Preparation And Photovoltaic Characteristics Of Thermally Evaporated Sb₂Se₃ Thin Film Solar Cells

Energy shortage has always been a worldwide problem.The total amount of traditional energy is limited and serious environmental pollution.It is urgent to seek new alternative energy.Solar energy has high research value because of its green,clean,pollution-free and inexhaustible advantages.the Sb₂Se₃ material has excellent optical properties,environmentally friendly,non-toxic,and abundant reserves.It is a promising new type of inorganic thin-film solar cell absorber material.In recent years,its highest device conversion efficiency has also continuously achieved breakthroughs,reaching the highest 9.2%,but the theoretical efficiency of 23%is still far behind,and the problem that restricts the conversion efficiency of the device has not been completely solved.Therefore,it is necessary to conduct more in-depth research on Sb₂Se₃ thin-film solar cells.The thermal evaporation method is a very convenient and high-quality preparation method.It is widely used in the field of solar cells.Compared with other preparation methods,it has better adaptability in large-area areas.However,it is used in antimony selenide thin-film batteries.There are still various problems such as poor film quality and low open circuit voltage.Therefore,this study chose thermal evaporation to prepare antimony selenide thin films.By controlling the preparation process and annealing atmosphere,the annealing mechanism under H2S atmosphere was studied.At the same time,based on the previous research,the mechanism of using spray pyrolysis to prepare a pyrolyzed tungstate layer as a hole transport layer to improve the conversion efficiency of the device is explored.details as follows:In order to study the growth mechanism and carrier transport process of Sb₂Se₃ thin films,this subject used an improved rapid thermal evaporation equipment to prepare Sb₂Se₃ thin films,and adjusted the cooling rate,thermal evaporation time,thermal evaporation temperature,substrate rotation rate,etc.In all aspects,the quality of the Sb₂Se₃ film is improved.On the basis of the above experimental results,by adding post-treatment annealing process to the Sb₂Se₃ film,the film can be further improved and improved.Through annealing in various atmospheres(N₂,Se,S,H₂S)and combining different annealing temperature,annealing time and other variables,the improvement of device conversion efficiency directly reflects the improvement of film quality.In addition,in-depth analysis The carrier transport mechanism,energy band change mechanism,and defect vacancy formation mechanism of Sb₂Se₃ film during the annealing process are explained.The reason for the better quality of the film annealed under H₂S atmosphere is explained,and its superiority compared with other atmospheres is proved.When annealed in an H₂S atmosphere,a very thin Sb₂S₃ layer is formed on the surface,and the internal Se atoms are partially replaced by S,and S and Se atoms will diffuse in a small range in the Sb₂S₃ layer with a diffusion length of about 10 nm.In the thermal evaporation process,a small part of Se sublimates and there are Se vacancies,forming a deep energy level in the band gap.When S diffuses into the inside of the film,the formation of vacancy defects is prevented,so the charge recombination phenomenon inside the film is reduced.The lifetime of the currents is increased,thereby improving the conversion efficiency of the device.And from the perspective of energy level,it can be analyzed that although the existence of the Sb₂S₃ layer will create a potential barrier,making it more difficult for the charge to transfer to the surface,but at the same time,due to the existence of the potential barrier,the open circuit voltage can be slightly increased,and because The thickness of the Sb₂S₃ layer is very thin,and the impact on the energy level mismatch is minimized.In addition,100 different devices were prepared,and the performance difference between the devices was small,which proved that their stability was also very outstanding,and the final conversion efficiency of the devices reached 6.2%.Using the spray pyrolysis method,a layer of amorphous pyrolytic tungstate film is sprayed on the Sb₂Se₃ film,and by adjusting different spraying cycles and deposition temperatures,it can be better deposited on the surface of the Sb₂Se₃ film.The layered pyrolyzed tungstate film can increase hole collection and reduce back contact resistance,thereby reducing carrier recombination,improving carrier collection,and improving J_SC.In addition,the pyrolytic tungstate forms a layer at the grain boundary,which passivates the harmful defects on the back side and reduces the recombination loss on the back side,and reduces the leakage channel at the grain boundary.Finally,a device conversion efficiency of 3.78%was achieved.It proves that the hole transport layer has potential application value for improving Sb₂Se₃ solar cells.All in all,the improved thermal evaporation equipment has certain advantages.Annealing under H₂S atmosphere will react with the surface oxide layer to form an Sb₂S₃ layer,reduce surface defects,and improve device conversion efficiency.The sprayed pyrolyzed tungstate layer improves the conversion efficiency of the device by reducing the leakage channels on the back side and improving the hole collection efficiency.