Multiple Exciton Generation on Doped Wide‐Band Semiconductor Photoanode with Hierarchical Quantum Structure

Abstract The multiple exciton generation (MEG) effect, which produces multiple photo‐generated charge carriers from a single high‐energy photon absorption by a semiconductor with a narrow bandgap, has the potential to revolutionize photovoltaic, photoelectric detection, and other technologies. Here, this work finds that the surface carbon‐modified wide‐bandgap photoanode with hierarchical quantum structure can drive a photoelectrochemical reaction with a quantum efficiency exceeding 145% by the first time. More studies reveal that the presence of the MEG effect in the MEG‐CdS photoanode is attributed to the formation of high‐quality surface C‐modified CdS quantum nanosheets on CdS bulk film by in situ, this hierarchical quantum structure leads to quantum confinement effects that increase effective Coulomb interaction for driving MEG and decrease competition for thermal exciton cooling. The acceptor level introduced by carbon reduces the MEG threshold (approximately twice the energy level difference) and collaborates with the built‐in electric field of the C‐CdS/bulk‐CdS homojunction to enable the effective generation and separation of photo‐generated charge carriers. The internal quantum efficiency of the MEG‐CdS photoanode reaches up to a recording value of 145%, providing a novel perspective on the contribution of surface‐modified wide‐band semiconductors and their quantum effects in the application of MEG.