Suppressing Edge-recombination Enables 28%-efficient Four-terminal Perovskite/Silicon Tandem Solar Cells

Although the commercial application of solar cells pursues scalable and large-area devices, small-area solar cells in the 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 start from studying small-area devices. Recently, perovskite/silicon tandem solar cells have attracted extensive research interest because they can break the radiative efficiency limit of single-junction solar cells. However, when cutting commercial large-area silicon cells into small-area (square centimeters) 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 reduce the non-radiative recombination of heterojunction silicon cells after cutting, 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 edge damage of solar cells caused by heat. Compared with the devices cut by laser, the heterojunction silicon cells cut by the cold-manufacturing method exhibit less cross-sectional damage. Scanning electron microscopy (SEM) and three-dimensional optical profilometer measurements reveal that the morphology of the device edge is smoother than that cut by laser. Device physics measurements including electrochemical impedance spectroscopy (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 enables a significant inhibition of non-radiative recombination of the heterojunction silicon cells after cutting. 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.