Sputtering Preparation Of Indium Oxide-based TCO Intermediate Connection Layer And Its Application In Tandem Solar Cell

The silicon/perovskite tandem solar cells consists of the bottom crystalline silicon solar cells and the top perovskite solar cells connected in series by an intermediate connecting layer.The conversion efficiency of tandem solar cells can go beyond 40%,which is of great research interest and high potential for industrial application.The intermediate connecting layer is important for highly efficient tandem solar cells,and plays a decisive role in the cells performance.Transparent conductive oxide(TCO)thin film is one of the most popular candidate for the intermediate connecting layer.In this study,the magnetron sputtering method was used to prepare transparent conductive oxide thin film,including tin-doped indium oxide(ITO)and titanium-doped indium oxide(ITiO).The influence of sputtering power and substrate temperature on the optical and electrical properties of TCO films has been systematically investigated.Given the structure of silicon/perovskite tandem solar cells,the TCO film is used as the transparent window layer for the top perovskite solar cells and the intermediate connecting layer.(1)The influence of sputtering power and substrate temperature on the structure and photoelectrical performance of ITO and ITiO films has been studied.It is found that the substrate temperature has a more significant effect on the crystalline growth of ITO and ITiO materials than that of sputtering power.The conductivity of ITO or ITiO thin films increases with the increase of sputtering power(30-180 W)or substrate temperature(30-350℃).The increase of conductivity with substrate temperature is mainly due to the increase of carrier mobility.The average transmittance of ITO or ITiO thin films in the wavelength range of 300-800 nm increases with increasing substrate temperature.And the transmittance in the wavelength range of 800-1400 nm is greater than 70%.This is beneficial to increase the photo-generated current of the bottom cells.By optimizing the sputtering process,an ITO film with a conductivity of 3.7 × 103 S/cm and a band gap of 3.95 eV was obtained.(2)In tandem solar cells,the top cell is a bificial perovskite solar cell.ITO is used as the window layer for the top cell.It is proven that the introduction of molybdenum oxide(MoOx)buffer layer at the interface of ITO and hole transport layer can effectively suppress the damage to the hole transport layer during the ITO sputtering process.By optimizing the thickness of MoOx buffer layer(10-15 nm),the fill factor and short-circuit current density of the perovskite solar cell reach the optimal value,as well as the cell conversion efficiency.The bificial rate of the top cell is 69.5%,which takes advantage of the anti-reflection effect of layer stack MoOx/ITO.(3)A silicon/perovskite tandem solar cells was prepared on a silicon heterojunction solar cells by sputtered ITO intermediate connecting layer and spin-coated bificial perovskite solar cell in series.This is the first two-terminal crystalline silicon/perovskite tandem solar cells prepared in our laboratory.The short-circuit current density of the tandem solar cells is 8.9 mA/cm2,the open circuit voltage is 980.6 mV,the fill factor is 40.2%,and the cell conversion efficiency is 3.5%.The cell performance is mainly limited by the current mismatch between the top and bottom solar cells,and the inferior interface between the ITO intermediate connecting layer and the crystalline silicon solar cell.It is suggested to further optimize of the photoelectric characteristics of the top perovskite solar cell and the improvement of the interface of silicon and ITO intermediate connection layer for higher efficiency of silicon/perovskite tandem solar cells.This paper systematically studied the influence of sputtering power and substrate temperature on the structure and photoelectrical performance of ITO and ITiO films.The application of ITO film in crystalline silicon/perovskite tandem solar cells was explored.This is the first two-terminal crystalline silicon/perovskite tandem solar cells prepared in our laboratory.