Study On Photovoltaic Characteristics Of Perovskite Devices Based On Amorphous Niobium Oxide

Organic-inorganic hybrid perovskite is an emerging solution-processable optoelectronic material with excellent optoelectronic characteristics such as high extinction coefficient,appropriate band gap,long carrier life and high defect tolerance.In the past few years,the perovskite solar cells?PSCs?have developed rapidly,and the photoelectric conversion efficiency?PCE?has rapidly increased from 9.7%in 2012 to25.2%in 2019,showing a huge application potential.Electron transporting layers?ETLs?,as a key component in the separation and extraction of photogenerated electrons in devices,are essential for high efficiency and high stability PSCs.However,the TiO2 nanocrystal ETL,which commonly used in PSCs,requires high temperature?above 450°C?sintering,has low electron mobility,and is easy to catalyze the degradation of perovskite under ultraviolet light,which hinders the future flexibility and industrialization of PSCs.Amorphous NbO_x is easy to prepare through low-temperature solution method,and the high electron mobility,wide band gap,matching perovskite energy level giving it the potential to replace TiO₂ as the better ETL material.However,the easy hydrolyzed Nb salts,which are prone to cause the poor film having uniformity and high impurity defects,make the preparation of high-quality NbO_x films still challenging.This paper uses the coordination principle to control the hydrolysis of Nb salt for eliminating the internal defects and improving the quality of NbO_x film,so as to achieve high efficiency and high stability PSCs devices.The specific research contents are as follows:First,ozone?O₃?is used as a ligand for Nb⁵⁺ions.By directly passing O₃ into the Nb salt precursor solution,the O₃@NbO_x precursor has been prepared.The result shows that the strong coordination properties of O₃ and Nb ions effectively inhibit the hydrolysis of Nb salts.This on one hand make O₃@NbO_x precursor maintain a good stability under ambient condition,and obtained well compact and high repeatable NbO_x films;on the other hand,reduces the content of-OH impurities in the film and improves the purity and quality of the NbO_x film.Second,a planar heterojunction PSC device was fabricated based on NbO_x ETL,and its photovoltaic characteristics were studied.Compared with traditional NbO_x,the higher conductivity and light transmittance,lower defect state concentration and better coverage of O₃@NbO_x ETL make it exhibit better electron transmission and compound suppression capabilities.Based on these excellent photoelectric properties of O₃@NbO_x ETL,the champion PCE of 19.54%has been reached,which is significantly higher than the 15.60%of traditional NbO_x ETL based devices.Finally,based on the low-temperature preparation characteristics of O₃@NbO_x ETL,a highly efficient and flexible PSC with a PCE of 16.42%was successfully prepared.This study not only provides an efficient solution to prepare high-performance amorphous NbO_x films,but also provides a valuable reference to solve the similar low-temperature processing problems of other metal oxide semiconductor films,further promotes the development of flexible PSCs.