Structural, electrical and photovoltaic characterization of Si

摘要

Thin films of Si nanocrystals (Si NCs) embedded in a silicon carbide (SiC) matrix (Si-NC:SiC) were prepared by alternating deposition of Si-rich silicon carbide (Si1-xCx) and near-stoichiometric SiC mutilayers (Si1-xCx/SiC) using magnetron cosputtering followed by a post-deposition anneal. Transmission electron microscopy and Raman spectroscopy revealed that the Si NCs were clearly established, with sizes in the range of 3-5 nm. Optical studies showed an increase in the optical band gap after annealing from similar to 1.4 eV (as-deposited) to similar to 2.0 eV (annealed at 1100 degrees C). P-type Si-NC:SiC/n-type crystalline silicon (c-Si) heterojunction (HJ) devices were fabricated and their electrical and photovoltaic properties were characterized. The diode showed a good rectification ratio of 1.0 x 10(4) at the bias voltage of + 1.0 V at 298 K. The diode ideality factor and junction built-in potential deduced from current-voltage and capacitance-voltage plots are similar to 1.24 and 0.72 V, respectively. Illuminated I-V properties showed that the I-sun open-circuit voltage, short-circuit current density and fill factor of a typical HJ solar cell were 463 mV, 19mA/cm(2) and 53, respectively. The external quantum efficiency and internal quantum efficiency showed a higher blue response than that of a conventional c-Si homojunction solar cell. Factors limiting the cell's performance are discussed. (c) 2007 Elsevier B.V. All rights reserved.