Of Fes <sub> 2 </ Sub> Thin Film Of The Organizational Structure And Optical And Electrical Properties

FeS₂ (pyrite) has been considered as a valuable semiconductor for solar energy conversion and other photoelectrochemical applications since it consists of nontoxic and abundant elements. Because of the band gap of about 0.95eV and the very high light absorption coefficient (λ<700nm时,α>5×10⁵cm^-1), it might be suitable for sensitization solar cells and in the form of ultrathin films.The effects of the sulfidation parameters on the microstructure and photoelectrical characteristics of FeS₂ thin films have been investigated by the sulfidation annealing for the Fe films under different temperature, time and pressure. The results indicate that the reaction temperature to form FeS₂ fully is 400 癈. Higher temperature than 400癈 makes an insignificant acceleration to the conversion from Fe to FeS2. Higher sulfidation temperatures can results in coarser FeS2 grains, higher electrical resistivity and higher possibility to produce p-type thin films. The crystal grains propagate with prolonging the annealing time. With the prolongation of the annealing time at 400 "C and SOkPa, the energy gap and the electrical resistivity increase and all the thin films trend to n-type semiconductors. The influence of sulfidation pressure on microstructure is insignificant. The electrical resistivity is lower because the carrier concentration is very higher for the films annealed at lOOkPa sulfidation pressure.Fe layers of different thickness have been converted to FeS2 thin films by thermal sulfidation. The influence of the thickness on the crystal structure, electrical resistivity, carrier concentration, absorption coefficient and energy gap of FeS2 thin films have been investigated. The results indicate that with increasing the thickness of FeS2 thin films, the electrical conductivity, the carrier concentration and the absorption coefficient decrease. Moreover, the energy gap increasing with the film thickness when that is in the range of 70-130nm while the energy gap decreases with the film thickness when that is above 130nm.The samples of sensitization solar cell have been produced by using FeS2/Ti02 as an electrode for studying the photoelectrical conversion efficiencies of FeS2 thin films. The photoelectrical conversion efficiencies of the samples have been measured and the influence of the thickness of film on photoelectrical conversion efficiency has beeninvestigated. The results indicate that the photoelectrical conversion efficiency firstly decreases and then increases with increasing the thickness of the films. The photoelectrical conversion efficiencies of all films are generally at a rather low level. The influence of pH value of electrolyte on open circuit photovoltage and short circuit photocurrent is very significant.