Investigation Of Doping In Antimony Selenide (Sulfide) Thin Film And Its Application In Solar Cells

Nowadays,the overuse of fossilfuels makes energy scarce and brings about serious environmental pollution with the development of modern industrialization.It is urgent to explore renewable energy.The usage of clean and green renewable solar energy is an effective way to realize the harmonious and sustainable development between human beings and nature by converting solar energy into electricity through the photovoltaic effect.The first generation PV devices,represented by C-Si solar cells,have developed very well and been appiled in large-scale industrial production.The 2nd generation of PV,represented by cadmium telluride(CdTe),gallium arsenide(GaAs),copper indium gallium selenium(GIGS),etc.are developing and only take a tiny percentage in current PV market.The toxic,scarcer properties of some components limit their further development.Researchers have never stopped exploring new PV materials and new solar cell structures to meet the requirement of the development of human societyAntimony selenide(Sb2Se3)and antimony sulfide(Sb2S2),as one-dimensional inorganic compound materials,have high absorption coefficient,environmental friendly.They have received more and more attention recently,due to the good carrier transport characteristics and suitable optical band gaps,this thesis focus on the improvement of electrical properties of selenium(sulfur)antimony chalcogenide films by doping and modification.The works can be divided into three partsFirst,fullerene(C60)was introduced into the Sb2S3 thin films to improve the electrical conductivity.The inteoduction of C60 effectively improved the film conductivity,and it would be helpful to the transport and collection of photo-generated carriers in the Sb2S3 thin film solar cells,while the crystallinity and optical properties were kept nearly the same with the un-modified Sb2S3 thin films.We fabricated superstrate configuration of SnO2:F(FTO)/TiO2/Sb2S3(C60)/Spiro:OMeTAD/Au planar heterojunction solar cells,and it showed better short-circuit current,fill factor,and conversion efficiency than devices without C60 modification in the absorption layer.This work provides a new research view for the improvement of Sb2S3 conductivity and also improving device efficiency.Secondly,implement the possibility to controllably vary the carrier density of Sb2Se3-based absorbers in the range form 1016-1019 cm-3 by incorporating Ag into the Sb2Se3 absorbers,which leads to the formation of a(Sb2Se3)R(AgSbSe2)1-x alloy.The close spaced sublimation(CSS)process was used to deposit the(Sb2Se3)x(AgSbSe2)1-x alloy film.The Ag distribution is dependent on the substrate temperature.The carrier density for the optimized(Sb2Se3)x(AgSbSe2)1-x alloy is about three order of magnitude higher than that for pure Sb2Se3 films(1013-1014 cm-3).Eventually,we fabricated the Sb2Se3-based thin film solar cells in the substrate configuration of Au/AZO/i-ZnO/CdS/(Sb2Se3)x(AgSbSe2)1-x/MoSe2/Mo,and it showed better open circuit voltage(VOC)and conversion efficiency than reference cell with a pure Sb2Se3 absorber.This higher carrier density allows the device VOC to reach an initial value of 475 mV and increase to 508 mV after more than 1100 hours illumination.As a consequence,a noticeable improvement in VOC by>18%is observed in solar cells based on(Sb2Se3)x(AgSbSe2)1-x alloy absorber layer,as compared to the reference cell with a pure Sb2Se3 absorber,leading to a high conversion efficiency of 7.8%.This work offers a new research direction for solving the low intrinsic carrier density and high VOC deficit issues in Sb2Se3-based solar cells.Finally,the ternary absorption layer of selenium antimony sulfide was studied.We implement the possibility to controllably vary the band gap of Sb2(Se1-xSx)3 absorbers.The close spaced sublimation(CSS)process was used to deposit the(Sb2Se3)x(AgSbSe2)-1x alloy film.Eventually,we fabricated the thin film solar cells in the substrate configuration of Au/AZO/i-ZnO/CdS/(Sb2Se3)x(AgSbSe2)1-x/MoSe2/Mo.As a consequence,the band gap of the synthesized Sb2(Se0.51S0.49)3 film is 1.42eV,when the ratio of Sb2Se3 to Sb2S3 is 2:1.This suitable band gap allows the device VOC to reach an initial value of 520 mV,leading to a high conversion efficiency of 8.57%.This work offers a new research direction for obtaining a series of sing-phase Sb2(Se1-xSx)3 sources and getting low-cost,high-efficiency Sb2Se3-based solar cells.The electrical properties are the key factors affecting the solar cell performance.This thesis explores some measurements to analyze the impact of doping and modification on the physical properties of Sb2Se3 or Sb2S3.More works are required to improve the film surface,junction interface,band structures in the hetrojunction solar cells to obtain higher solar cell efficiency.