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Journal ArticleDOI

Influence of Defects on Solar Cell Characteristics

TL;DR: In this article, the authors reviewed the present knowledge of the origin of non-ideal I-V characteristics of silicon solar cells and introduced new results on recombination involving coupled defect levels.
Abstract: The current-voltage (I-V) characteristics of most industrial silicon solar cells deviate rather strongly from the exponential behavior expected from textbook knowledge. Thus, the recombination current may be orders of magnitude larger than expected for the given material quality and often shows an ideality factor larger than 2 in a wide bias-range, which cannot be explained by classical theory either. Sometimes, the cells contain ohmic shunts although the cell’s edges have been perfectly insolated. Even in the absence of such shunts, the characteristics are linear or super-linear under reverse bias, while a saturation would be classically expected. Especially in multicrystalline cells the breakdown does not tend to occur at -50 V reverse bias, as expected, but already at about -15 V or even below. These deviations are typically caused by extended defects in the cells. This paper reviews the present knowledge of the origin of such non-ideal I-V characteristics of silicon solar cells and introduces new results on recombination involving coupled defect levels.

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Citations
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Journal ArticleDOI
TL;DR: In this paper, a method for in situ characterization of the photovoltaic module power at standard test conditions, using superposition of the dark I-V curve measured at the elevated stress temperature, during potential-induced degradation testing, avoiding stress transients while ramping to and from the stress temperature.
Abstract: We propose a method for in situ characterization of the photovoltaic module power at standard test conditions, using superposition of the dark current-voltage (I-V) curve measured at the elevated stress temperature, during potential-induced degradation (PID) testing. PID chamber studies were performed on several crystalline silicon module designs to determine the extent to which the temperature dependency of maximum power is affected by the degradation of the modules. The results using the superposition principle show a mismatch between the power degradation measured at stress temperature and the degradation measured at 25 °C, dependent on module design, stress temperature, and level of degradation. We investigate the correction of this mismatch using two maximum-power temperature translation methods found in the literature. For the first method, which is based on the maximum-power temperature coefficient, we find that the temperature coefficient changes as the module degrades by PID, thus limiting its applicability. The second method investigated is founded on the two-diode model, which allows for fundamental analysis of the degradation, but does not lend itself to large-scale data collection and analysis. Last, we propose and validate experimentally a simpler and more accurate maximum-power temperature translation method, by taking advantage of the near-linear relationship between the mismatch and power degradation. This method reduces test duration and cost, avoids stress transients while ramping to and from the stress temperature, eliminates flash testing except at the initial and final data points, and enables significantly faster and more detailed acquisition of statistical data for future application of various statistical reliability models. Potential-induced degradation chamber studies on crystalline silicon photovoltaic modules show a mismatch between the power degradation measured at stress temperature and the power degradation measured at 25 °C, which depends on module design, stress temperature, and level of degradation. We propose a method of in situ characterization of the photovoltaic module power at standard test conditions using superposition of the dark I-V curve measured at the elevated stress temperature during potential-induced degradation testing, avoiding stress transients while ramping to and from the stress temperature

42 citations


Cites background from "Influence of Defects on Solar Cell ..."

  • ...However, there are some limitations to the diode model, such as the case of industrial solar cells with manufacturing defects in which the dark I–V characteristic can deviate strongly from the textbook exponential behavior [18] and can be difficult to explain through the prism of the two-diode model....

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Proceedings ArticleDOI
19 Jun 2011
TL;DR: By evaluating dark lock-in thermography images taken at one reverse and three forward biases, images of all two-diode-parameters J 01, J 02, n 2 (ideality factor of J 02 ), and G p (the parallel ohmic conductivity) are obtained.
Abstract: By evaluating dark lock-in thermography images taken at one reverse and three forward biases, images of all two-diode-parameters J 01 , J 02 , n 2 (ideality factor of J 02 ), and G p (the parallel ohmic conductivity) are obtained. A local series resistance is explicitly considered and may be provided as a series resistance image, e.g. resulting from luminescence imaging. The results allow a separate investigation of factors influencing the depletion region recombination current and the bulk lifetime-governed diffusion current.

40 citations


Cites background from "Influence of Defects on Solar Cell ..."

  • ...The analysis of many global and local I–V characteristics of solar cells leads to n42 [3,4,6,9], which cannot be explained by standard point defect recombination theory....

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  • ...As discussed in [9], the origin of this recombination are mostly locally extended defects (including the edge) leading to a high local density of recombination states....

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  • ...It had been shown previously that ideality factors larger than two may be caused by recombination via extended defects [9]....

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Journal ArticleDOI
TL;DR: In this paper, the authors reported radial, p-n junction, sub-micrometre, pillar array textured solar cells, fabricated on an n-type Czochralski silicon wafer.
Abstract: We report radial, p–n junction, sub-micrometre, pillar array textured solar cells, fabricated on an n-type Czochralski silicon wafer. Relatively simple processing schemes such as metal-assisted chemical etching and spin on dopant techniques were employed for the fabrication of the proposed solar cells. Atomic layer deposition (ALD) grown aluminum oxide (Al2O3) was employed as a surface passivation layer on the B-doped emitter surface. In spite of the fact that the sub-micrometre pillar array textured surface has a relatively high surface-to-volume ratio, we observed an open circuit voltage (VOC) and a short circuit current density (JSC) as high as 572 mV and 29.9 mA cm−2, respectively, which leads to a power conversion efficiency in excess of 11.30%, for the optimized structure of the solar cell described herein. Broadband omnidirectional antireflection effects along with the light trapping property of the sub-micrometre, pillar array textured surface and the excellent passivation quality of the ALD-grown Al2O3 on the B-doped emitter surface were responsible for the enhanced electrical performance of the proposed solar cells.

