Four-terminal perovskite/silicon series solar cells with 28% efficiency achieved by suppressing edge recombination
Authors: Fang Zheng , Zhang Fei , Qin Xiao-Jun , Yang Liu , Jin Yong-Bin , Zhou Yang-Ying , Wang Xing-Tao , Liu Yun , Xie Li-Qiang , Wei Zhan-Hua ,   China Huaneng Clean Energy Research Institute, Beijing 102209, China,   Institute of Luminescent Materials and Information Displays, Huaqiao University, Xiamen 361021, China,   Institute of Manufacturing Engineering, Huaqiao University, Xiamen 361021, China
Published: December 2022

Although the commercial application of solar cells pursues scalable and large-area devices, small-area solar cells on a scale of several centimeters possess many advantages such as low fabrication cost and facile high-throughput screening in the research laboratory. Most emerging photovoltaic technology starts from the studying of small-area devices. Recently, perovskite/silicon tandem solar cells have aroused extensive research interest because they can break through the radiative efficiency limit of single-junction solar cells. However, when commercial large-area silicon cells are cut into small pieces with a few squared centimeters in area for laboratory use, there occurs a significant efficiency loss, limiting the performance of tandem cells. Herein, to eliminate the thermal damage caused by the traditional laser cutting method and also reduce the non-radiative recombination of heterojunction silicon cells after being cut, a cold-manufacturing method of grinding wheel dicing is used to cut heterojunction silicon cells. This method is realized by high-speed mechanical grinding accompanied by liquid washing, which avoids damaging the edge of solar cell caused by heat. Compared with the device cut by laser, the heterojunction silicon cells cut by the cold-manufacturing method exhibit less cross-sectional damage. The measurements by scanning electron microscopy (SEM) and three-dimensional optical profilometer reveal that the morphology of the device edge is smoother than the counterpart cut by laser. Device physics measurements including electrochemical impedance spectrum(EIS), dark current-voltage curves, transient photovoltage (TPV), transient photocurrent (TPC), and the dependence of short-circuit current density and open-circuit voltage on light intensity reveal that the cold-manufacturing method can significantly prevent the heterojunction silicon cells from non-radiatively recombining after being cut. These results indicate that the edge-recombination of the silicon solar cells cut by grinding wheels is reduced compared with that cut by laser. As a result, statistical analysis of the device performance reveals that both the open-circuit voltage and fill factor of the device are improved, and the average photoelectric conversion efficiency increases by an absolute efficiency of ~1%. Stacking the obtained silicon cells with the normal transparent perovskite solar cells, the obtained four-terminal perovskite/silicon tandem solar cells deliver an efficiency of over 28%. This work emphasizes the importance of reducing efficiency loss during manufacturing the heterojunction silicon solar cell in fabricating high-performance silicon-based tandem solar cells.