S. Poornachandiran, D. Sengottuvelu, M. Majdoub, P. Narayan Samanta, J. Chaudhary, A.V. Sumant, N.R. Pradhan, S. Nouraniana, A. Al-Ostaz
University of Mississippi,
United States
Keywords: perovskite quantum dots, Mixed-Halide, 0D-2D heterostructure, optoelectronics, surface passivation
Summary:
Perovskite quantum dots (PQDs) are promising for advanced optoelectronic devices due to their high photoluminescence quantum yields, tunable bandgaps, and efficient light absorption. Mixed-halide systems enable further performance improvements but face long-term stability and uniformity challenges. Structural degradation arises from (a) surface defects caused by weakly bound ligands detaching and (b) halide ion migration due to low migration energy, leading to lattice vacancies. To address these issues, we focus on ligand modification and core-shell tailoring. We employed a ligand-assisted reprecipitation method to synthesize mixed-halide methylammonium lead-cadmium PQDs, precisely controlling their halide composition and stability. A dual-ligand system—oleic acid and oleylamine—was utilized to enhance surface passivation and stability. At the same time, secondary ligands such as trioctylphosphine oxide and thiol-based ligands further suppressed ion migration. Reprecipitation involves rapid nucleation and high crystallinity by injecting precursors into a nonpolar solvent with ligands. Tuning methylammonium halide ratios and lead content enables control over the bandgap and emission wavelength, achieving customizable optical properties. Experimental techniques and quantum simulations provide insights into surface chemistry and photoluminescence properties, addressing phase separation challenges in mixed-halide PQDs for photodetector applications. Additionally, we demonstrate a broadband photodetector operating from UV to NIR wavelengths using a 2D graphene/0D PQDs (2D-0D) hybrid structure. NIR-absorbing PQDs transfer charge carriers to a non-NIR-absorbing 2D graphene channel, achieving high photoresponsivity. These findings offer solutions for enhancing PQD stability and performance in next-generation optoelectronics.