Darmstadt 2008 – wissenschaftliches Programm

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SYLM: Symposium Lasermaterialbearbeitung

SYLM 2: Funktionalisieren

SYLM 2.3: Hauptvortrag

Mittwoch, 12. März 2008, 17:30–18:00, 2B/C

Laser processing for highly efficient crystalline Si solar cells — •Rolf Brendel, Sonja Hermann, and Thobias Neubert — Institut für Solarenergieforschung Hameln (ISFH), Germany

In order to enhance the solar absorption of Si solar cells it is advantageous to structure the surface as to enhance light trapping. Some of the widely used Si materials can hardly be textured by wet chemical etching. In this case structuring a dielectric layer with an excimer laser and subsequent chemical etching is an attractive alternative. Solar absorption is also enhanced by placing both contacts on the back side of the cell since this reduces the front side shadowing. However, a low-cost patterning step is then required on the contacted side. Direct patterning of Si with ns-pulses laser pulses may be used as an alternative to photolithography. In order to have as few as possible electron-hole pairs recombine with each other, both cell surfaces have to be electronically passivated by silicon dioxide or silicon nitride. For contacting the cell, these dielectric layers have to have local openings. We find the direct ablation of silicon dioxide with ps-laser pulses to be a low-damage rout to form contact openings. This presentation quantifies the recombination losses in laser-processed back-contacted Si solar cells. We pay particular attention to the processing speed that is achievable with todays laser technology and to the recombination losses introduced by laser processing. We report on power conversion efficiencies up to 21.4% that we achieve on an aperture area of 92 cm^2.