PHOTOVOLTAIC OUTPUT LIMITATION OF N-FES2 (PYRITE) SCHOTTKY BARRIERS - A TEMPERATURE-DEPENDENT CHARACTERIZATION

Metal/n-pyrite (metal = Pt, Au, Nb) Schottky barrier type diodes were fabricated on electrochemically reduced either synthetic or natural (100) and (111) surfaces of single crystalline n-FeS2. The temperature dependence of I - V curves in darkness were analyzed in the range of 200-350 K on the basis of thermionic emission and recombination models. The calculated effective barrier height was approximately 0.60 eV and the activation energy for recombination approximately 0.50 eV for all investigated n-FeS2/Pt samples. The doping density and the extrapolated potential (pseudo flatband situation) from the Mott-Schottky plot, obtained from capacities deduced from potentiostatic complex impedance measurements, were 2.0 x 10(16) cm-3 and 0.25 eV vs Pt for the synthetic n-pyrite crystal, respectively. From the donor density and barrier height a band bending of 0.5 eV was deduced. Photovoltaic parameters like open-circuit photovoltage and short-circuit photocurrent were studied down to temperatures of 200 K. The main phenomenon preventing the generation of a photopotential approaching the band bending (0.50 eV) appears to be the pinning of the Fermi-level by recombination centers located in the middle of the band gap (E(g) = 0.95 eV) of pyrite.