO)30/ZnO/Al, and FTO/(PAH/GO)50/ZnO/Al architectures were the only ones to exhibit a diode behavior, and the last one experienced a decrease in current in a low-humidity environment. The (PAH/GO)20 impedance spectroscopy study further revealed the typical impedance of a parallel RC circuit for a dry environment, whereas in a humid environment, it approached the impedance of a series of three parallel RC circuits, indicating that water and oxygen contribute to other conduction processes. Finally, the achieved devices should be encapsulated to work successfully as solar cells.

Download Full-text

4-QAM OFDM Data Switching via Free Carrier Absorption in Si-Rich SiC Waveguide

IEEE Journal of Selected Topics in Quantum Electronics ◽

10.1109/jstqe.2020.3033282 ◽

2021 ◽

Vol 27 (3) ◽

pp. 1-11

Author(s):

Yen-Wei Hsueh ◽

Chih-Hsien Cheng ◽

Cai-Syuan Fu ◽

Huai-Yung Wang ◽

Bo-Ji Huang ◽

...

Keyword(s):

Free Carrier ◽

Free Carrier Absorption ◽

Carrier Absorption ◽

Data Switching

Download Full-text

Microscopic FCA System for Depth-Resolved Carrier Lifetime Measurement in SiC

Materials Science Forum ◽

10.4028/www.scientific.net/msf.924.269 ◽

2018 ◽

Vol 924 ◽

pp. 269-272 ◽

Cited By ~ 2

Author(s):

Shinichi Mae ◽

Takeshi Tawara ◽

Hidekazu Tsuchida ◽

Masashi Kato

Keyword(s):

Carrier Lifetime ◽

Laser Light ◽

Probe Laser ◽

Free Carrier Absorption ◽

Cross Sectional ◽

Lifetime Measurements ◽

Control Distribution ◽

System A ◽

Excitation Laser ◽

Carrier Absorption

For high voltage SiC bipolar devices, carrier lifetime is an important parameter, and for optimization of device performance, we need to control distribution of the carrier lifetime in a wafer. So far, there have been limited systems for depth-resolved carrier lifetime measurements without cross sectional cut. In this study, we adopted a free carrier absorption technique and made local overlapping of the probe laser light with excitation laser light to develop depth-resolved carrier lifetime measurements. We named the developed system a microscopic FCA system and demonstrated measurement results for samples with and without intentional carrier lifetime distribution.

Download Full-text

A study of vibrations of boron and phosphorus in silicon by infra-red absorption

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1965.0169 ◽

1965 ◽

Vol 287 (1408) ◽

pp. 64-88 ◽

Cited By ~ 67

Keyword(s):

Second Harmonic ◽

Force Constants ◽

Published Data ◽

Free Carrier Absorption ◽

Local Modes ◽

Pure Silicon ◽

Infra Red ◽

Carrier Absorption ◽

Experimental Problem ◽

Silicon Doped

The infra-red absorption spectrum of silicon doped with high densities of boron and phosphorus has been measured from 1 to 60 μm and at temperatures between 5 and 290 °K in order to observe the local and band mode vibrational absorption activated by these impurities. The major experimental problem, that of achieving a high degree of electrical compensation to eliminate free carrier absorption, was solved by using fast electron bombardment to introduce a controllable number of trapping centres. A series of experiments was conducted to eliminate the effects of these centres from the spectrum of the chemical impurities. The characteristic spectra of the substitutional boron and phosphorus have been analysed in detail in terms of the theory of Dawber & Elliott. For local modes activated by boron isotopes close agreement with theory has been found in number of lines, strength and frequency. From the latter it is estimated that the local force constants are weakened by less than 10 % on substituting boron for silicon in the lattice. Second harmonic lines are observed at a frequency 0.25 % less than twice that of the fundamentals. The band modes exhibit a striking in-band resonance at 0.0546 eV which was not theoretically predicted. This is attributed to phosphorus and analysis shows that the theory can give such a resonance but not with parameters associated with substitutional phosphorus and unchanged force constants. Most of the remaining features in the band modes can be interpreted satisfactorily in terms of substitutional boron but this requires some modification to published data on the density of states for pure silicon. Critical points for TO( L ), TO( X ) and LA( L ) phonons are clearly identified in the spectra.

Download Full-text