Analysis Of Silicon Solar Cells Research Articles

Opto-electro-thermal simulation of heat transfer in monocrystalline silicon solar cells

AbstractIn the area of photovoltaics, monocrystalline silicon solar cells are ubiquitously utilized in buildings, commercial, defense, residential, space, and transportation applications throughout the world. Their performance is impeded by the heating of the cells during their interaction with the incident solar radiation. The development of reliable computer simulations that effectively model the thermal response of monocrystalline silicon solar cells is critical for their design, fabrication, and utilization. This work employs a novel computer simulation to incorporate the optical, electrical, and thermal properties of silicon in the thermal analysis of silicon solar cells. After establishing the theoretical principles and the values of these properties, the results of the simulation are compared with other established studies. The analysis shows that the percentage difference in solar cell temperatures between simulation and literature is within a range of 0.354–0.487%. The proposed simulation shows that the visible range of wavelengths is the dominant source of heating in commercial monocrystalline silicon solar cells.

Failure Analysis of Silicon Solar Cells in the Presence of Cracks: Correlated to Partial Shading

Failure Analysis of Silicon Solar Cells in the Presence of Cracks: Correlated to Partial Shading

Device Parameter Extraction for Loss Analysis of Silicon Solar Cells Based on Intelligent Model Fitting

A fully automated and rigorous loss analysis routine that provides a breakdown of the loss components occurring in silicon solar cells is presented in this work. The routine combines large-area two-dimensional modeling and smart auto-fitting routines with luminescence imaging. This allows the spatially resolved information in luminescence images to be analyzed to extract recombination parameters partitioned by regions (e.g. wafer edge, under metal contacts, over passivated areas), as well as the spatial distribution of contact resistance. After these cell parameters have been extracted, a loss analysis of open-circuit voltage can be performed by simulating the open-circuit condition and examining the various recombination currents, and a loss analysis of fill factor can be performed by successively turning off the effects of factors that degrade it in simulation. The technique is demonstrated on a multicrystalline silicon PERC solar cell.

The reliability of thermography- and luminescence-based series resistance and saturation current density imaging

The conventional quantitative evaluation of dark lock-in thermography (DLIT), electroluminescence (EL), and photoluminescence (PL) images of solar cells is based on the model of independent diodes, where each image pixel is assumed to be connected with the terminals by an independent series resistance. In reality, however, the solar cell represents a 2-dimensional resistance-diode network. In this work solar cells containing well-defined spatial distributions of the saturation current density J01 and also containing J02-type and ohmic shunts are modeled for various externally applied biases and illumination conditions realistically as a 2-dimensional resistance-diode network. The resulting local diode voltage distributions are converted into DLIT, EL and PL images, which are further processed by conventional evaluation methods, which rely on the simple model of independent diodes. These are the so-called “Local-IV” method for the DLIT analysis, which may be supported by EL results to obtain series resistance images, and “C-DCR” for the PL analysis. This leads to calculated images of the local effective series resistance Rs and of J01. Regarding the resulting Rs images, PL shows the expected series resistance distribution and is not affected by the shunt regions. The DLIT–EL Rs images instead yield expected values only in the homogeneous regions, which are not affected by the assumed shunts. DLIT–EL determines higher values of Rs in local shunt regions and lower values around these regions and in spatially extended shunt regions. Regarding the J01 images both methods again give the expected results if J01 is distributed homogeneously. However, in the shunted regions, PL suffers from balancing currents within the emitter and DLIT from optical blurring. By comparing local and extended regions of increased J01 we find that DLIT approximates the expected J01 value better than PL, which clearly underestimates even extended local maxima of J01. For a local current analysis of silicon solar cells we recommend the use of DLIT for the determination of J01 images and PL for the determination of Rs images.

