Highly efficient wide-band-gap perovskite solar cells fabricated by sequential deposition method

Perovskite-based double junction tandem solar cells, including perovskite/silicon, perovskite/perovskite, and perovskite/Cu(In, Ga)Se2, have received increasing attention in recent years. While most wide-band-gap perovskite solar cells so far were synthesized by the one-step deposition method which has a simple procedure but is hindered by its narrow antisolvent dripping time window, exploration of other method is in demand. In this study, a highly efficient wide-band-gap perovskite solar cell device with a bandgap of 1.63-1.65 eV has been successfully fabricated using the two-step sequential deposition method by optimizing the solution composition and the spinning speed of the second step. The best solar cell obtained has a power conversion efficiency of 20.35% and a fill factor (FF) of 81.53%, and is believed to be the first wide-band-gap solar cell device fabricated by the sequential deposition method with an efficiency over 20%. The obtained FF value is also pretty high among all reported perovskite solar cells fabricated by sequential deposition method. Our work indicates that sequential deposition method not only can be applied to the traditional narrow-band-gap perovskite solar cells but also has a potential for fabricating highly efficient wide-band-gap perovskite solar cells.