Bottom-Up Fabrication of BN-Doped Graphene Electrodes from Thiol-Terminated Borazine Molecules Working in Solar Cells
Carolina M. Ibarra‐Barreno, Sanchari Chowdhury, Martina Crosta, Tashfeen Zehra, Francesco Fasano, Paromita Kundu, Jenthe Verstraelen, Sara Bals, Mohammed Subrati, Davide Bonifazi, Rubén D. Costa, Petra Rudolf
Abstract
Graphene exhibits exceptional properties, including high tensile strength, mechanical stiffness, and electron mobility. Chemical functionalization of graphene with boron and nitrogen is a powerful strategy for tuning these properties for specific applications. Molecular self-assembly provides an efficient pathway for the tailored synthesis of doped graphene, depending on the molecular precursor used. This study presents a scalable approach to synthesizing large-area boron- and nitrogen-doped graphene using two borazine precursors bearing thiol functionalities. After self-assembly on electropolished polycrystalline copper foil, the precursors undergo photopolymerization under UV irradiation, and subsequent annealing in vacuum transforms the cross-linked BN-doped layer into a graphenoid structure. X-ray photoelectron spectroscopy confirms the integration of the borazine rings into the BNC architecture, while Raman spectroscopy reveals a red shift in the characteristic G bands along with intense and broad D bands, highlighting boron-nitrogen contributions. Transmission electron microscopy provides insight into the morphology and structural quality of the BNC films. The BNC films were successfully integrated as counter electrodes in dye-sensitized solar cells, achieving a power conversion efficiency of up to 6% under 1 sun illumination and 11.8% under low-intensity indoor ambient light. Hence, this work not only establishes a straightforward, controllable route for heteroatom doping but also introduces a novel concept of Pt-free counter electrodes for efficient indoor energy harvesting applications.