Opto-electronic analysis of silicon solar cells by LBIC investigations and current–voltage characterization

A different laser beam induced current (LBIC) mapping technique has been used for the measurements of spatial variation of light generated current of a solar cell. These variations are caused by parasitic resistances and defects at grain boundaries (GBs) in multicrystalline silicon solar cells (mc-Si). This study investigates and identifies the regions within mc-Si solar cells where dominating recombination and lifetime limiting processes occur. A description of the LBIC technique is presented and the results show how multicrystalline GBs and other defects affect the light generated current of a spot illuminated mc-Si solar cell. The results of the internal quantum efficiency (IQE) at wavelength of 660 nm revealed that some regions in mc-Si solar cell give rise to paths that lead current away from the intended load.

Lifetime analysis of silicon solar cells by microwave reflection

Microwave photoconductive decay ( μPCD) has become a standard technique for measuring the carrier lifetime of silicon used in solar cells. Here, we have used μPCD to examine the carrier lifetimes at common doping levels used in the base region of silicon photovoltaic devices. For the conductivity range used in the p-type base of n +–p structures, the microwave penetration depth is less than the wafer thickness. In this case, the reflectance–conductivity relationship is very nonlinear. We will show that quasi-steady-state photoconductivity (QSSPC) and resonance-coupled photoconductive decay (RCPCD) lifetime measurements track over a wide range of injection level, and generally agree at higher injection levels. Our μPCD data will be compared with the transient RCPCD data over the same range. The data from the latter agree at low-injection levels, but show serious disagreement at higher injection levels. The conclusion is that μPCD must be limited to low-injection levels in the doping range used for solar cells.

An alternative method for the performance analysis of silicon solar cells

An approximate formula for electron-hole generation rate has been proposed. The proposed approximation is found to give good representation of the actual generation rate provided by Dunbar and Hauser and by Fossum. In order to determine the applicability of this approximation attempts have been made to calculate short-circuit current, open-circuit voltage, and solar cell efficiency of an n+p silicon solar cell. The calculations involve consideration of nonuniform doping, spatial dependence of the band, and drift field for the n+ region, and band gap narrowing, Shockley–Read–Hall recombination, and Auger recombination for both n+ and p regions. The variations of short-circuit current, open-circuit voltage, and solar cell efficiency with doping concentration of the substrate p region are found to be in good agreement with results obtained from experiments. The trend of the results indicates that proper optimization of the width and impurity concentration of the diffused n region, of the width and impurity concentration of the substrate p region, and of the front-surface recombination velocity is necessary for achieving the highest efficiency of a solar cell.

A new method of analyzing the short-circuit current of silicon solar cells

New approximations for the carrier generation rates in silicon under AM1 and AM2 solar illumination are presented. They may simplify the analysis of silicon solar cells, particularly when done by hand.

Analysis of silicon solar cells with stripe geometry junctions

Silicon solar cells with stripe geometry junctions are analyzed. The base region collection efficiency is found to be insensitive to the transmissivity of the electrode and/or the diffused layer but quite sensitive to the width and separation of the stripe junctions. The additional losses of carriers are mainly due to the increased bulk recombination rather than the surface recombination. In one case analyzed the collection efficiency decreases by 22% when the junctions are separated by about one sixth of the diffusion length with the surface recombination velocity at 300 cm/sec. Possible uses of the stripe-junction design in p- n junction cells and Schottky barrier cells are re-examined in the light of the new calculation and found to be less attractive than previously suggested.

Analysis of Silicon Solar Cells with Multi-Layer Structure

The multi-layer silicon solar cells have been theoretically analyzed at AM 0 by a simplified one dimentional first order solar cell model, which neglects depletion region recombination, high injection and drift currents. It is shown that the six-layer solar cell is an optimum structure. The six-layer solar cell is compared with the conventional p+-n solar cell and the back-surface field (BSF) p+-n-n+ solar cell. It is proven that the multi-layer solar cells can show still higher conversion efficiencies than the BSF solar cell and the conversion efficiency can approach about 21% at AM 0.