Abstract
Recently, inorganic CsPbI(2)Br perovskite is attracting ever-increasing attention for its outstanding optoelectronic properties and ambient phase stability. Here, an efficient CsPbI(2)Br perovskite solar cell (PSC) is developed by: 1) using a dimension-grading heterojunction based on a quantum dots (QDs)/bulk film structure, and 2) post-treatment of the CsPbI(2)Br QDs/film with organic iodine salt to form an ultrathin iodine-ion-enriched perovskite layer on the top of the perovskite film. It is found that the above procedures generate proper band edge bending for improved carrier collection, resulting in effectively decreased recombination loss and improved hole extraction efficiency. Meanwhile, the organic capping layer from the iodine salt also surrounds the QDs and tunes the surface chemistry for further improved charge transport at the interface. As a result, the champion device achieves long-term stabilized power conversion efficiency beyond 14%.