High Photovoltages in Cadmium Sulfide Films

Brandhorst, Henry W.; Acampora, F. L.; Potter, A. E.

doi:10.1063/1.1656118

Cited by 20 publications

(8 citation statements)

References 19 publications

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“…It is a straight line which shows log͑V och ͒ increases linearly with 1000/ T and implies that V och increases exponentially with 1000/ T. Such a behavior of V och with temperature was observed by Brandhorst and Potter 13 in Si and SiC films above room temperature ͑T Ͼ 333 K͒. In some Si films 13 they observed that V och increased more slowly with 1000/ T as the temperature was lowered below T Ͻ 333 K. However, in CdS films 10 and in one silicon film, 13 they found that V och increased with 1000/ T for a decrease of temperature and showed a peak at ϳ250 K and then decreased rapidly with 1000/ T for T Ͻ 250 K. In Cd 3 As 2 films, Zdanowicz et al 22 had also observed a small peak of height 35 V in the V och vs 1000/ T curve at ϳ240 K followed by a dip at 230 K and then a regular increase of V och with 1000/ T for 230 K Ͼ T Ͼ 90 K. However, after storing the film for 2 days they observed a big peak of height 140 V at ϳ200 K that was followed by a sharp decrease with 1000/ T such that V och was reduced to zero at 143 K and changed polarity for T Ͻ 143 K. After storage of 3 months, films showed a still higher peak of 200 V corresponding to T = 220 K which was followed by a sharp decrease with 1000/ T such that V och again became zero at 1000/ T =9 ͑i.e., for T = 110 K͒ and changed its polarity for T Ͻ 110 K. These Cd 3 As 2 films had been given a SiO x coating on the film surface. We have plotted curve 2 for the 400 K Ͼ T Ͼ 80 K temperature range in Fig.…”

Section: Intensity Dependence Of V Ochmentioning

confidence: 87%

“…The spectral response of photovoltage was of an inverted-V shape with a peak at ϳ500 nm wavelength. 10 Photovoltage varied linearly with intensity up to 50 mW/ cm 2 but increased at a smaller rate between 50 and 150 mW/ cm 2 intensity. 10 In CdS films 10 and also in a Si film, 13 the photovoltage increased with the decrease in temperature from 330 to ϳ230 K and then decreased with further lowering of the temperature.…”

Section: Introductionmentioning

confidence: 99%

“…10 Photovoltage varied linearly with intensity up to 50 mW/ cm 2 but increased at a smaller rate between 50 and 150 mW/ cm 2 intensity. 10 In CdS films 10 and also in a Si film, 13 the photovoltage increased with the decrease in temperature from 330 to ϳ230 K and then decreased with further lowering of the temperature. 13 They tried to attribute the occurrence of large photovoltages to the existence of multiple trapping levels.…”

Section: Introductionmentioning

confidence: 99%

“…A systematic study of the dependence of APV on the wavelength and intensity of incident light and the temperature was made by Brandhorst et al 10,13 in thin films of CdS, Si, and SiC. The CdS films were deposited on a quartz substrate at an angle of 45°from the normal.…”

Section: Introductionmentioning

confidence: 99%

“…Photovoltages, much larger than the band-gap energy ͑E g ͒ of the semiconductor, have been observed in obliquely deposited thin films of a large number of semiconductors [1][2][3][4][5][6][7][8][9][10][11][12][13][14] on transparent substrates under normal illumination. This effect is commonly known as the anomalous photovoltaic effect ͑APV͒.…”

Section: Introductionmentioning

confidence: 99%

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Phenomenological model of anomalously high photovoltages generated in obliquely deposited semiconductor films

Singh

Kumar

2008

Journal of Applied Physics

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Photovoltage in obliquely deposited films of semiconductors is found to be much higher in magnitude than the corresponding band gap of the semiconductor. Also, the magnitude of the photovoltage depends on the angle of deposition, the separation between the electrodes, the wavelength of the incident light, the intensity of the illumination and temperature, but this behavior is not understood well. In this work a phenomenological model of the generation of photovoltage along the horizontal plane of the obliquely deposited films on transparent substrates is presented for the first time. The model is based on the presence of obliquely grown grains separated by parallel grain boundaries and the existence of grain boundary potential barriers across the grain boundaries. In the case of semiconductor films with a high absorption coefficient for short wavelengths in the visible range, there occurs a relatively large photogeneration of carriers on the front side of the grain boundaries rather than on the back side, and this gives rise to a net photocurrent and a photovoltage across each grain boundary. The horizontal components of this photovoltage get added up due to a large number of grain boundaries lying between the electrodes on the front surface and produce a large photovoltage due to the series combination. An expression has been derived based on this model which shows that for low intensities of illumination the horizontal component V och of the photovoltage increases linearly with electrode separation, resistivity of the film, and the incident light intensity. It depends on the angle of deposition and under certain conditions it is expected to be maximum when the angle of deposition is 45°. The analysis can be applied to study the effect of increase in intensity or decrease in temperature on V och . It also shows that the photovoltage across the thickness of the obliquely deposited film V ocv is minimum for normal deposition and increases with the increase in the angle of oblique deposition.

