28.3%-efficiency perovskite/silicon tandem solar cell by optimal transparent electrode for high efficient semitransparent top cell

Perovskites with tuned bandgap provide an attractive opportunity to realize perovskite/silicon tandem solar cells that offer tremendous potential in exceeding the intrinsic power conversion efficiency (PCE) of each subcell. The transparency and conductivity of the top electrode for top cell are the main keys in tandem solar cell. Here, we demonstrate a continuous, ultrathin Au film as the top electrode by introducing a Cr seed layer, which improves the efficiency of semitransparent perovskite devices and tandem solar cells. The Cr seed layer has large surface energy, which induces Au growth according to the Frank-van der Merwe principle to form a continuous, ultrathin film with exciting transmittance and conductivity. As a result, the highest PCE of 19.8% for semitransparent perovskite cells is achieved. The simulated optical field distribution by COMSOL and experimental results reveal that the semitransparent perovskite device has high transmittance in the near-infrared range, demonstrating that it is optimal top cell in a tandem solar cell with a silicon heterojunction device. The tandem solar cell, with the semitransparent perovskite top cell mechanically stacked on the silicon heterojunction bottom cell, demonstrates a PCE of 28.3%. This breakthrough in the design of the tandem cell architecture based on a transparent electrode offers an efficient route towards the transition of perovskite and tandem solar cells.