Elecrically Detected Magnetic Resonance in A-SI:H Pin Cells

1993 ◽  
Vol 297 ◽  
Author(s):  
Klaus Lips ◽  
Walther Fuhs
Keyword(s):  
Solar Cells ◽  
Magnetic Resonance ◽  
Dark Current ◽  
Defect Density ◽  
Light Exposure ◽  
Forward Bias ◽  
Internal Field ◽  
Exciting Light ◽  
Applied Bias ◽  
Forward Current

We report on a detailed study of EDMR in pin-type solar cells. Like in films the signals are dominated by the contribution of the e-db resonance. It is found that the spectra depend on the applied bias and photon energy of the exciting light. The data suggest that the dark current is controlled by recombination in the bulk of the i-layer. The sign of the signal depends sensitively on the sign of the internal field. At high forward bias and illumination recombination at the pi-interface plays an important role. Degradation by both light exposure and high forward current results predominantly from an increase of the bulk defect density.

scholarly journals Mechanisms of charge accumulation in the dark operation of perovskite solar cells

2016 ◽  
Vol 18 (22) ◽  
pp. 14970-14975 ◽  
Author(s):  
Teresa S. Ripolles ◽  
Ajay K. Baranwal ◽  
Koji Nishinaka ◽  
Yuhei Ogomi ◽  
Germà Garcia-Belmonte ◽  
...  
Keyword(s):  
Solar Cells ◽  
Dark Current ◽  
Forward Bias ◽  
Perovskite Solar Cells ◽  
Charge Accumulation ◽  
Current Voltage

In this work, a new current peak at forward bias in the dark current–voltage curves has been identified for standard mesoscopic perovskite solar cells.

scholarly journals Measurement and modelling of dark current decay transients in perovskite solar cells

2017 ◽  
Vol 5 (2) ◽  
pp. 452-462 ◽  
Author(s):  
Simon E. J. O'Kane ◽  
Giles Richardson ◽  
Adam Pockett ◽  
Ralf G. Niemann ◽  
James M. Cave ◽  
...  
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Dark Current ◽  
Perovskite Solar Cells ◽  
Sudden Change ◽  
Perovskite Solar Cell ◽  
Applied Bias ◽  
Current Decay

The current decay in response to a sudden change of applied bias up to 1 V has been measured on a methylammonium lead triiodide perovskite solar cell, for temperatures between 258 and 308 K.

Internal Electric Field Profile in Thin Film Hydrogenated Amorphous Silicon Diodes Studied by the Transient-Null-Current Method

1997 ◽  
Vol 467 ◽  
Author(s):  
Daxing Han ◽  
Chenan Yeh ◽  
Keda Wang ◽  
Qiwang
Keyword(s):  
Solar Cells ◽  
Electric Field ◽  
Space Charge ◽  
Forward Bias ◽  
Current Method ◽  
Internal Field ◽  
Total Charge ◽  
Internal Electric Field ◽  
Field Profile ◽  
Electric Field Profile

ABSTRACTWe demonstrate that the internal field of a thin a-Si:H pin solar cells can be measured using the transient-null-current method. This method was previously developed to measure the internal field profile in a-Si alloy Schottky barrier. The internal electric field profile was determined by measuring the forward-bias voltages that tune the transient photocurrents generated by a pulsed laser at a various wavelengths to zero. We adopt the same technique to a-Si:H p-i-n solar cells. In the case of p-i-n structure, we need to consider both space charge contributed by photogenerated carriers and carrier recombination which disturb the internal field. We use two critical conditions to minimize these effects. (1) To limit the contribution of photocarriers to space-charge distribution, the total charge collected is less than 10−10 C per pulse, and a repetition rate 1 Hz is used to ensure that the diode remains close to its equilibrium state. (2) The measuring time window is about 1 – 6 μs following the displacement current. Typically the RC constant of diode is < 1 μs and the rise time of the forward-bias recombination current is 6.0 × μs. We apply the signal average to process the forward-bias voltage. The error is within ± 0.05 V. With this technique we can study the effect of variety of structure design or processing on the device performance.

