| Solar energy is a kind of renewable energy known for its merits of clean and rich in resource.One of the hot research topics in this field is developing new materials and device structures to achieve low cost,high efficiency solar cells.In recent years,antimony chalcogenide,including Sb2S3、Sb2Se3,and Sb2(S,Se)3 are considered to be potential cadidates for its simple components,rich in resource and good stability.In this paper,we develop a co-evaporation method on antimony chalcogenide thin film deposition to regulate the thin film properties and improve the device efficiency.By employing such method,component,bandgap and interface of the device are studied and thus resulting in high photovoltaic conversion efficiency.The main content of the paper was conducted through the following five chapters:Chapter one,we briefly introduce the study background,working principle and classification of solar cells.The properties,synthesis methods and current status of antimony chalcogenide solar cells are then described in great detail.Finally,we put forward the research topics and major content included in this thesis.Chapter two,a co-evaporation method is applied into the research of Sb2S3 thin film deposition.By co-evaporation of Sb2S3 and S(Sb)powders,Sb2S3 thin films with different S/Sb ratio were achieved.We found S or Sb was dopoed into the lattice,thus formed S-rich or Sb-rich Sb2S3 film.Further research revealed that no obvious change on bandgap,morphology,and crystallinity of the films,however,devices fabricated by doped films have lower defect concentration.After systematically study the Sb2S3 component variation,thus its influence on devices efficiency,S-rich component act better performance and finally a champion device with 5.8%photovoltaic conversion efficiency is achieved.In this study,we develop a co-evaporation method in Sb2S3 thin film deposition which significantly improve the efficiency.Chapter three,we design a new equipment for antimony chalcogenide deposition which is based on its character.In this new equipment,a heating unit of substrate with over 500℃ and variable distance from 10 to 30 cm between the source and substrate are realized.After regulation,a substrate temperature of 315℃ and a source-to-substrate distance of 10 cm was defined as best deposition condition.In the subsequent study,we deposite Sb2(S,Se)3 films by co-evaporating Sb2Se3 and S powder and find that varing the timing of S evaporation will not only change the bandgap but the crystallographic orientation of the films.Finally,the best device were obtained when the evaporation of S was 45 s after Sb2Se3 starts evaporating which avoided the generation of defects at the CdS/Sb2(S,Se)3 interface as well as achieved a uniform Sb2(S,S e)3 thin film.This study revealed the growth mechanism of Sb2(S,Se)3 thin film and provided a method to fabricated high efficiency Sb2(S,Se)3 solar cells with 8.0%.Chapter four,a bandgap engineering method was introduced to promote the Voc of solar cells.An ultra-thin film of Sb2S3 was deposited on the Sb2(S,Se)3 thin film,thus formed a back surface gradient(BSG)bandgap(small bandgap at the front surface and large bandgap at the back surface).The deposition of Sb2S3 grows along the Sb2(S,Se)3 thin film,filled the pine hole on Sb2(S,Se)3 surface and enhanced the build-in potential.As a result,the Voc of Sb2(S,Se)3 solar cell increased from 0.46 to 0.5 V,and the efficiency increased from 4.9%to 6.4%.This study illustrated a simple BSG bandgap method increasing the Voc of Sb2(S,Se)3 solar cell as well as lays a foundation for the subsequent preparation of V-shaped bandgap films.Chapter five,the research of this paper was summarized,thus advices were proposed to look forward the development direction of antimony chalcogenide. |
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