Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) thin film is widely used as a hole injection layer (HIL) in quantum-dot (QD) light-emitting diodes (LEDs). However, its acidic and hygroscopic nature erodes the indium tin oxide electrode, causing serious device stability issues. To overcome the limitations, QLEDs that utilize self-assembled molecules (SAMs) as the HILs have been proposed and demonstrated, offering both high efficiency and improved stability. The 4PADCB SAM forms a high-quality film characterized by excellent transmittance and low surface roughness. Crucially, it possesses a high work function, which facilitates effective hole injection into the QD layer, thereby improving charge balance and reducing the accumulation of excess charges within the QLED. Additionally, the 4PADCB’s shallow lowest unoccupied molecular orbital energy level prevents electron leakage towards the anode. As a result, the 4PADCB-based red QLED exhibits a maximum external quantum efficiency of 28.07%, a peak power efficiency of 37.24 lm/W, and an extended T₉₅ operational lifetime of 12,401 h at 1000 cd/m², significantly outperforming the device based on PEDOT:PSS. This SAM HIL approach paves the way towards commercially viable, high-performance QLEDs in next generation displays.

Owing to their strong nonlinearity, cadmium sulfide (CdS) nanostructures are promising platforms for investigating the fundamental physics of light–matter interactions. However, observing the strong exciton–photon interactions in CdS microstructures at room temperature continues to present significant challenges, primarily because of the limited exciton binding energy. This study reports the direct observation of the interaction between excitons and microcavity photons in Sn-doped CdS microsheets without extreme fabrication conditions. Using angle-resolved photoluminescence (ARPL) spectroscopy, Rabi splitting of polaritons up to 163 meV was obtained at room temperature. Additionally, the temporal lasing dynamics of the Sn-doped CdS microsheets were investigated using a streak camera system. Most importantly, exciton–polariton condensation and coherent exciton–polariton lasing in the Sn-doped CdS microsheet was observed at room temperature. These results advance the fundamental understanding of exciton–polaritons in Sn-doped CdS microsheets and their applications in miniaturized microlaser devices.

Although quantum-dot light-emitting diodes (QLEDs) can exhibit high efficiency and long lifetime, the realization of QLEDs-based displays remains challenging due to their complex multilayer architectures and the use of unstable poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) hole injection layer (HIL). Here, we develop a novel trilayer p-type/intrinsic/n-type (PIN) QLED with only three functional layers: PTAA:TFB:F4-TCNQ (PTAA: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]; TFB: poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine)]; F4-TCNQ: 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) bulk-heterojunction (BHJ) hole transport layer (HTL), quantum-dot emitting layer, and ZnMgO electron transport layer. Due to well-matched energy level, increased hole transport path from PTAA to TFB, and improved hole density and enhanced hole mobility of the PTAA:TFB:F4-TCNQ BHJ HTL, the resultant trilayer PIN QLED exhibits a high external quantum efficiency (EQE) of 25.1% and an impressive peak brightness of 382,600 cd/m², which are significantly higher than those of the control QLED. Moreover, the trilayer PIN QLED also shows a 1.94-fold longer operational lifetime than control QLED due to the improved device performance, reduced charge accumulation, and removal of unstable PEDOT:PSS. The developed trilayer PIN QLED, with fewer functional layers and better stability, could promote the practical application of QLED in displays and solid-state lighting.

Sb-based organic–inorganic hybrid metal halides (OIHMHs) with [SbCl₅]²⁻ units have been widely reported due to high photoluminescence quantum yield (PLQY) and occasional multiple self-trapped exciton (STE) emission bands mainly out of singlet and triplet states, and their multi-band emission is important in white light-emitting diode (WLED). However, not all these OIHMH compounds can produce both emissions out of singlet STE and triplet STE at room temperature simultaneously. It is crucial to consider how the singlet STE generates and retains to emit light at room temperature for this material’s design and application. Herein, a strategy is proposed that can significantly lift Sb halide PLQY by synthesizing two Sb-based OIHMHs using organic amine cations of different-sized and -quantity, which modulate the distance of neighboring emission centers. Therein, the occurrence of singlet STE emission is found to be closely related to the distance of [SbCl₅]²⁻ units and local unit distortion in the lattice. The larger distance can produce smaller local distortions, favoring the formation of the singlet STE emission band at higher energy. This is the first work to reveal the relationship between the local structure and the origin of the singlet STE emission band, providing new insights into the modulation of the Sb-based OIHMH’s emission.

Perovskite variants have attracted wide interest because of the lead-free nature and strong self-trapped exciton (STE) emission. Divalent Sn(II) in CsSnX₃ perovskites is easily oxidized to tetravalent Sn(IV), and the resulted Cs₂SnCl₆ vacancy-ordered perovskite variant exhibits poor photoluminescence property although it has a direct band gap. Controllable doping is an effective strategy to regulate the optical properties of Cs₂SnX₆. Herein, combining the first principles calculation and spectral analysis, we attempted to understand the luminescence mechanism of Te⁴⁺-doped Cs₂SnCl₆ lead-free perovskite variants. The chemical potential and defect formation energy are calculated to confirm theoretically the feasible substitutability of tetravalent Te⁴⁺ ions in Cs₂SnCl₆ lattices for the Sn-site. Through analysis of the absorption, emission/excitation, and time-resolved photoluminescence (PL) spectroscopy, the intense green-yellow emission in Te⁴⁺:Cs₂SnCl₆ was considered to originate from the triplet Te(IV) ion ³P₁→¹S₀ STE recombination. Temperature-dependent PL spectra demonstrated the strong electron-phonon coupling that inducing an evident lattice distortion to produce STEs. We further calculated the electronic band structure and molecular orbital levels to reveal the underlying photophysical process. These results will shed light on the doping modulated luminescence properties in stable lead-free Cs₂MX₆ vacancy-ordered perovskite variants and be helpful to understand the optical properties and physical processes of doped perovskite variants.