Research On Fabrication And Photovoltaic Properties Of SnO₂ Based Perovskite Solar Cells

Renewable energy such as solar energy,plays a vital role in achieving sustainable development,and solar cells are efficient ways of utilizing solar energy.Recently,the solar cells based on hybrid perovskite materials have been shown a rapid development,with a certified photo-to-electron conversion efficiency achieved 22.7%in 2017 through the tireless efforts of the researchers.In perovskite based solar cell structure,the quality of the electron transport layer plays a very important role in the performance of perovskite solar cells which efficient transport electrons and blocking the holes,respectively.Reducing the preparation temperature of the electron transport layer can simplify the process and cost of battery preparation,and it is of great significance for the future industrial production in large areas.In this paper,the study focuses on low temperature possible of high quality tin oxide electronic transport materials based perovskite solar cell,the main contents in the study as follows:In this chapter,the mesoporous structure is applied to perovskite solar cells,and different thickness?40nm,70nm and 90nm?tin oxide compact layer were kept by spin-coating times to study the effect on the Photovoltaic properties of perovskite solar cell based on MAPbI3 active layer.The SnO₂ films were characterized by X-ray diffraction?XRD?and X-ray photoelectron spectroscopy?XPS?,which showed this low temperature processed film was amorphous SnO₂.The microstructure and transmittance of the substrate were characterized by scanning electron microscopy?SEM?and ultraviolet visible spectrophotometer?UV-Vis?,results showed that the coverage of the substrate increased with the increase of the thickness of the SnO₂ film,and the transmission of the film wad increased firstly and then decreased.Finally,the best photovoltaic conversion efficiency?average 10.84%,up to 12.23%?based on 70nm thick SnO₂ compact layer is obtained,and dynamic process in the cell is analyzed by electrochemical impedance spectroscopy?EIS?,shows that the largest recombination resistance at 70nm SnO₂ based device,which is consistent with the test results.A 30 minute SnCl₄ modification was used to improve the performance,which was higher than that of the traditional TiO₂ based devices.In second chapter,studies on the mechanism of performance improvement of SnO₂ based perovskite solar cells after SnCl₄ modification from the perspective of interface modification.The influence of the perovskite layer on the subsequent performance analysis was avoid by change the fabrication process of the perovskite layer with increased crystalline quality.Then a series of physical devices were constructed to analyze the interface contact with or without the SnCl₄ modification,the contact types of the modified devices were improved to be ohmic contact by Schottky contact through the dark I-V test,and the SnO₂ based perovskite solar cells was simulated by the diode equivalent model,analysis shows that the series resistance decreased and the internal recombination decreased after SnCl₄ modification.A series of SnCl₄ modification?none,10,20 and 30 minutes,respectively?devices,were fabricated,the best photovoltaic conversion efficiency was obtained based on the 30 minute modified device?average 16.19%,up to 17.14%?.The PL spectrum test showed that with the increase of the modification time,the interface recombination of the device was decreased,hysteresis test also shows that the hysteresis effect of the device has been gradually reduced with the stability improved.