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Chen Y.,Sun Yat Sen University | Chen Y.,Leibniz University of Hanover | Shen H.,Sun Yat Sen University | Shen H.,TRINA SOLAR LTD | Altermatt P.P.,Leibniz University of Hanover
Solar Energy Materials and Solar Cells | Year: 2014

The Al-alloyed back surface field (Al-BSF) is a current topic in research and development of crystalline Si solar cells for mass production. We simulate the solar cells in full-size with numerical device modeling, based on incomplete ionization and updated parameters of the Al-O complex in the Al-BSF region, combined with SPICE circuit models. The simulations show that for full-area rear contact, the full-area Al-BSFs should optimally be about 6 μm deep; in shallower Al-BSFs, recombination at the metal contact dominates; and in deeper Al-BSFs, recombination via Al-O defects dominates. The recombination in the Al-BSF dominates the cell's total recombination in well optimized cells. The optimally attainable cell efficiency then is about 18.8% after degradation of the B-O complex in the boron-doped wafer, or 19.1% after deactivating the B-O complexes as completely as currently possible. In PERC cells, having screen-printed Al-BSF fingers and a rear Al2O3 passivation layer, cell efficiency reaches about 19.6% or 20.3% after degradation or deacivation, respectively, with an improved homogeneous emitter that is feasible for mass production, and with screen-printing front contacts. Ideally, the design strategies for PERC structure with various wafer resistivities and rear finger widths are shown. The reduction in cell efficiency due to three different types of voids (cavities) in local Al-BSFs is also quantified in detail. © 2013 Elsevier B.V.

Zeng L.,Sun Yat Sen University | Li M.,Sun Yat Sen University | Chen Y.,Sun Yat Sen University | Chen Y.,TRINA SOLAR LTD | Shen H.,Sun Yat Sen University
Solar Energy | Year: 2014

This paper investigates the impact of SiO. xN. y/SiN. x:H double layer antireflection (DLAR) coatings on color modulation and cell efficiencies of multicrystalline silicon (mc-Si) solar cells. We presented a three dimensional ellipsoid surface model to simulate the concave-like morphology formed by acidic texturization. Afterwards, reflectivities of these acidic textures coated by DLAR coatings over 300-1100. nm are calculated by Monte Carlo ray tracing method. Simulated results show that DLAR coatings can flexibly modulate the color with reduced current losses compared to single SiN. x:H layer. SiO. xN. y was deposited by electron beam evaporation onto fabricated industrial solar cells to vary their colors. The busbars were sheltered by a mask to prevent the deposition of SiO. xN. y on them. This simplified method avoids adjustment of the standard fabricating process. High agreement between simulated and measured reflectance is achieved. The IV test results of colored solar cells are in good accord with the calculated results, which indicates the effectiveness of DLAR coatings in reducing the current losses. © 2014 Elsevier Ltd.

Tao W.,TRINA SOLAR LTD | Du Y.,Zhejiang University of Technology
Solar Energy | Year: 2015

In this work we investigate how the optical properties of monocrystalline silicon and polycrystalline silicon wafers are affected by texturing techniques and encapsulation. For monocrystalline wafers, the KOH etching is better than acid etching while reactive ion etching (RIE) is proven to be preferred compared to acid etching for polycrystalline wafers. The differences in reflectance (R) between two textures are apparent before encapsulation, but when the textured wafers are encapsulated with glass especially antireflectance coated (ARC) glass, the difference can be reduced from about five percentage points to below a percentage point. More important, the optical losses caused by reflectance (R) losses and parasitic absorption losses (A) for four types of commercial monocrystalline and polycrystalline silicon module are quantified and compared. Analyses are carried out for eight configurations using a stratified model consisting of solar cell wafers as well as cover glass and ethylene vinyl acetate (EVA). The model is to first obtain the external reflectance (R) and transmittance (T) in each layer, and the spectrally parasitic absorption loss associated with the cover glass and EVA is calculated with the aid of R and T measurements, which allows us to do a complete optical loss analysis for the solar module. The results show that the KOH texture with ARC glass encapsulation may be better choice for monocrystalline wafers, which gives a 94.04% of effective light collected by silicon. The RIE technique with ARC glass is suitable for polycrystalline substrates with excellent light trapping of 94.14%. After all, reflectance from glass surface and silicon surface accounts for over 70% of total loss, while the absorption of glass and EVA accounts for the rest and less loss. © 2015 Elsevier Ltd.

Sio H.C.,Australian National University | Xiong Z.,TRINA SOLAR LTD | Trupke T.,BT Imaging Pty Ltd | Macdonald D.,Australian National University
Applied Physics Letters | Year: 2012

We present a method for monitoring crystal orientations in chemically polished and unpassivated multicrystalline silicon wafers based on band-to-band photoluminescence imaging. The photoluminescence intensity from such wafers is dominated by surface recombination, which is crystal orientation dependent. We demonstrate that a strong correlation exists between the surface energy of different grain orientations, which are modelled based on first principles, and their corresponding photoluminescence intensity. This method may be useful in monitoring mixes of crystal orientations in multicrystalline or so-called "cast monocrystalline" wafers. © 2012 American Institute of Physics.

Trina Solar Ltd | Date: 2011-10-21

A method of fabricating an all-back-contact (ABC) solar cell, and an ABC solar cell. The method comprises the steps of forming respective pluralities of different polarity rear side doped regions on a wafer; forming an insulating layer on the doped regions; and forming conducting bars on the insulating layer such that each conducting bar is in electrical contact with different ones of the doped regions of the same polarity.

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