Research On ITO-free Solar Cells Based On Metal Grids Anodes

Organic-inorganic hybrid methylammonium lead trihalide perovskites have attracted more attentions for low-cost and high efficiency solar cells,which is due to their advantages of high absorption coefficient,large light absorption range,long charge carrier diffusion length,bandgap tunability,bipolar transport properties and so on.Nowadays,indium thin oxide?ITO?is the most commonly used transparent electrodes of perovskite solar cells?PSCs?.However,ITO shows the drawbacks of brittleness.It is not an ideal candidate for flexible electrodes.In contrast,metal grids have excellent ductility and can be easily fabricated by e-beam evaporation,which is suitable for large-area device production.More importantly,its conductivity and transmittance can be adjusted by grid parameters such as the width and thickness.Therefore,metal grid is a competitive flexible electrode material.In this work,we used photolithography processed Ni/Au metal grids to replace ITO as the transparent electrode.The main contents are as follows:1.Designed a high-quality Ni/Au metal grids transparent electrode,and researched its transmission,conductivity and interfacial properties.Ni is used to improve the adhesion of metal mesh to glass substrate.Au is used to improve the conductivity of metal grids.The charge collection ability of metal grids is enhanced by conductive polymer PH1000.A hexagonal Ni?30 nm?/Au?10 nm?/PH1000 metal grids transparent electrode with a line width of 5?m was obtained by optimizing the line width,thickness,shape and other structural parameters as well as photolithography parameters.2.A planar structure perovskite solar cell with an effective area of 0.09 cm² was successfully prepared on the metal grids electrode.The power conversion efficiency PCE is 13.88%,the open circuit voltage V_OC is 0.94 V,the short circuit current J_SC is 21.14 mA/cm²,the fill factor FF is 0.70.It also showed good steady-state output characteristics and process repeatability.At the same time,the grid-based devices achieved the same photovoltaic performance as the ITO based reference devices?PCE=15.7%?,which showed the metal grid is a very competitive ITO alternative electrode.3.A large-area perovskite solar cell based metal grids with area of 1 cm² was further developed based on the low-temperature solution process.The PCE is 6.01%,the V_OC is1.04 V,the J_SC is 11.28 mA/cm²,the FF is 0.51.It also showed good steady-state output characteristics and process repeatability.The results showed that the metal grid electrodes have great potential in the field of large-area and flexible perovskite solar cells.And analyzed the reason for performance degradation with enlarging device area.Moreover,excepted the development of high performance and large-area perovskite solar cells by interface engineering and preparation technology.