Light Intensity Exponents as Sensitive Tools for the Detection of Impurities in a-Si:H

2000 ◽  
Vol 609 ◽  
Author(s):  
L. F. Fonseca ◽  
S.Z. Weisz ◽  
P. Alpuim ◽  
V. Chu ◽  
J.P. Conde ◽  
...  
Keyword(s):  
Light Intensity ◽  
Temperature Dependence ◽  
Computer Simulations ◽  
Dominant Factor ◽  
State Distribution ◽  
Capture Coefficient ◽  
Yield Information ◽  
Recombination Processes ◽  
Minority Carriers ◽  
Forbidden Gap

ABSTRACTWe have shown recently that the temperature dependence of the phototransport properties can yield information regarding the state distribution in the forbidden gap of semiconductors. Of these properties the light intensity exponents of both, the majority carriers, γe, and the minority carriers, γh, were found to be very sensitive to the details of this distribution. In particular, noting that sub 1/2 values of the exponents are very unusual we have studied their origin in some a-Si:H materials. Finding experimentally such sub 1/2 values of γh and running computer simulations of the recombination processes in a-Si:H led us to the conclusion that these low values are due to acceptor-like centers which have a relatively high capture coefficient for the holes. We attribute these centers to the unintentional oxygen doping in a-Si:H. We will show that the oxygen presence, usually ignored in the discussions of the phototransport properties of a-Si:H, appears to be, in many cases, the dominant factor in the properties of “intrinsic” a-Si:H.

The Effect of Concentrated Light Intensity on Temperature Coefficient of the InGaP/InGaAs/Ge Triple-Junction Solar Cell

2015 ◽  
Vol 8 (1) ◽  
pp. 106-111 ◽  
Author(s):  
Zilong Wang ◽  
Hua Zhang ◽  
Wei Zhao ◽  
Zhigang Zhou ◽  
Mengxun Chen
Keyword(s):  
Solar Cell ◽  
Light Intensity ◽  
Temperature Dependence ◽  
Temperature Coefficient ◽  
Triple Junction ◽  
Concentration Ratio ◽  
Crystalline Silicon ◽  
Photovoltaic System ◽  
Solar Pv ◽  
Junction Solar Cell

Research on automatic tracking solar concentrator photovoltaic systems has gained increasing attention in developing the solar PV technology. A paraboloidal concentrator with secondary optic is developed for a three-junction GaInP/GalnAs/Ge solar cell. The concentration ratio of this system is 200 and the photovoltaic cell is cooled by the heat pipe. A detailed analysis on the temperature coefficient influence factors of triple-junction solar cell under different high concentrations (75X, 100X, 125X, 150X, 175X and 200X) has been conducted based on the dish-style concentration photovoltaic system. The results show that under high concentrated light intensity, the temperature coefficient of Voc of triple-junction solar cell is increasing as the concentration ratio increases, from -10.84 mV/°C @ 75X growth to -4.73mV/°C @ 200X. At low concentration, the temperature coefficient of Voc increases rapidly, and then increases slowly as the concentration ratio increases. The temperature dependence of η increased from -0.346%/°C @ 75X growth to - 0.103%/°C @ 200X and the temperature dependence of Pmm and FF increased from -0.125 W/°C, -0.35%/°C @ 75X growth to -0.048W/°C, -0.076%/°C @ 200X respectively. It indicated that the temperature coefficient of three-junction GaInP/GalnAs/Ge solar cell is better than that of crystalline silicon cell array under concentrating light intensity.

