The investigation of different selective emitter (SE) approaches [1-3] is a current trend in solar cell manufacturing. The incorporation of a local high phosphorous doping underneath the front contact grid allows for the use of high-sheet resistance illuminated emitters that combine low recombination and improved blue response. Further efficiency increase compared to the standard screen-printed solar cell is achieved via plated contacts [4-5] that feature better aspect ratio and optical properties [6], higher line conductivity and smaller width [5] compared to screen-printed contacts. In this paper we present detailed technological requirements for next-generation front side metallization as well as experimental results of the RENA high-efficiency metallization cluster consisting of Laser Chemical Processing (LCP) and Ni-Ag light-induced plating (LIP). It becomes clear that efficiency on cell level is not the only figure of merit for a successful product and that the co mbination of SE with plating has a much higher potential for increasing cell efficiency than the metallization of SE via screen-printing

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We report on the generation of tunable, ultrashort THz radiation between 2.0 and 5.3 THz by optical rectification of femtosecond laser pulse trains in the highly nonlinear crystal 4-dimethylamino-N-methyl-4-stilbazolium tosylate ( DAST) . Femtosecond pulse trains with a THz repetition rate are successfully synthesized from a single laser pulse using a zone plate which consists of a stack of thin glass plates. Using four glass slides we could experimentally demonstrate a substantial narrowing of the spectral bandwidth of the THz radiation. The spectral characterization of the THz pulses is accomplished using a Michelson interferometer. By simply tilting the zone plate the peak frequency is tuned from 2.0 to 5.3 THz. Even though higher and lower frequencies can be generated, the reported range is limited by the spectral characteristics of our detector. To our knowledge, our work demonstrates the first application of a zone plate for the generation of ultrashort THz pulses, tunable over a very large spectral range.