Arne Schmidt

Institute for Solar Energy Research (ISFH), Hamelín, Lower Saxony, Germany

Are you Arne Schmidt?

Claim your profile

Publications (5)8.41 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Increasing the area of interdigitated back-contact (IBC) solar cells featuring a busbar contact geometry requires the use of longer fingers. The finger resistance will, thus, be increased if the thickness of the metallization is kept constant. In order to maintain a thin metallization, it is beneficial to increase the num-ber of busbars per contact. However, using more than one busbar for each polarity implies an asymmetric contact geometry. As a consequence, under operation, the busbars of the same polarity carry different currents. Due to voltage drops over unavoidable electrical resistances, this may lead to significant potential differ-ences between these busbars. Since current–voltage characteristics are usually measured using separate sense contacts for the voltage measurement, the position and number of these contacts may con-siderably affect the shape of the resulting current–voltage charac-teristic and, thus, the fill factor. By means of simulations with the circuit simulator LTSpice, we show that a permanent contacting with soldered tabs allows for a correct determination of the fill fac-tor. A chuck used for temporary contacting should feature at least one sense contact per busbar and pin contacting resistances below 30 mΩ in order to keep the fill factor error below 0.5% absolute. Index Terms—Current–voltage characteristics, fill factor, inter-digitated back-contact (IBC) solar cell.
    IEEE Journal of Quantum Electronics 01/2012; 2(3):247. · 2.11 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We demonstrate industrially feasible large-area solar cells with passivated homogeneous emitter and rear achieving energy conversion efficiencies of up to 19.4% on 125 × 125 mm2 p-type 2–3 Ω cm boron-doped Czochralski silicon wafers. Front and rear metal contacts are fabricated by screen-printing of silver and aluminum paste and firing in a conventional belt furnace. We implement two different dielectric rear surface passivation stacks: (i) a thermally grown silicon dioxide/silicon nitride stack and (ii) an atomic-layer-deposited aluminum oxide/silicon nitride stack. The dielectrics at the rear result in a decreased surface recombination velocity of Srear = 70 cm/s and 80 cm/s, and an increased internal IR reflectance of up to 91% corresponding to an improved Jsc of up to 38.9 mA/cm2 and Voc of up to 664 mV. We observe an increase in cell efficiency of 0.8% absolute for the cells compared to 18.6% efficient reference solar cells featuring a full-area aluminum back surface field. To our knowledge, the energy conversion efficiency of 19.4% is the best value reported so far for large area screen-printed solar cells. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (RRL) - Rapid Research Letters 04/2011; 5(4). · 2.39 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report in detail on the luminescence imaging setup developed within the last years in our laboratory. In this setup, the luminescence emission of silicon solar cells or silicon wafers is analyzed quantitatively. Charge carriers are excited electrically (electroluminescence) using a power supply for carrier injection or optically (photoluminescence) using a laser as illumination source. The luminescence emission arising from the radiative recombination of the stimulated charge carriers is measured spatially resolved using a camera. We give details of the various components including cameras, optical filters for electro- and photo-luminescence, the semiconductor laser and the four-quadrant power supply. We compare a silicon charged-coupled device (CCD) camera with a back-illuminated silicon CCD camera comprising an electron multiplier gain and a complementary metal oxide semiconductor indium gallium arsenide camera. For the detection of the luminescence emission of silicon we analyze the dominant noise sources along with the signal-to-noise ratio of all three cameras at different operation conditions.
    The Review of scientific instruments 03/2011; 82(3):033706. · 1.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a fast and calibration-free carrier lifetime imaging technique based on photoluminescence (PL) measurements using an InGaAs camera for the examination of crystalline silicon wafers. The carrier lifetime is determined from the time dependent luminescence emission after optical excitation. A ratio, including four PL images acquired at different times during the modulated excitation, is calculated and found to depend only on the camera integration time and the effective carrier lifetime. Therefore, the carrier lifetime is unambiguously determined by this ratio without knowing any additional wafer parameter. We demonstrate the applicability of the dynamic PL technique to multicrystalline silicon wafers. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (RRL) - Rapid Research Letters 10/2010; 5(1):25 - 27. · 2.39 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report on calibration-free photoluminescence carrier lifetime imaging for the examination of crystalline silicon wafers. The photoluminescence measurements are performed using an indium gallium arsenide (InGaAs) camera. The carrier lifetime is determined from the time dependent luminescence emission for a modulated optical excitation. A ratio, including four photoluminescence images, acquired at different times during the modulated excitation, is calculated and found to depend only on the camera integration time and the effective carrier lifetime. Therefore, the carrier lifetime is unambiguously determined by this ratio without the knowledge of any additional wafer properties. The carrier lifetime is obtained locally by comparing the experimentally determined ratio with the simulated ratio for every image pixel. We demonstrate the applicability of the dynamic photoluminescence lifetime imaging technique to multicrystalline silicon wafers by comparison with microwave-detected photoconductance decay and quasi steady-state photoconductance decay measure-ments.
    Proc. 25th European Photovoltaic Solar Energy Conf., Valencia, Spain; 01/2010