Solar Cell Manufacturing Process Research Articles

Focus on lasers and imaging

Focus on lasers and imaging

Determination of the specific shunt resistances under and away from the front contacts of solar cell

New structure of front contacts was devised and fabricated for accurately measuring the resistances under and away from the front contacts of silicon solar cell with the results showing that the former was much worse. The sample preparing sequence was completely compatible with the conventional solar cell manufacturing process, which demonstrated the convenience of this approach. With the aid of this characterization technique, detailed information can be obtained on the solar cell structure, material ingredients and process parameters, especially the sintering process.

Optimise your solar cell manufacturing process

Optimise your solar cell manufacturing process

High-efficiency solar cells on phosphorus gettered multicrystalline silicon substrates

Measurements of the dislocation density are compared with locally resolved measurements of carrier lifetime for p-type multicrystalline silicon. A correlation between dislocation density and carrier recombination was found: high carrier lifetimes (>100 µs) were only measured in areas with low dislocation density ( 106 cm−2) relatively low lifetimes (<20 µs) were observed. In order to remove mobile impurities from the silicon, a phosphorus diffusion gettering process was applied. An increase of the carrier lifetime by about a factor of three was observed in lowly dislocated regions whereas in highly dislocated areas no gettering efficiency was observed. To test the effectiveness of the gettering in a solar cell manufacturing process, five different multicrystalline silicon materials from four manufacturers were phosphorus gettered. Base resistivity varied between 0·5 and 5 Ω cm for the boron- and gallium-doped p-type wafers which were used in this study. The high-efficiency solar cell structure, which has led to the highest conversion efficiencies of multicrystalline silicon solar cells to date, was used to fabricate numerous solar cells with aperture areas of 1 and 4 cm2. Efficiencies in the 20% range were achieved for all materials with an average value of 18%. Best efficiencies for 1 cm2 (20·3%) and 4 cm2 (19·8%) cells were achieved on 0·6 and 1·5 Ω cm, respectively. This proves that multicrystalline silicon of very different material specification can yield very high efficiencies if an appropriate cell process is applied. Copyright © 2006 John Wiley & Sons, Ltd.

Industrial manufacturing of semitransparent crystalline silicon POWER solar cells

This paper gives an extract of the state of the art of the manufacturing of semitransparent crystalline silicon POWER solar cells in an industrial environment. A short introduction of the POWER devices concept (see Fig. 1) will be given followed by an insight in the applied production process. Finally, examples effecting the efficiency distribution in the cell production and their solutions are given. It is believed that the lessons we learned in optimising the manufacturing process and production line of transparent POWER solar cells can be helpful for the increasing activities in the direction of thin wafers as well as novel solar cell devices.

Low-cost multicrystalline back-contact silicon solar cells with screen printed metallization

Abstract Adaptation to market requirements is a permanent challenge in industrial solar-cell production. Both increase of cell efficiency as well as lowering costs is demanded. Back-contacted solar cells offer multiple advantages in terms of reducing module assembling costs and enhanced cell efficiency. The investigated emitter-wrap-through (EWT) design [1] has a collecting emitter on front and rear side. These emitter areas are electrically connected by small holes. Due to the double-sided collecting junction, this cell design is favourable for materials with a low-minority charge carrier diffusion length leading to a higher short circuit current density. Untill now most investigations on EWT solar cells were performed on Cz or even FZ silicon. This was justified as long as different processing techniques had to be developed and compared. But as an industrially applicable process sequence has recently been developed [2] , the advantages of the EWT concept compared to conventionally processed cells have to be shown on multicrystalline material. In the following, a manufacturing process of EWT solar cells is presented which is especially adapted to the requirements of multicrystalline silicon. Effective surface texturization was reached by mechanical V-texturization and bulk passivation by a hydrogen plasma treatment. The efficiency of the best solar cells within this process reached 14.2% which is the highest efficiency reported so far for mc-Si 10×10 cm 2 EWT solar cells [3] .

On the effects of tilted light in a global prediction of AlGaAs/GaAs solar cell performance

A global optimisation of AlGaAs/GaAs solar cells under light with different angles of incidence is carried out in this work. Not only are the optimum internal and external device structures calculated, but also the thicknesses of the anti-reflecting coatings layers. For this reason, a study of the whole structure is carried out from a global point of view taking state-of-the-art technology into account. In fact, this kind of work has not been carried out up till now. The best structure, working at 1000 suns (100 W/cm 2), reaches an efficiency of 28.8% for normal incidence of light. This efficiency is nearly constant up to an incident angle of around 60° and it then sharply decreases for higher angles. Variations of parameters that can be optimised (thicknesses and doping levels) as a function of angle of incidence ranging from 0° to 90° are presented. Deviations from the optimum structure are also analysed with the purpose of determining their influence in the solar cell manufacturing process.

Low-cost back contact silicon solar cells

Back-contacted solar cells offer multiple advantages in regard of reducing module assembling costs and avoiding grid shadowing losses. The investigated emitter-wrap-through (EWT) device design has an electrical connection of the front emitter and the rear emitter grid in form of small holes drilled into the crystalline silicon wafer. The obtained cell structure is especially suitable for low-cost base material with small minority carrier diffusion lengths. Different industrially applicable solar cell manufacturing processes for EWT devices are described and compared. The latest experimental results are presented and interpreted; the photocurrent is found to be distinctly increased. The relation between open circuit voltage and rear side passivation is discussed based on two-dimensional (2-D) computer simulations.

Combining amorphous photovoltaics with new storage media to achieve low cost electricity through stand-alone systems

The scale-up of multi-junction, spectrum splitting, amorphous silicon alloy, thin-film photovoltaic devices has recently resulted in the demonstration of large area (1 foot square) modules with a stable energy conversion efficiency of 10.2%. It has also been demonstrated that these advanced modules can be produced in a low-cost, flexible roll-to-roll continuous web manufacturing process, and a roll-to-roll pilot production plant with a 2 MW annual production capacity for these modules has been constructed and installed. When mass produced light-weight, roof-mounted solar shingle modules employing the spectrum splitting cell design are combined with a new, long-life, energy storage system based on high performance and environmentally-safe nickel metal hydride batteries, stand-alone photovoltaic systems can be constructed with the capability of providing residential electricity at very low cost. As the production volume of both the battery and solar cell manufacturing process is increased, economies of scale can, for the first time, allow the cost of stand-alone solar electricity to approach the cost of grid-connected power in many locations.

Low Coherence Interferometry for Non-Invasive Semiconductor Monitoring

AbstractWe report on the first use of optical low coherence reflectometry (OLCR) for Edge Defined Film-Fed Growth (EFG) silicon characterization. This OLCR sensor system has been used to measure horizontal profiles of silicon thickness and flatness to an accuracy of 1.5 Rim with the sensor head positioned 1 cm away from the silicon. The use of this noninvasive sensor for EFG silicon growth monitoring may lead to more efficient solar cell manufacturing processes.