Evaluation of Passivation Schemes of Large Area Si Solar Cells: Separating Serial Resistance from Other Losses by the CELLO Technique (original) (raw)
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World Conference on Photovoltaic Energy Conversion, 2012
120 µm thick multicrystalline Si solar cells with SiO/SiN stack rear-side passivation and Al point contacts are locally characterized using the CELLO technique. By combining different standard measurement modes-e.g. using different laser wavelengths, variation of global illumination intensity, and by measuring at different points along the I-V curve-effects due to parasitic shunting can be separated from other rear side effects like inhomogeneous surface passivation (i.e. due to stack or contacts) or series resistance. An increased series resistance at the rear side is found to improve the rear surface recombination behavior and thus induces a boost in the photocurrent response as an unexpected seemingly positive side effect. As a consequence the series resistance distribution of the rear side has to be taken into account for the correct interpretation of photocurrent data measured using light with long wavelengths.
A simple passivation technique for the edge area of silicon solar cells improves the efficiency
Solar Energy Materials and Solar Cells, 2002
The efficiency of silicon solar cells (SC) can strongly be degraded by localized defects especially at the edge of SC (e.g. scratches) which are introduced during the production of the SC and may cause local shunts. A new optimized chemical etching procedure has been developed which allows a very effective passivation of shunts at the SC edges without reducing the surface area, i.e. without a reduction of the I sc current. In contrast to other techniques like plasma etching ("coin staking") or cutting off the edges, this procedure could be implemented cheaply in a large scale production. The newly developed passivation method always leads to an improvement in the efficiency η of slightly or severely degraded SCs which is typically around 10%-30%, but can be as large as 100%, while good SCs are totally uneffected with respect to η while still showing an improvement of the leakage current.
Rear surface passivation for high efficiency silicon solar cells
2013
Symbol Description Unit E d Defect energy level eV ∆ Phase difference between the parallel and orthogonal electric field component Deg ∆n Excess electron concentration cm-3 ∆p Excess hole concentration cm-3 µ n Electron mobility cm 2 .V-1 s-1 µ p Hole mobility cm 2 .V-1 s-1 AM 1.5 Solar irradiance function versus wavelength for one sun intensity through the atmosphere with an incidence angle of 48.2° W.cm-2 B Radiative constant cm-3 .s-1
IEEE Journal of Photovoltaics, 2016
Laser firing processes have emerged as a technologically feasible approach to fabricate local point contacts or local doped regions in advanced high-efficiency crystalline-Si (c-Si) solar cells. In this work we analyze the local impact induced by the laser pulse on the passivation layers, which are commonly present in advanced c-Si solar cell architectures to reduce surface recombination. We use micro-photoluminescence (PL) measurements with a spatial resolution of 7 µm to evaluate the passivation performance at the surroundings of laser processed regions (LPRs). In particular, we have studied LPRs performed on SiCx/Al2O3and Al2O3-passivated c-Si wafers by an IR (1064 nm) laser. Micro-PL results show that passivation quality of c-Si surface is affected up to about 100 µm away from the LPR border, and that the extension of this damaged zone is correlated to the laser power and to the presence of capping layers. In the final part of the work, the observed decrease in passivation quality is included into an improved 3D simulation model that gives accurate information about the recombination velocities associated to the studied LPRs.
2013
The light-beam-induced current-based CELLO measurement technique (solar CELl LOcal characterization), originally developed for wafer-based silicon solar cells, can successfully be applied to thin-film solar cells, provided that contacting of a single cell is possible. This is shown exemplarily for several crystalline silicon on glass samples, having varying quality with respect to photocurrent extraction, series resistance, and power losses. For the latter, a comparison with results obtained from dark lock-in thermography gives quantitative agreement, provided that the cells are not severely shunted. V
Rear Passivation Schemes for Industrial Silicon Solar Cells
2008
This article deals with the problem of the contact between dielectric layers and aluminium on the rear side of solar cells and its impact on the passivation effect. Several dielectric layers and stacks of PECVD silicon nitride and silicon oxide have been deposited on monocrystalline and multicrystalline wafers to study their passivation behaviours. Solar cells were also elaborated with a dielectric/aluminium structure on the back side and a set of wafers was used to highlight the influence of aluminium capping dielectric layers on passivation. Although it is reported that all structures give similar passivations when composed of one layer of silicon nitride at least, capping them with aluminium degrades the passivation below the standard aluminium BSF except for the SiNr/SiN stacks which is only slightly degraded. Consequently, solar cells are not as good as full aluminium coverage cells and it is found that the minority carrier lifetime and the internal quantum efficiency results are in contradiction with the I (V) results. This fact entails the need of performing complete solar cells to study the rear passivation by dielectric layers.
Passivation of thin film silicon solar cells
2016
Passivation of thin film polycrystalline silicon solar cells in hydrogen plasma and in water vapour at various processing conditions to achieve maximum passivation effect. 2) In-situ analysis of the water vapour passivation process. 3) Analysis of the passivated solar cells by available methods to explain and describe mechanisms of the water vapour passivation process. 4) Comparison of the passivation in hydrogen plasma and in water vapour. Chapter 4 describes some of measuring methods used in this thesis Suns-VOC method, a sun simulator, EQE. Chapter 5 aims to present the state-of-the-art of solid phase crystallized (SPC) and liquid phase crystallized (LPC) thin film silicon solar cells, their structure, achieved results and perspectives. Chapter 6 researches optimum processing conditions of the water vapour passivation for SPC Si. Chapter 7 investigates a passivation effect of hydrogen plasma on SPC and LPC poly-Si solar cells. Chapter 8 reports on a possible synergetic passivation effect of water vapour and hydrogen plasma. Chapter 9 compares plasma hydrogenation and water vapour passivation. Chapter 10 presents optical pump transient terahertz probe spectroscopy as a useful tool for a contactless investigation of ultrafast processes in SPC Si solar cells. Chapter 11 brings a conclusion with the most important results and observations. Chapter 12 summarizes contributions of the thesis in the fields of silicon passivation and characterization. Chapter 13 presents further possible research steps in the field of silicon passivation processes and material characterization.
Production Technology for Passivation of Polycrystalline Silicon Solar Cells
2002
Techniques for cost-efficient operation of SiNx:H systems with a capability for hydrogen passivation in a manufacturing environment are analyzed. We conclude that SiNx:H performance may be optimized by a variety of techniques, and that the cost and productivity of the deposition tool may be the determining factors in the industries decision for a particular technique. PECVD constitutes the current benchmark.
Advances in surface passivation of c-Si solar cells
Materials for Renewable and Sustainable Energy, 2012
In order to avoid an unacceptably large efficiency loss when moving towards thinner silicon materials, the near-term challenge in the c-Si PV industry is to implement an effective passivation method for both cell surfaces. This paper discussed several suitable passivation schemes available. While the efficiency potential of industrially produced thin film poly-Si cells on foreign substrates cannot yet reliably be predicted, it is clear that wafer-based c-Si solar cells will allow to maintain (or even improve) today's efficiency levels while at the same time reducing the consumption of (expensive) crystalline silicon by up to 50 %. Given the trend towards these Si materials, the most promising surface passivation methods are identified to date. The key issues to be considered are cost-effectiveness, added complexity, additional benefits, reliability, and efficiency potential. The efficiency increase for best cells is around 0.5-0.6 %abs and the current efficiency potential already demonstrated for all technologies is around 19.0 %. Average efficiencies in industrial mass production for selected technologies are 18.5-18.6 % for Cz and 17.1 % for mc-Si.