Metal Microgrid Embedded Transparent Electrode for Enlarge Perovskite Solar Cells

Organic-inorganic hybrid perovskite (OIHP) solar cells have attracted much attention as next-generation energy devices. In the fabrication of OIHP solar modules, the unit cells are designed by considering the charge carrier loss in the collection process through transparent electrodes. However, in the modularization process of OIHP solar cells, the optical dead area increases, resulting in the degradation of the overall module efficiency. To mitigate the efficiency loss, it is crucial to enlarge the size of the unit cells. However, as the unit cell size increases, the power loss due to the inherent electrical resistance of transparent electrodes also becomes more critical, leading to a decrease in the fill factor (FF) of OIHP solar cells and modules. For example, when the voltage and current density at the maximum power point of the OIHP solar cell is 1.0 V and 23.5 mA/cm², respectively, the power loss will become the same as the overall photo-generated power when the carriers need to move over 3.5 cm to be collected through the ITO layer which has a sheet resistance of 10 ohm/sq. Therefore, the lower sheet resistance of transparent electrodes would be essential to realize the larger-sized OIHP solar cells. Here, we report a hybrid transparent electrode in which a metal microgrid is embedded into the glass substrate, and ITO covers the substrate. The hybrid electrodes exhibit excellent sheet resistance of lower than 1 ohm/sq and comparable optical transmittance (~82%, @300-800 nm) to that of ITO/glass substrate (~83%, @300-800 nm). When utilizing the developed hybrid electrode, the OIHP single solar cell with a size of 12.25 cm² shows an open-circuit voltage of 1.04 V, a short-circuit current density of 20.1 mA/cm², FF of 65.8%, and an overall efficiency of 13.8%. In particular, the FF of the OIHP solar cell based on the hybrid electrode is 2.01 times higher than that of the OIHP single solar cells based on an ITO/glass substrate (32.7%), confirming that charge carriers are collected efficiently. Our work suggests enormous potential for significant performance improvement of large-scale OIHP solar cells.