Illumination Dependence of Microcrystalline PIN Diodes

2001 ◽  
Vol 664 ◽  
Author(s):  
Torsten Brammer ◽  
Franz Birmans ◽  
Mathias Krause ◽  
Helmut Stiebig ◽  
Heribert Wagner
Keyword(s):  
Solar Cell ◽  
Ideality Factor ◽  
Dark Current ◽  
Defect Density ◽  
Short Circuit ◽  
Forward Bias ◽  
Microcrystalline Silicon ◽  
Defect States ◽  
Solar Cell Performance ◽  
Recombination Centers

ABSTRACTNumerical simulations of the current-voltage characteristics of PECVD-microcrystalline silicon based p-i-n diodes were performed to study the affect of defect density and mobility on solar cell performance. Depending on the combination of both parameters the ideality factor increases or decreases with applied forward bias. The reason is the variable contribution of volume recombination to the total diode current and space charge stored in defect states. The decrease in dark current with reduced hydrogen dilution can partly be attributed to a decrease in recombination centers by the same factor as predicted for midgap defect states by the analytic diode theory. Microcrystalline silicon solar cells deposited in the highly crystalline regime (high H-dilution) are limited by recombination of photogenerated carriers and high dark current. Both can be attributed to a large number of recombination centers. The fill factor of our state-of-theart solar cell is limited by the dark current for small illumination intensities, by series resistance for high illumination levels and by both at its maximum under AM1.5 illumination. Short-circuit current and open-circuit voltage pairs measured under intensities from 10-6 to 30 suns reveal a diode characteristic corresponding to an ideality factor of one at large forward bias.

Conduction-Band-Offset Rule Governing J-V Distortion in CdS/CI(G)S Solar Cells

2005 ◽  
Vol 865 ◽  
Author(s):  
A. Kanevce ◽  
M. Gloeckler ◽  
A.O. Pudov ◽  
J.R. Sites
Keyword(s):  
Solar Cells ◽  
Solar Cell ◽  
Conduction Band ◽  
Defect Density ◽  
Forward Bias ◽  
Window Layer ◽  
Band Offset ◽  
Type I ◽  
Current Collection ◽  
Conduction Band Offset

AbstractA type-I (“spike”) conduction-band offset (CBO) greater than a few tenths of an eV at the n/p interface of a solar cell can lead to significant distortion of the current-voltage (J-V) curve. Such distortion has been observed in CdS/CIS cells, low-gallium CdS/CIGS cells, and CIGS cells with alternative windows that increase the CBO. The basic feature is reduced current collection in forward bias. The distortion is mitigated by photoconductivity in the CdS or other window layer, and it is therefore more severe if the illumination contains no photons with energies greater than the band gap of the window layer. The device-physics analysis of such distortion is numerical simulation incorporating a three-layer [TCO/CdS/CI(G)S] approximation for the solar cell. The parameters that influence the barrier height, and hence the distortion, are the magnitude of the CBO, the doping of the p- and n- layers, the defect density of the CdS, and the thicknesses of the CdS and TCO layers. The key value, however, is the energy difference between the quasi-Fermi level for electrons and the conduction band at the CdS/CIS interface. Thermionic emission across the interface will limit the current collection, if the difference exceeds approximately 0.48 eV at 300 K and one-sun illumination. This constraint is consistent with experiment, and strategies to satisfy the 0.48-eV rule when designing solar cells are enumerated.