Temperature Dependence of the Decay of Optically Excited Charge Carriers in Amorphous Silicon

2003 ◽  
Vol 762 ◽  
Author(s):  
J. Whitaker ◽  
P. C. Taylor
Keyword(s):  
Temperature Dependence ◽  
Amorphous Silicon ◽  
State Density ◽  
Charge Carriers ◽  
Band Tail ◽  
Spin Resonance ◽  
Recombination Processes ◽  
Long Time ◽  
Tail Structure ◽  
Kinetics Of

AbstractWe report the temperature dependence of the growth and decay of the optically induced electron spin resonance (LESR) on short and long time scales (10-3 s < t < 2500 s). This range of times spans the region between previously published photoluminescence and the LESR data. In addition, we examine the steady-state density of optically excited charge carriers as a function of temperature. These measurements lead to a better understanding of the band tail structure of amorphous silicon as well as the kinetics of the excitation and recombination processes.

Temperature dependence of the resistance, impedance and capacitance of semitransparent PTB7-Th and PCBM sensor

2019 ◽  
Vol 33 (12) ◽  
pp. 1950110
Author(s):  
Muhammad Riaz ◽  
Khasan S. Karimov ◽  
Jameel-Un Nabi
Keyword(s):  
Light Intensity ◽  
Temperature Dependence ◽  
Temperature Sensor ◽  
Visual Control ◽  
Capacitance Measurement ◽  
Experimental Conditions ◽  
Temperature Resistance ◽  
Graphene Composite ◽  
Temperature Dependences ◽  
Resistance Coefficients

The temperature dependences of resistance, impedance and capacitance of semitransparent sensor having structure ITO/PTB7-Th:PC[Formula: see text]BM/Graphene composite (semisurface type) were investigated. The transparency of the sensor was 58–60%. The dependences of the resistance, impedance and capacitance at different frequencies 100 Hz, 1 kHz, 10 kHz, 100 kHz and 200 kHz and temperature in the range of 23.8–80[Formula: see text]C for the sensor were studied. It was observed that as the temperature increased from 23.8[Formula: see text]C to 80[Formula: see text]C, the resistance and impedance (at 1 kHz) of the samples decreased, on average, by a factor of 3.51 and 3.79, respectively. At same experimental conditions (1 kHz), the capacitances of the samples also decreased by a factor of 9.6. It was also noted that as frequency increased from 100 Hz to 200 kHz, the impedance of the sensor decreased by a factor of 21 and 12, at temperatures 24[Formula: see text]C and 58[Formula: see text]C, respectively. Under the same conditions, the capacitance decreased by a factor of 30 and 28, respectively. The temperature resistance coefficients were measured to be −1.31%/[Formula: see text]C, −1.30%/[Formula: see text]C, −1.27%/[Formula: see text]C, −0.84%/[Formula: see text]C, −0.72%/[Formula: see text]C and −0.33%/[Formula: see text]C for R, Z (100 Hz), Z (1 kHz), Z (10 kHz), Z (100 kHz) and Z (200 kHz), respectively. For capacitance measurement, the temperature capacitance coefficients were measured as −1.39%/[Formula: see text]C, −1.38%/[Formula: see text]C, −1.37%/[Formula: see text]C, −1.36%/[Formula: see text]C and −1.34%/[Formula: see text]C, respectively. The semitransparent PTB7-Th- and PC[Formula: see text]BM-based temperature sensor can be used for measurement of the temperature as a teaching aid in situations where visual control of illumination and light intensity is required.

Temperature Dependence of the O2-Oscillation Pattern in the Filamentous Cyanobacterium Oscillatoria chalybea and in Chlorella kessleri

1996 ◽  
Vol 51 (11-12) ◽  
pp. 823-832 ◽  
Author(s):  
K Burda ◽  
P He ◽  
K. P Bader ◽  
G. H Schmid
Keyword(s):  
Transition Temperature ◽  
Temperature Dependence ◽  
Oxygen Evolution ◽  
Filamentous Cyanobacterium ◽  
State Distribution ◽  
Oscillation Pattern ◽  
Chlorella Kessleri ◽  
Temperature Range ◽  
Oscillatoria Chalybea ◽  
Oxygen Evolving

