Highly efficient inverted hole-transport-layer-free perovskite solar cells

Abstract

In the past ten years, perovskite solar cells (PSCs) have achieved tremendous success, with the efficiency rivalling that of conventional silicon-based devices. To promote commercialization, lowering the production cost and reducing the complexity of the process would make the devices more competitive and thus are highly required. In this respect, inverted hole-transport-layer-free (HTL-free) PSCs were developed and have been attracting extensive attention. To date, the efficiency of inverted HTL-free PSCs has surpassed 20%, and 90% of the initial efficiency can be retained after 1000 h of continuous illumination, showing their great application potential. In this mini-review, we summarize the development and progress of inverted HTL-free PSCs. The universality of inverted HTL-free structures (including flexible and semi-transparent devices) and stability are also discussed. Finally, promising research directions are suggested to further advance the inverted HTL-free PSCs.