Spin-Dependent Recombination Effects in a-SI:H Pin Solar Cell Devices: A New Characterization Technique

1995 ◽  
Vol 377 ◽  
Author(s):  
Klaus Lips
Keyword(s):  
Solar Cell ◽  
Defect Density ◽  
Internal Field ◽  
Operating Conditions ◽  
Recombination Rates ◽  
Resonant Enhancement ◽  
Forward Current ◽  
Standard Operating ◽  
Electrically Detected Magnetic Resonance ◽  
Dependent Processes

ABSTRACTElectrically detected magnetic resonance (EDMR) - also often referred to as spin-dependent photoconductivity - is a particularly attractive technique for the investigation of the electronic properties of semiconductor devices. This method detects the paramagnetic states involved in transport and recombination by recording changes of the sample current induced by a resonant enhancement of the recombination rates. This is in contrast to ESR which monitors the resonant enhancement of microwave absorption. Therefore, EDMR is more sensitive by many orders of magnitude than conventional ESR and can be used to investigate a-Si:H solar cell devices under standard operating conditions.In this report we review the EDMR technique and discuss, in detail, the spin-dependent processes controlling dark and photocurrent of standard a-Si:H pin solar cells. In particular, we show that EDMR is sensitive to changes in the internal field of the i layer. We compare the experimental results to numerical calculations of the potential profiles and of EDMR-related quantities. We arrive at the conclusion that degradation by both high forward current and illumination increases the defect density mainly in the i layer, rather than at the pi interface.

Microcrystalline (Si,Ge):H Solar Cells

2003 ◽  
Vol 762 ◽  
Author(s):  
Jianhua Zhu ◽  
Vikram L. Dalal
Keyword(s):  
Solar Cells ◽  
Buffer Layer ◽  
Quantum Efficiency ◽  
Fill Factor ◽  
Open Circuit Voltage ◽  
Defect Density ◽  
Cell Structure ◽  
Open Circuit ◽  
Base Layer ◽  
Ecr Plasma

AbstractWe report on the growth and properties of microcrystalline Si:H and (Si,Ge):H solar cells on stainless steel substrates. The solar cells were grown using a remote, low pressure ECR plasma system. In order to crystallize (Si,Ge), much higher hydrogen dilution (∼40:1) had to be used compared to the case for mc-Si:H, where a dilution of 10:1 was adequate for crystallization. The solar cell structure was of the p+nn+ type, with light entering the p+ layer. It was found that it was advantageous to use a thin a-Si:H buffer layer at the back of the cells in order to reduce shunt density and improve the performance of the cells. A graded gap buffer layer was used at the p+n interface so as to improve the open-circuit voltage and fill factor. The open circuit voltage and fill factor decreased as the Ge content increased. Quantum efficiency measurements indicated that the device was indeed microcrystalline and followed the absorption characteristics of crystalline ( Si,Ge). As the Ge content increased, quantum efficiency in the infrared increased. X-ray measurements of films indicated grain sizes of ∼ 10nm. EDAX measurements were used to measure the Ge content in the films and devices. Capacitance measurements at low frequencies ( ~100 Hz and 1 kHz) indicated that the base layer was indeed behaving as a crystalline material, with classical C(V) curves. The defect density varied between 1x1016 to 2x1017/cm3, with higher defects indicated as the Ge concentration increased.

High-Irradiance Degradation Studies of Metamorphic 1eV GaInAs Solar Cells

2012 ◽  
Vol 1432 ◽  
Author(s):  
Ryan M. France ◽  
Myles A. Steiner
Keyword(s):  
Solar Cells ◽  
Active Region ◽  
Dislocation Density ◽  
Dark Current ◽  
Degradation Mechanism ◽  
Control Cell ◽  
High Irradiance ◽  
Threading Dislocation ◽  
Threading Dislocation Density ◽  
Degradation Studies

ABSTRACTInitial tests are performed regarding the degradation of lattice-mismatched GaInAs solar cells. 1eV metamorphic GaInAs solar cells with 1-2×106 cm-2 threading dislocation density in the active region are irradiated with an 808 nm laser for 2 weeks time under a variety of temperature and illumination conditions. All devices show a small degradation in Voc that is logarithmic with time. The absolute loss in performance after 2 weeks illuminated at 1300 suns equivalent and 125°C is 7 mV Voc and 0.2% efficiency, showing these devices to be relatively stable. The dark current increases with time and is analyzed with a two-diode model. A GaAs control cell degrades at the same rate, suggesting that the observed degradation mechanism is not related to the additional dislocations in the GaInAs devices.

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