Charge Transfer in Organo-metallic Halide Perovskite Thin Film/Quantum Dot Heterostructures

Organo-metallic Halide Perovskite (OMHP) thin films have been of great interest for photovoltaics due to the rate at which their power conversion efficiency (PCE) has increased, as well as for their low production cost. Perovskite quantum dots (PQDs) have also garnered interest for similar applications. However, thin films have stability issues in the presence of moisture or oxygen, and PQDs have not demonstrated high enough PCE. Some of these issues could be addressed by combining the two to form a heterostructure of PQDs layered atop an OMHP thin film. We investigated charge transfer mechanisms between spin-coated methylammonium lead iodide (MAPI) thin films and PQDs. We varied the PQD composition and surface ligands for a systematic study where the PQDs all had band gaps larger than that of MAPI, allowing for multiple routes of energy and charge transfer. Using photoluminescence (PL) spectroscopy, we found that the emission from PQDs functionalized with aliphatic ligands, was quenched while the MAPI emission intensity was increased indicating energy or charge transfer between the PQD and thin film layer. When varying the excitation energy to above and below PQD band gap, we found charge carrier recombination lifetimes were affected by the excitation energy only for films with PQDs with conducting ligands, indicating ligands played a role in the charge transfer mechanism. In addition to these studies, further investigations are in progress to better quantify the effect of charge transfer between PQDs and thin films on the electronic properties of the heterostructures.