Stoichiometric Engineering of Ag₂S Nanocrystals to Realize High Performance for Organic–Inorganic Hybrid Photodiodes

Organic–inorganic hybrid photodiodes (HPDs) have the potential to revolutionize optoelectronic devices for a brand-new technology. HPDs combining polymeric semiconductors and nanocrystals (NCs) have demonstrated their ability to amplify signals by trapping electrons within ligand-capped NCs. The performance of HPDs is dependent on their ability to capture minority carriers for the continuous tunneling injection of majority carriers. To achieve this, heavy-metal-free Ag2S NCs were synthesized with stoichiometric engineering for HPDs. The surface stoichiometry of the NCs was analyzed using time-resolved photoluminescence and space-charge-limited current analyses and elemental analyses. The fine-tuning of the surface stoichiometry of Ag2S NCs enables high external quantum efficiency (EQE) of the HPDs. The optimized HPDs demonstrated a high peak EQE of 170,000% and specific detectivity of 3 × 1013 Jones. Control of NC stoichiometry is vital for the photophysical properties of sensitizing centers, which guarantees successful applications of HPDs to optoelectronic devices.