Noncovalent functionalization of hole-transport materials with multi-walled carbon nanotubes for stable inverted perovskite solar cells†
Novel binaphthylamine-based hole-transport molecules with different side-chains were designed and synthesized. The obtained materials exhibit comparable optoelectronic properties and molecular configuration, but distinct film properties. In this work, which was inspired by the structural feature of polymer and π–π stacking strategy of carbon nanotubes with large π-spacers, two kinds of optimized hole-transport molecules with amine and methyl units were attached to multi-walled carbon nanotubes by physisorption, and were further used to fabricate inverted perovskite solar cells. A non-encapsulated device based on a hole-transporting material with multi-walled carbon nanotubes gives a power conversion efficiency of 17.17%, comparable to that of the pristine hole-transport material (17.32%). More importantly, the former exhibits a higher device stability than the later. Introduction of carbon nanotubes to hole-transport materials provides a new method for improving the device stability of inverted perovskite solar cells.