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Section: Intensity Dependence Of V Ochmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phenomenological model of anomalously high photovoltages generated in obliquely deposited semiconductor films

Singh

Kumar

2008

Journal of Applied Physics

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Photovoltaic effect in polycrystalline ZnTe films

Patel

1985

Cryst. Res. Technol.

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Anoinaloris but, wcak photovoltaic cffect hits bceri observed in the case of thin polyerystalline %nTc films obliquely deposited on glass substrate. Photovoltagc o f t h e order of a fcw hiuidred millivolt per centimeter have been observed a t the ambient temperature. Optimized conditions for growing films to obtain maximum photovoltage havc been found. In order to explain the observed photovoltaic effect, a model comprising of a long chain of a,ligned microcells in the form of p-p+ homojunctions has been proposed. The implications are discussed. IiitroductioiiThe anomalous photovoltaic effect observed in thin films has aroused great in1,erest. Extensive studies of a range of materials have revealed beyond doubt that it is absolutely necessary to grow the filnis by oblique deposition in order t o produce the anomalous photovoltaic effect. It is reported in literature that the photovoltaic effect appears to be due to the photoresponse of p-n niicrojunctions (PENSAK, GOLDSTEIN; ADIROVICH et al. ; BRANDHORST et al.) or Dember effect (SCHWABE; PANKOVE) or grain boundaries (HUSTON; MXRZ; NOVIK;EL-SHAZLY et al.). In all the cases it is presumed that a large number of active crystallites arrange themselves in series, which produce the photovoltage.IGNATY UK, N O V~K have reported high photovoltage in epitaxially grown ZnTe films on ionic crystals. However from the point of view of the applications of the photovoltaic effect, it is necessary to grow the filiiis on a good inert substrate rather than ionic crystals. It appears that so far no reports have been published on photovoltaic effect in polycrystalline ZnTe filnis grown on glass substrates. The present paper describes weak anomalous photovoltaic effect observed in the case of ZnTe film grown on glass substrate. The optimized growth conditions in order to get niaxiniuni photovoltaic effect have been investigated and a possible niodel for i t is suggested and discussed. Experiiiierital procedureZnTc films were prepared by thermal evaporation from pure (99.998%) ZnTe powder on ultrasonically cleaned glass substrates in a vacuum of the order of Pa. The glass substrates in a vacuum of tJhe order of l'a. The glass substrates were held inclined to the diroction of the incident b m m of the vapour. The rate of evaporation was 5-6 r i m sec-1 arid was maintained constant for all depositions. The average thickness of the wedge films grown was about 100 nm and was kept the same for all sets of observations. The substrate temperature was varied from room temperature to 675 K. Gold films for making ohmic contact were evaporated on the two ends of the film on the substrate, which worked BS electrodes. For illuminating the films, the tungsten filament incandescent lamp excited by 66 *

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Theory of high photovoltages in semiconducting films

Sosnowski

Orłowski

1970

Phys. Stat. Sol. (a)

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A theory of photo‐e.m.f. much exceeding the energy gap is given for various semiconducting films based on the assumption of periodicity of the film parameters. The equations describing space charge, transport, and generation‐recombination of current carriers are solved rigorously under periodic boundary conditions. The layer can be treated as an array of photocells, forming effectively an integrated circuit. Expressions for photovoltage are given and discussed in the limits of low and high illumination. Some integral inequalities being the conditions for the solutions to have a physical meaning are discussed. It is found that a phase shift between space charge and generation‐recombination distributions as functions of x is essential for the occurrence of high photovoltage. The space charge may be due either to charged donor and acceptor centres and occur already in dark or may be due to light induced trapped charge. Rise and decay of photovoltage are discussed and the possibility of obtaining fast effects is indicated.

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High Photovoltages in Cadmium Sulfide Films

Cited by 20 publications

References 19 publications

Phenomenological model of anomalously high photovoltages generated in obliquely deposited semiconductor films

Phenomenological model of anomalously high photovoltages generated in obliquely deposited semiconductor films

Photovoltaic effect in polycrystalline ZnTe films

Theory of high photovoltages in semiconducting films

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