Antireflection coatings for silicon solar cells have been optimized both theoretically and experimentally for a range of possible situations, such as single-layer and double-layer coatings, and on planar and microgrooved surfaces. The effect of a thin passivating silicon dioxide layer under the coating was also considered. A critical passivating oxide thickness of about 300 AA was found to be important for the design of these coatings. A new half-quarter-wavelength double layer antireflection coating can be achieved with very low reflection if the passivating oxide has to be thicker than this critical thickness. >

Optimized antireflection coatings for high-efficiency silicon solar cells

Computer simulation of the effects of electrical mismatches in photovoltaic cell interconnection circuits

Numerical simulation of current-voltage characteristics of photovoltaic systems with shaded solar cells

In 2006, around 86% of all wafer-based silicon solar cells were produced using screen printing to form the silver front and aluminium rear contacts and chemical vapour deposition to grow silicon nitride as the antireflection coating onto the front surface. This paper reviews this dominant solar cell technology looking into state-of-the-art equipment and corresponding processes for each process step. The main efficiency losses of this type of solar cell are analyzed to demonstrate the future efficiency potential of this technology. In research and development, more various advanced solar cell concepts have demonstrated higher efficiencies. The question which arises is “why are new solar cell concepts not transferred into industrial production more frequently?”. We look into the requirements a new solar cell technology has to fulfill to have an advantage over the current approach. Finally, we give an overview of high-efficiency concepts which have already been transferred into industrial production.

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Industrial Silicon Wafer Solar Cells

The surface recombination velocity s for silicon surfaces passivated with thermal oxide was experimentally determined as a function of surface phosphorus concentration for a variety of oxidation, anneal, and surface conditions. This was accomplished by measuring the emitter saturation current density J/sub 0/ of transparent diffusions for which the J/sub 0/ is strongly dependent on s. At the lowest doping levels, the value of s was confirmed by measurements of s on substrates with uniform phosphorus doping. The impact of these measurements on solar cell design is discussed. >

Studies of diffused phosphorus emitters: saturation current, surface recombination velocity, and quantum efficiency

Abstract The passivated emitter solar cell (PESC) structure has been responsible for recent improvements in silicon solar cell performance. The effect of substrate resistivity upon PESC cell performance is described. Also described is the performance of cells on both 0.5 ω cm Czochralski and float zone substrates. Finally recent results are described which have resulted in 19.8% energy conversion efficiencies measured relative to NASA calibrated reference cells.

Improvements in silicon solar cell efficiency

A combination comprises a device for receiving and for directing incoming light in a three dimensional manner to at least one predetermined location together with a solar cell. The device has two light reflecting surfaces and a total internal reflection surface. In operation, the total internal reflection surface transmits the incoming light into the device and totally internally reflects the light reflected from the surface which is incident at its surface at an angle within the range for total internal reflection. The reflection surfaces are operatively disposed with respect to one another so as to perform the function of a receiver/director by directing incoming light in a three dimensional manner to the rear surface of the solar cell.

Optical design for photo-cell

Without appropriate protection, partial shading of solar cell modules can have two undesirable effects. In the best case, partial shading can disproportionately reduce module output. In other cases, such shading can cause local overheating of the module and cause module destruction. This paper describes a simple technique which eliminates both problems. A bypass diode is integrated into the cell structure during cell processing with only one extra processing step required in representative processing sequences. The small associated cost is likely to be more than offset by increased module reliability, greater output in the field due to improved shadow tolerance, and simpler module assembly compared to discrete bypass diode approaches. The paper describes the underlying concepts, experience with producing such cells in pilot production quantities and the performance of solar cell modules and arrays incorporating these cells.

S. R. Wenham

Papers

Improvements in silicon solar cell efficiency

Optical design for photo-cell

Silicon solar cells with integral bypass diodes

Recent advances in high efficiency silicon solar cells

Improvements in flat-plate and concentrator silicon cell efficiency