36 citations

Journal ArticleDOI
TL;DR: Lower group V droplet supersaturations lead to a pure zincblende stacking-fault-free tip crystal structure, which improved the performance of a nanowire-based photovoltaic device.
Abstract: We describe methods of Ga droplet consumption in Ga-assisted GaAs nanowires, and their impact on the crystal structure at the tip of nanowires Droplets are consumed under different group V flux conditions and the resulting tip crystal structure is examined by transmission electron microscopy The use of GaAsP marker layers provides insight into the behavior of the Ga droplet during different droplet consumption conditions Lower group V droplet supersaturations lead to a pure zincblende stacking-fault-free tip crystal structure, which improved the performance of a nanowire-based photovoltaic device

31 citations

Journal ArticleDOI
TL;DR: In this paper, two approaches are proposed and compared for the characterization of edge losses in high-efficiency solar cells, and compared on heterojunction and passivated contacts solar cells.

26 citations

References
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Book
01 Jan 1974
TL;DR: In this article, a discussion is given of some aspects of the metal insulator transition and the status of the "minimum metallic conductivity" is discussed, and the concept is valid for liquids and in some, but not all, solid systems.
Abstract: A discussion is given of some aspects of the metal insulator transition. Particular attention is paid to the status of the “minimum metallic conductivity”. The concept is valid for liquids, and in some, but not all, solid systems.

2,109 citations

Journal ArticleDOI
01 Sep 1957
TL;DR: In this article, the authors show that the current due to generation and recombination of carriers from generation-recombination centers in the space charge region of a p-n junction accounts for the observed characteristics.
Abstract: For certain p-n junctions, it has been observed that the measured current-voltage characteristics deviate from the ideal case of the diffusion model. It is the purpose of this paper to show that the current due to generation and recombination of carriers from generation-recombination centers in the space charge region of a p-n junction accounts for the observed characteristics. This phenomenon dominates in semiconductors with large energy gap, low lifetimes, and low resistivity. This model not only accounts for the nonsaturable reverse current, but also predicts an apparent exp (qV/nkT) dependence of the forward current in a p-n junction. The relative importance of the diffusion current outside the space charge layer and the recombination current inside the space charge layer also explains the increase of the emitter efficiency of silicon transistors with emitter current. A correlation of the theory with experiment indicates that the energy level of the centers is a few kT from the intrinsic Fermi level.

1,934 citations


"Influence of Defects on Solar Cell ..." refers background or methods in this paper

  • ...It will be shown below that the characteristics of real solar cells behave very differently to the predictions of [2] because recombination in the depletion region contributes significantly to the cell’s total external current....

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  • ...This large ideality factor cannot be explained with classical diode theory, and also the J02 is about 3 orders of magnitude larger than expected by [2]....

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  • ...The classical theory of p-n junction diodes was established by Shockley [1] and was later extended by recombination in the p-n junction depletion region by Sah, Noyce, and Shockley [2]....

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  • ...According to [2] and also to recent, more realistic numerical simulations [3], J02 should be in the order of 10 A/cm(2) for relatively poor material with a excess carrier lifetime of  = 10 μs, and the ideality factor should be maximally n = 2....

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Book
01 Oct 1981
TL;DR: In this paper, the solar source of light energy is described and quantified, along with a review of semiconductor properties and the generation, recombination, and the basic equations of photovoltaic device physics.
Abstract: Solar cell theory, materials, fabrication, design, modules, and systems are discussed. The solar source of light energy is described and quantified, along with a review of semiconductor properties and the generation, recombination, and the basic equations of photovoltaic device physics. Particular attention is given to p-n junction diodes, including efficiency limits, losses, and measurements. Si solar cell technology is described for the production of solar-quality crystals and wafers, and design, improvements, and device structures are examined. Consideration is given to alternate semiconductor materials and applications in concentrating systems, storage, and the design and construction of standalone systems and systems for residential and centralized power generation. Bibtex entry for this abstract Preferred format for this abstract

1,773 citations


"Influence of Defects on Solar Cell ..." refers methods in this paper

  • ...It is common practice to include also these entities in a one- or two-diode model via an equivalent circuit [5]:...

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  • ...a one-diode model, for the approximation of the I-V characteristics [5]....

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Book
01 Oct 1991
TL;DR: In this article, a homogeneous semiconductor at equilibrium drift, diffusion, generation, recombination, trapping and tunneling metaloxide-semiconductor capacitor P/N and other junction diodes metal-oxide semiconductor and other field effect transistors bipolar junction transistor and other bipolar transistor devices.
Abstract: Electrons, bonds, bands and holes homogeneous semiconductor at equilibrium drift, diffusion, generation, recombination, trapping and tunneling metal-oxide-semiconductor capacitor P/N and other junction diodes metal-oxide-semiconductor and other field-effect transistors bipolar junction transistor and other bipolar transistor devices.

286 citations


"Influence of Defects on Solar Cell ..." refers background in this paper

  • ...Also modern textbooks such as Sah [4] describe the current-voltage (I-V) characteristic of solar cells on these theoretical grounds, which predicts that the reverse current-density saturates for a reverse bias below -100 mV to a constant value of -(J01 + J02)....

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  • ...The classical theory of p-n junction diodes was established by Shockley [1] and was later extended by recombination in the p-n junction depletion region by Sah, Noyce, and Shockley [2]....

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  • ...Also, the breakdown behavior of real (especially of MC) solar cells under reverse bias deviates significantly from the predictions in [4]....

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  • ...According to established theory, solar cells with a base doping concentration of 10(16) cm should break down by avalanche at a reverse bias above -50 V [4]....

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  • ...Advanced theory predicts avalanche breakdown above a certain reverse bias, which is below -50 V for typical solar cells having a base doping concentration of 10(16) cm [4]....

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