Abstract Five characteristic discontinuities of the pattern of oxygen evolution have been detected for the filamentous cyanobacterium Oscillatoria chalybea in the temperature range of 0°C to 30°C. The temperatures at which these discontinuities occur are: ≈ 5°C, ≈ 11°C, ≈ 15°C, ≈ 21°C and ≈ 25°C. The calculated initial 5-S state distribution, the miss parameter and the fraction of the fast transition S3 → S0+ O2 are affected. The discontinuities are observed at the same transition temperature also for Chlorella kessleri hence are not specific for the cyanobacterium. Based on these studies it is concluded that the not vanishing oxygen signal under the first flash of a flash train in Oscillatoria cannot have its origin in interactions between oxygen-evolving complexes. A decrease of temperature should slow down the expected charge exchanges, improve the oscillations, thus reduce or lower the first two oxygen amplitudes of the oscillatoria pattern. Lowering of the temperautres improves the oscillations but does not lower the first O2 signal of the pattern.

Temperature dependence of open-circuit voltage and recombination processes in polymer–fullerene based solar cells

2011 ◽  
Vol 95 (8) ◽  
pp. 2131-2135 ◽  
Author(s):  
Anil K. Thakur ◽  
Guillaume Wantz ◽  
Germà Garcia-Belmonte ◽  
Juan Bisquert ◽  
Lionel Hirsch
Keyword(s):  
Solar Cells ◽  
Temperature Dependence ◽  
Open Circuit Voltage ◽  
Open Circuit ◽  
Recombination Processes

Local Microflow Control Using Photothermal Viscosity Distribution

2008 ◽  
Author(s):  
Jun Shimakawa ◽  
Masahiro Motosuke ◽  
Shinji Honami
Keyword(s):  
Laser Beam ◽  
Temperature Dependence ◽  
Temperature Rise ◽  
Local Heating ◽  
Velocity Variation ◽  
Dominant Factor ◽  
Photothermal Effect ◽  
Strong Temperature Dependence ◽  
Velocity Change ◽  
Micro Piv

A novel method of microflow control by locally heated liquid using an optical technique is described in this paper. Microflow control in the present study utilizes temperature dependence of the fluid property which becomes dominant in microscale. Since it is known that viscosity has strong temperature dependence, a local viscosity distribution has a potential to change microflow behavior. The purpose of the present study is to validate this concept of microflow control by using the local distribution of viscosity. In order to induce the temperature variation, photothermal effect is utilized. Absorption of a laser beam causes the local heating spot. This method has attractive features such as non-intrusive and high time- and spatial- resolution, and also has a possibility for a flexible flow control. We have developed an experimental system to irradiate focused laser beam on a flow in a microfluidic device and to measure velocity and temperature field of the microflow. The local temperature rise in microchannel flow is generated by a focused laser spot. During the laser irradiation, the velocity profile of the liquid flow in microchannel with 500 μm in width and 50 μm in height was measured by micro-PIV (Particle Image Velocimetry). The temperature measurement of the flow field was performed by micro-LIF (Laser-Induced Fluorescence). Around the heated area, the local increase of the flow velocity can be observed. It is found that the effect depends on the laser intensity and is independent of the bulk velocity. In addition, numerical simulation was conducted to identify the dominant factor causing the velocity change. As a simulation result, the cause of the velocity variation is the viscosity decrease corresponding to the temperature rise in fluid. Possibility of microflow control using the photothermal viscosity distribution is confirmed.

A Propos de la Création de Photoporteurs à Partir d'Excitons dans CdS

1971 ◽  
Vol 49 (14) ◽  
pp. 1967-1970 ◽  
Author(s):  
A. Coret ◽  
H. L. Malm
Keyword(s):  
Light Intensity ◽  
Photoconductivity Spectrum ◽  
Free Carriers ◽  
Recombination Processes ◽  
The Creation

According to the variation of the photoconductivity spectrum of CdS with light intensity it appears that excitons do not play a role in the recombination processes of photocarriers. Excitons first dissociate and give free carriers. The existence of maxima of photocurrent is related to the creation of photocarriers near the surface.

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