Polyaromatic Nanotweezers on Semiconducting Carbon Nanotubes for the Growth and Interfacing of Lead Halide Perovskite Crystal Grains in Solar Cells

Perovskite crystal grain size control, grain boundary passivation, and grain bridging are the keys to obtaining high efficiency in perovskite solar cells. A small amount of semi-conducting single-walled carbon nanotubes added to a perovskite active layer can achieve this. In particular, the surfactants attached to the semiconducting single-walled carbon nanotubes a crucial role. In this work, we synthesized a new surfactant, 4,6-di(anthracen-9-yl)-1,3-phenylene bis(dimethylcarbamate), which has a polyaromatic group on one end and a urea-analogue carbamate group on the other end. The polyaromatic anthracene end functions as a nanotweezer clenching the carbon nanotubes strongly via pi-pi interaction while the carbamate end interacts with Pb2+, functioning as a strong Lewis base. In addition, the new surfactant has conjugated double bonds with a suitable bandgap, resulting in enhanced charge mobility in the perovskite film. Overall, the new surfactant-clenched semiconducting carbon nanotubes showcase superior effectiveness as passivators and charge bridges in perovskite solar cells as compared to the conventional deoxycholate surfactant-wrapped semiconducting single-walled carbon nanotubes. The new surfactant-attached semiconducting carbon nanotube-added NH3CH3PbI3-based perovskite solar cells exhibited a power conversion efficiency of 20.7%, which is higher than that of the reference devices with no additives (18.4%) and the previously reported semiconducting single-walled carbon nanotube-added devices (19.7% in this work and 19.5% in the literature).