Study Of Optical And Electrical Properties Of Pyrite

FeS2 which is cubic has an appropriate forbidden band width (Eg=0.95 eV) and higher light absorption coefficient (whenλ<750nm,α>6×105cm-1),its constituent elements reserves abundant, non-toxic, good environmental compatibility, it is a extremely potential solar battery material. However, although the theoretical calculation shows that the photoelectric conversion efficiency of FeS2 can achieve 15% to 20%, but photoelectric conversion efficiency of the present laboratory FeS2 solar battery can only achieve 2.8%, that has vary considerably with the theoretical. The low efficiency of photoelectric transformation greatly limits the practical application of FeS2, and the electro-optical property of FeS2 is the main factor which effect the photoelectric conversion efficiency. Therefore, the study of electro-optical property of FeS2 can not only reflect the rationalization of FeS2 preparation technology, but also have great significance to improve the photoelectric conversion efficiency of FeS2 solar battery and promote its future application of photoelectric devices.Natural conditions and basic process of pyrite formation were simulated in this paper, we had prepared the FeS2 powder by the thermal curing method under the different temperature condition (593 K,613 K,633 K,653 K,673 K,693 K). we used the X' Pert Pro which is polycrystalline X-ray diffraction instrument (XRD) to analyze the crystal structure of FeS2 powder,According to the half width of diffraction peak height from XRD patterns we estimated grain size of powder samples by the scherrer formula, Used SSX-550 which is field emission scanning electron microscopy (SEM) to observe the morphology of the FeS2 powder, The results showed that the grain size of samples are in the nm order of magnitude, and with the curing temperature rising, curing reaction become more fully, the grain size has an increasing trend; Measured absorbance of the samples with UV-Vis-NIR Spectrophotometer, calculated the absorption coefficient, and got the forbidden band with the Tauc Rules. This paper mainly analyzed the impact of the vulcanization temperature over FeS2 optical quality, the results showed that:The vulcanization temperature affected the samples'optical properties by changing crystalline state, grain size and defect concentration; since quantum size effect, the measured absorption edge we occurred the blue shift and the forbidden band become more wider; And by the curing temperature increasing within 593 K-653K range, the grains became larger and S/Fe value raised, so that the quantum size effect become weaker, forbidden band width was diminished; The forbidden band width of FeS2 made at the 635K vulcanization temperature was about 1.4 eV theoretically corresponding the highest photo-electricity conversion efficiency; using with a hydraulic machine Powder samples pressed into discs, using HL5500 Hall test system we measured the resistivityρ,Hall coefficient RH,carrier concentration N and carrier mobilityμ, of the samples obtained under different experimental conditions at room temperature. Focus on Analysis of the effect of curing temperature on the optical properties of FeS2,we found:in the range of 613K-693K, with curing temperature rising, the grain size increases, and the S/Fe values increase in the overall trend, so that the carrier concentration decreased with increasing temperature, while the migration rate rises, the trend of resistivity of the FeS2 sample made under the conditions of curing from 613K to 653K temperature mainly dominant by carrier mobility, and in the 653K-693K the trend of the resistivity dominant by the carrier.