Unique Seamlessly Bonded CNT@Graphene Hybrid Nanostructure Introduced in an Interlayer for Efficient and Stable Perovskite Solar Cells

Carbon nanomaterials have been widely used as an interlayer for realizing efficient and stable perovskite solar cells (PSCs). Theoretically, the design of a carbon composite interlayer that combines excellent conductivity with a high specific surface area is a better strategy than the application of pure nanocarbons. Here, an unusual seamlessly bonded carbon nanotube@graphene (CNT@G) hybrid nanomaterial was strategically synthesized and demonstrated to behave as an efficient interlayer for realizing efficient and stable PSCs. Due to the advantage of the seamless bond, the as-proposed hybrid nanostructure showed an apparent improvement compared to the use of CNTs only, graphene only, or a simple mixture of CNTs and graphene. The power conversion efficiency improved from 15.67% to 19.56% after introduction of the hybrid nanomaterial due to efficient carrier extraction, faster charge transport, and restrained carrier recombination. More importantly, PSCs with a CNT@G hybrid-decorated hole transport layer (HTL) showed good thermal stability during a 50 h heat-aging test at 100 °C and water stability under ambient humidity (30–50% relative humidity) for 500 h because the hybrid nanostructure exhibited an increased capability to block ion/molecule diffusion. Our results provide an alternative approach for fully exploring the potential application of nanocarbons in the development of high-performance PSCs.