Controllable-orientations For Wide Bandgap Sb2S3 Thin Film Deposition And Photovoltaic Device Application

In recent years,the energy problem has promoted the rapid development of the photovoltaic industry.As the core device for achieving photoelectric conversion,solar cel s have been extensively studied.Silicon-based cel s are currently the most successful commercial cel s,but conversion efficiency is approaching theoretical limits.The band gap of silicon is about 1.1 eV.Finding a wide bandgap material(1.7 eV-1.8 eV)to fabricate a silicon-based tandem solar cell is an effective way to break the efficiency limit of crystal ine silicon cel s.As a new type of optoelectronic material,antimony sulfide has a band gap of about 1.7 eV,high light absorption coefficient,simple structure and abundant reserves.The use of antimony sulfide cell as"wide bandgap blue-light top cel"for silicon tandem solar cell can further improve the performance and has breakthrough application potential.So our research focuses on wide bandgap Sb₂S₃ film deposition and solar cell device,including the following aspects:Sb₂S₃ film deposition with controllable orientations and growth mechanism study.1)Sb₂S₃ has a unique quasi-one-dimensional structure and strong anisotropy.Therefore,the orientation of the film has a great impact on the device performance.Here a new vertical vapor deposition method(V-VTD)was designed and realized.For the first time,the orientation of Sb₂S₃ films could be controlled.By using different temperature windows,high quality Sb₂S₃film with[hk0]orientation or[hk1]orientation could be accurately obtained.Unlike traditional methods,the orientation of the absorption layer prepared by V-VTD had no substrate dependence.2)The orientation convert of Sb₂S₃at different deposition time and temperature were systematical y analyzed.The orientation information of Sb₂S₃ film at different depths were obtained by using solution to etch film layer by layer.The above results showed that the synergistic effect of the film deposition rate and re-evaporation rate affected the film growth process and final orientation.Based on this,a possibleV-VTD antimony sulfide crystal growth model was proposed,which showed the growth and film formation process of Sb₂S₃ at different temperatures and times.The corresponding growth model could fit the experimental data well.Preparation of CdS/Sb₂S₃ heterojunction device based on V-VTD.Being able to work normally as a single cell is a prerequisite for application in tandem solar cel s.Therefore,in this thesis,a device with Glass/ITO/CdS/Sb₂S₃/Au structure was assembled.After system analysis and comparison,the solar cel s with[hk1]preferred orientation showed higher conversion efficiency,fewer interface defects,larger built-in electric field and higher external quantum efficiency(EQE).Further,the post-selenization process developed for the RTE system had been optimized.A confined space selenization method was applied to obtain a higher selenium atmosphere without damaging the Sb₂S₃ film and improve the back contact of the superstrate device.The final efficiency reached 4.5%,theV_OC of 730 mV was the top value among the Sb₂S₃ solar cel s fabricated by vacuum method.By depositing Sb₂S₃film on Mo/Mo Se₂ layer via V-VTD,CdS/Sb₂S₃heterojunction device with substrate structure was fabricated.The device showed 1.5%efficiency.Preparation of TiO₂/Sb₂S₃ heterojunction device based on V-VTD.Because CdS had absorption in the short-wave and contained toxic Cd elements,TiO₂film prepared by spray pyrolysis,ALD and hydrothermal methods were used to replace CdS as buffer layer.Because of the unevenness of the spray TiO₂,the devices showed lower performance.On the contrary,the film deposited on ALD TiO₂showed good crystal inity and excel ent(221)orientation.The PCE achieved 3.05%when applied to planar junction Sb₂S₃ cell for the first time.Then by optimizing the hydrothermal process,TiO₂ nanowires with diameters in the tens of nanometers were converted into 10?m diameter TiO₂ film composed by nanocrystalline bulk array.Its array structure could increase the parallel resistance of the device,and suppress the leakage current of the device.