Benzyl viologen dichloride as a novel ligand for CdSe CQDs in hybrid QDs/organic photodiodes

[Display omitted] •Introducing benzyl viologen dichloride (BVD-Cl) as a new ligand for CdSe QDs surface passivation.•BVD-Cl enables the creation of a stable CdSe quantum film with reduced interdot spaces and preserved quantum confinement.•Hybrid photodiode with BVD-Cl:CdSe quantum film exhibited high sensitivity to light stimuli.•BVD-Cl is a promising alternative to traditional ligands for creating CQD films with improved charge transport for optical sensing systems. The use of colloidal quantum dots (CQDs) in advanced optoelectronic devices requires the substitution of bulky long ligands with short organic ligands. The search for a short-ligand that can create stable quantum solids without compromising the confinement of the CQDs is of paramount importance. Within this context, we present a novel surface passivation ligand, benzyl viologene dichloride (BVD-Cl), as a replacement for the conventional trioctylphosphine oxide (TOPO) capping of CdSe CQDs. BVD-Cl enables the creation of a CdSe quantum solid while retaining quantum confinement. To demonstrate the efficacy of this ligand-exchange process, we utilised Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectrometry (EDX), high-resolution transmission electron microscopy (HR-TEM), and X-ray photoemission spectroscopy (XPS). We then implanted the new BVD-Cl:CdSe quantum film as the main inorganic QDs layer into a hybrid photodiode combined with poly 3-hexylthiophene (P3HT) as the organic layer. The photodiode demonstrated high sensitivity to light stimuli and rectifying behaviour, with a responsivity of 70 mA/W at 550 nm. Our observations imply that using BVD-Cl as a surface passivation ligand for CQDs has significant implications for the development of advanced optoelectronic devices.