J. Steinhauser

Transition between grain boundary and intragrain scattering transport mechanisms in boron-doped zinc oxide thin films

A comprehensive model for the electronic transport in polycrystalline ZnO:B thin films grown by low pressure chemical vapor deposition is presented. The optical mobilities and carrier concentration calculated from reflectance spectra using the Drude model were compared with the data obtained by Hall measurements. By analyzing the results for samples with large variation of grain size and doping level, the respective influences on the transport of potential barriers at grain boundaries and intragrain scattering could be separated unambiguously. A continuous transition from grain boundary scattering to intragrain scattering is observed for doping level increasing from 3×1019to2×1020cm−3.

Micromorph Solar Cell Optimization using a ZnO Layer as Intermediate Reflector

The insertion of a zinc oxide (ZnO) intermediate reflector (ZIR) between the top and bottom cell of a superstrate (p-i-n/p-i-n) micromorph tandem solar cell is analyzed, experimentally and by numerical simulation. Solar cells are deposited onto glass plates coated by surface-textured ZnO layers deposited by low-pressure chemical vapour deposition (LP-CVD). The gain in the top cell short-circuit current density (Jsc) obtained by ZIR insertion as well as the corresponding loss for the bottom cell are experimentally observed, for different values of ZIR thickness d. The gain and the loss depend nearly linearly on ZIR thickness for d < 100 nm, the maximum gain is almost 3 mA/cm2. Experimental results are compared with an optical simulation. In the latter a three-layer effective media approximation is used for modeling of thin ZIR layers. Micromorph tandem solar cells were deposited on 2 different types of front LP-CVD ZnO layers: (a) a layer optimized for a-Si:H single-junction solar cells; (b) ZnO layers specially developed for muc-Si:H cells and having undergone a novel surface treatment. In case (a) Jsc=12.1 mA/cm2 and initial conversion efficiency is 11.6 %; in case (b) Jsc=12.8 mA/cm2 and initial conversion efficiency is 11.8 %. The open-circuit voltage (Voc) value could be improved from 1.32 V to 1.41 V with an increased surface treatment time

Boron Doping Effects on the Electro-optical Properties of Zinc Oxide Thin Films Deposited by Low-Pressure Chemical Vapor Deposition Process

Note: IMT-NE Number: 453 Reference PV-LAB-CONF-2006-013 Record created on 2009-02-10, modified on 2017-05-10