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One main efficiency loss in industrial solar cells is the shading of the cell caused by the metal front side contacts. With the aerosol-printing technique plus an additional light-induced plating (LIP) step, not only is the geometrical contact width narrowed compared to screen-printed contacts but also the shape of the finger changes. In this work, the effective shading of different finger types is analysed with two different measurement methods. The essential parameter for characterising the finger is the effective width which can be reduced drastically compared to the geometrical width due to total internal reflection at the glass-air layer and the reflection from the roundish edges of the contact fingers into the cell. This parameter was determined with different methods. It could be shown that for aerosol-printed fingers the effective (optical) width is only 38% of its geometrical width, while for standard screen-printed fingers it is 47%. The measured values are compared to a theoretical model for an aerosol-printed and plated finger and are in good agreement. [ABSTRACT FROM AUTHOR]

A novel plasma-enhanced chemical vapour deposited (PECVD) stack layer system consisting of a-SiOx:H, a-SiNx:H, and a-SiOx:H is presented for silicon solar cell rear side passivation. Surface recombination velocities below 60 cm/s (after firing) and below 30 cm/s (after forming gas anneal) were achieved. Solar cell precursors without front and rear metallisation showed implied open-circuit voltages Voc values extracted fromquasi-steady-state photoconductance (QSSPC) measurements above 680mV. Fully finished solar cells with up to 20.0% energy conversion efficiency are presented. A fit of the cell's internal quantum efficiency using software tool PC1D and a comparison to a full-area aluminium-back surface field (Al-BSF) and thermal SiO2 is shown. PECVDONO was found to be clearly superior to Al-BSF. A separation of recombination at the metallised and the passivated area at the solar cell's rear is presented using the equations of Fischer and Kray. Nuclear reaction analysis (NRA) has been used to evaluate the hydrogen depth profile of the passivation layer system at different stages. [ABSTRACT FROM AUTHOR]

Discusses future solar cells, which are believed will be thinner, of higher efficiency and produced in greater numbers. How passivated emitters and rear cells are solar cell concepts able to fit these developments; View that with a new laser-based process (laser-fired contacts), the rear point contact pattern of this concept can be implemented industrially; Data suggesting the high potential of the new laser-based technique.

Thin solar cells on industrial Czochralski-material were produced and analyzed. For the Random Pyramid - Passivated Emitter and Rear Cell(RP - PERC) with planar rear surface, a maximum efficiency of near 20% was achieved for 115 as well as 165 m thickness. In comparison, cells textured at the rear surface with a standard industrial process reached about a 2% (absolute) lower efficiency. This difference is consistently explained by an increased rear surface recombination, whereas light trapping properties are excellent for both rear surface treatments. The Cz-specific light-induced degradation of the thin cells is investigated. [ABSTRACT FROM AUTHOR]

A set of p-type Czochralski (Cz) silicon materials grown by Shin-Etsu Handotai was used for a comprehensive investigation, including carrier lifetime measurements and fabrication of high-efficiency solar cells at Fraunhofer ISE. The set of different materials consists of gallium and boron doped wafers grown with the Cz method and boron doped wafers grown with the magnetic Czochralski (MCz) method. A clear correlation of the Cz-specific lifetime degradation and the concentrationof boron and interstitial oxygen was observed. Thus, gallium-doped wafers with a high concentration of interstitial oxygen of 1377 ppm showed no degradation. Excellent stable lifetimes of 1098 mu s and 862 mu s were determined for boron-doped MCz wafers and for gallium-dopedCz wafers, respectively. This high lifetime level was maintained or even improved throughout the cell process optimized for Cz silicon and record efficiencies of 2277% and 2275% were achieved for boron-doped MCz silicon and gallium-doped Cz silicon, respectively. [ABSTRACT FROM AUTHOR]