| Solar cells,exploiting the photovoltaic effects,transform solar energy directly into electricity.Among them,thin-film solar cells have the advantages of low production cost,high power conversion efficiency and good device stability.What is more,they could be processed into flexible modules for a wide range of applications.Especially,solar cells based on CIGS and CdTe are intensively investigated.But,Due to the price issue of In and Ga and the toxity of Cd,we must seek novel solar cell materials with low-cost,non-toxity and high-efficiency materials.CuSbS2 and CuSbSe2 have sutiable bandgap and large absorption coefficients.Also,the elements of these two materials are all eco-friendly and inexpensive.This indicates that CuSbS2 and CuSbSe2 have the potential to be a successful absorber materials.In this thesis,the mateials properties and photovoltaic applicaitions of CuSbS2 and CuSbSe2 are thoroughly investigated.The following is the main content:(1)Using a hydrazine based solution process,single-phase Sb2(S,Se)3 films were successfully obtained.Through Raman spectroscopy,we have investigated the dissolution mechanism of Sb in hydrazine.Our study provides a valuable guidance for tuning the band gap in hydrazine solution processed Sb2(S,Se)3 alloy films for the future fabrication of improved photovoltaic devices.(2)Based on theoretical calculation and experimental investigation,the material properties(such as defect physics and photoelectric properties)related to photovoltaic application of CuSbS2 thin film were systematacially explored.Density functional theory calculations reveal that CuSbS2 has intrinsically p-type conductivity,which is determined by the dominant Cu vacancy(VCu)defects with a shallow ionization level and the lowest formation energy.Meanwhile,the formation energy and ionization level of other point defects were also studied.Using a hydrazine based solution process,phase-pure,highly crystalline CuSbS2 film with large grain size was successfully obtained.Also,the material and photoelectric properties were carefully investigated.Finally,we have built a prototype FTO/CuSbS2/CdS/ZnO/ZnO:Al/Au solar cell and achieved 0.50% solar conversion efficiency.(3)Using density functional theory calculations,CuSbSe2 is shown to have benign defect properties,i.e.,free of recombinationcenter defects,and flexible defect and carrier concentration.Next,systematic material,optical,and electrical characterizations uncover many unexplored fundamental properties of CuSbSe2.Finally,a prototype CuSbSe2-based thin film solar cell with an efficiency of 1.32% is fabricated by a hydrazine solution process,thus confirming the great potential of CuSbSe2 for thin-film solar cell applications.(4)Using a hydrazine based solution process,we have prepared a series of Cu-Sb-Se films by varying the annealing temperature from 100 to 520 °C.The dependence of phase composition,crystallographic orientation and electrical properties on annealing temperature were carefully studied.In particular,films prepared at 380 or 400 °C has the single-phase CuSb(Se0.96S0.04)2 with the tilted [013]-and [112]-oriented grains and low carrier concentration of ~1017 cm-3.Using this film as the absorber layer and CdS as the buffer,a photovoltaic device exhibiting 2.70% efficiency with a VOC of 0.27 V,JSC of 11.84 mA/cm2,FF of 40.51%(AM1.5G,100 mW/cm2)was obtained,showcasing the potential of CuSbSe2 for thin film solar cells. |
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