Libai Huang

The spin-entangled triplet-pair state produced by singlet fission is promising for quantum information applications, but its optical darkness severely limits spectroscopic access and optical readout. Here we show that monolayer WS₂ can act as a long-range excitonic sensitizer for triplet-pair emission in the singlet-fission molecule 6,13-bis(triisopropylsilylethynyl)-tetramethyl pentacene (TCPS). Strong excitonic resonances and spin–orbit–split valleys in WS₂ mediate long-range excitonic energy transfer into the triplet-pair manifold, enhancing triplet-pair emission by more than two orders of magnitude. This enhancement arises from the exceptionally large exciton transition dipole moment of WS₂, which enables efficient dipole–dipole coupling across the hybrid interface. Temperature-dependent and time-resolved spectroscopy reveals ultrafast picosecond energy transfer. Distance-dependent measurements demonstrate efficient transfer beyond 100 nm, inconsistent with classical Förster scaling and instead indicative of radiative, near-field–assisted coupling with a shallow ~ 1/d dependence. These results establish a mechanism for long-range triplet-pair sensitization in hybrid molecular/transition-metal dichalcogenide heterostructures and provide a route for coupling correlated multiexciton states to optically active excitonic materials.

Spatially heterogeneous interfacial energetics, often originating from residual lead iodide (PbI₂), represent a fundamental bottleneck to both the efficiency and operational stability of perovskite photovoltaics. Conventional PbI₂ passivation strategies based on monodentate ligands or highly polar solvents either interact weakly with PbI₂ or undesirably perturb the underlying three-dimensional perovskite lattice. Here, we report a diammonium bidentate strategy that selectively reconstructs residual PbI₂ into corner-sharing PbI₆ octahedra while preserving the bulk perovskite. Enabled by dual-site coordination, a newly designed thiophene-based bidentate ligand (MeXT) stabilizes PbI₆ units during passivation and establishes spatially homogeneous interfacial energetics. Perovskite solar cells incorporating MeXT achieve 26.19% power conversion efficiency and retain over 80% of their initial efficiency after 1000 h of continuous 1-sun illumination at 75 °C. This dual-anchor coordination passivation strategy establishes a general design principle for selectively treating residual PbI₂ and creating electronically coherent and operationally stable interfaces in perovskite photovoltaics.

Dibenzoterrylene (DBT) is a coherent molecular single-photon emitter that exhibits an interesting energetic landscape with multiple low-energy, accessible conformations. In this work, using first principle approaches, we systematically investigate the conformational landscape of DBT in the gas phase, identifying five unique conformers, four of which are expected to be thermally accessible in a solid state host. We further analyze vibrational and electronic spectroscopies to identify conformer-specific spectral signatures. We find that each conformer exhibits largely similar spectral features in both vibrational and electronic spectroscopies; however, subtle differences exist across all spectra, which highlight possible conformer-specific changes that may be able to be identified in high-resolution spectroscopic experiments. Finally, we explore the Franck–Condon–Herzberg–Teller vibrationally resolved electronic excitation spectrum which showcases even more rich conformation-specific landmarks. Collectively, our results provide a comprehensive framework for understanding how DBT’s conformer-specific electronic structure could play a role in observed optical behaviors.

Loss of coherence in a quantum subsystem by coupling it to an environment limits its applications in quantum information technology. Because of large optical absorption cross sections and high single-photon emission rates, perovskite quantum dots (QDs) have garnered considerable attention for applications in quantum information, but they are limited by loss of coherence due to electron–phonon coupling. We calculated coherence times in dimers of small cesium lead bromide QDs bridged by various ligands. Typically, QD dimers exhibit longer coherence times than the corresponding monomer due to more delocalized electronic excitations, resulting in weaker electron–phonon coupling. Dimers connected by both aliphatic and aromatic ligands exhibit extended coherence times. Aromatic ligands with states close to QD band edges can enhance interdot coupling; however, the ligand frontier orbitals and the QD band edges should not hybridize, since this allows fast ligand motions to accelerate decoherence. Exciton delocalization between QDs is reduced by structural disorder and long aliphatic ligands. Generally, improved coherence times are achieved by electronic delocalization, surface passivation, and the suppression of active phonon modes. The reported results provide guidelines for engineering perovskite QD assemblies and related materials for applications in quantum information technologies.

Realizing robust many-body exciton interactions, coherence, and long-range exciton transport is central to technologies ranging from quantum information science (QIS) to light-emitting devices and solar cells. Colloidal quantum dots (QDs) offer scalable fabrication and spectral tunability, yet performance is suppressed by inhomogeneous broadening, defects, and fast dephasing. Lead-halide perovskite QDs, exhibiting large transition dipole moments, high radiative efficiencies, and slow low-temperature dephasing, enable strong light-matter coupling and long-range dipolar exciton-exciton interactions. This review focuses on the origins and consequences of many-body exciton physics in perovskite QDs, including dipole-mediated interactions and cooperative radiative phenomena. We discuss how exciton fine structure, inter-QD electronic coupling, and exciton-phonon interactions govern coherence and the role of disorder. We then examine exciton transport in QD solids, emphasizing the crossover from coherent motion enabled by delocalized excitonic wave functions to dephasing-driven incoherent hopping. Finally, we survey routes toward scalable many-body states through nanophotonic integration.

High-performance microphotodetectors require materials that combine strong light–matter interaction, fast charge transport, and ambient stability. Here, we demonstrate single-nanowire devices based on the 2D perovskite (TPA3)₂PbBr₄, synthesized via a controlled slow-cooling self-assembly process that yields defect-minimized, anisotropic nanowires with smooth facets. These microphotodetectors exhibit ultralow dark currents (∼10^–15 A), high responsivity (up to 156 mA W^–1), and exceptional specific detectivity (∼10¹¹ Jones) under near-UV (405 nm) illumination, with rise and fall times in the millisecond regime. The superior detectivity is primarily driven by the suppression of thermal noise through the material’s ultralow dark current, while the millisecond temporal response is governed by high-intensity trap-filling dynamics. The devices maintain stable operation over 4000 s of continuous on/off cycling and show remarkable ambient stability over weeks, attributed to dense crystal packing and robust organic cation layers. Furthermore, the influence of nanowire thickness on the charge collection efficiency is systematically elucidated through optical penetration depth analysis, highlighting design principles for optimizing low-dimensional perovskite photodetectors. This study introduces single 2D perovskite nanowires as a versatile platform for miniaturized, high-performance optoelectronic devices.

We present a hybrid solid-state cavity quantum electrodynamics (QED) platform that integrates a high density of coherent organic molecules with high-quality-factor nanophotonics. Thin anthracene crystals doped with dibenzoterrylene (DBT) are mechanically transferred onto prefabricated silicon nitride photonic crystal cavities, preserving both the cavity quality and molecular coherence. This approach decouples emitter synthesis from nanofabrication, providing a pathway for integrating other types of emitters. The high density of molecular emitters results in up to ten molecules being coupled to a single cavity. By tuning pairs of molecules into resonance within a single cavity mode, we observe cavity-mediated interactions in both dispersive and dissipative regimes. These results establish an accessible route to deterministic on-chip single- and multiphoton sources.