Solution-processed lead sulfide quantum dots (PbS QDs) are very attractive as NIR-active semiconductors for the fabrication of cost-efficient optoelectronic devices. To control the thin film carrier transport, as well as stability, surface passivation is of crucial importance. Here, we present the successful surface passivation of PbS QDs by the formamidinium lead iodide (FAPbI3) ligand. An effective procedure for the fabrication of FAPbI3-passivated PbS QDs through a binary-phase ligand exchange protocol in hexane and n-methylformamide is demonstrated. It is shown that this solution-processed ligand exchange drastically changes the photoluminescence intensity, exciton recombination dynamics, and carrier lifetime of the nanocrystals. The solution casting of the ligand-exchanged nanocrystals into thin films results in the periodic ordering of QDs in a square superlattice with close contacts. Planar graphene/QD photodetectors fabricated with PbS QDs passivated with FAPbI3 show substantially increased thermal stability as compared to similar devices using PbS QDs passivated with commonly used methylammonium lead iodide.

CoTiO3 particles with mirror-like facets were employed as the mono- and bi-layered scattering films into nanoparticle TiO2 DSSCs.

Metal halide perovskite nanoparticles have recently attracted immense interest for photodetectors due to their outstanding optical and electronic properties such as high carrier diffusion length, tunable band gap (light absorption range), and high photoluminescence (PL) efficiency. Although significant progress has been achieved in the development of perovskites, their stability is yet to be addressed. To improve the stability and quantum efficiency of FAPbI3 perovskite nanocrystals, we present a room temperature protocol to fabricate fully passivated and stable FAPbI3 nanocrystals via 2D growth in the presence of amine ligands and an excess amount of the organic cations. The crystallization mechanism of 2D colloidal quantum wells (QWs) with long-time stability is ascribed to the excess amount of large organic cations which isolate the inorganic lattice octahedral layers. It is demonstrated that the QW films (130 nm) hold 90% of their PL intensity after 30 days, which is ∼8 times more stable than FAPbI3 quantum dot (QD) films. We also show the enhanced photoresponsivity of QW photodetectors (up to 100%) as compared with QD devices. The long-term ambient performance of perovskite QW photodetectors on account of their hydrophobicity is demonstrated. The findings can shed light on a way to develop ambient stable QW nanoparticle perovskite optoelectronic devices.