Ganghyun Park

Indium phosphide (InP)‐based quantum dots (QDs) are cadmium (Cd)‐free emitters for display applications, but their operational stability is limited by surface defects and imbalanced carrier injection. Here, we introduce a [2‐(9H‐carbazol‐9‐yl)ethyl]phosphonic acid (2PACz)‐mediated surface modification strategy for efficient and stable quantum dot light‐emitting diodes (QLEDs). 2PACz forms a mixed‐ligand surface by partially replacing native oleic acid ligands and binding to under‐coordinated surface sites, thereby reducing trap‐assisted nonradiative recombination. In parallel, 2PACz‐mediated energy‐level modulation facilitates hole injection and suppresses excessive electron injection, improving carrier balance in inverted red InP‐based QLEDs. The resulting devices achieved a peak external quantum efficiency of 23.7% and an extrapolated half‐lifetime of 217.8 h at an initial luminance of 1000 cd m ⁻² . Transient and chemical analyses reveal that 2PACz treatment stabilizes carrier dynamics and suppresses interfacial degradation under electrical stress. This work shows that surface ligand design can improve operational stability of Cd‐free QLEDs by coupling QD surface passivation with carrier balance control.

Memristors enable parallel computation in next‐generation memory systems. Among the materials investigated, colloidal quantum dots (QDs) are attractive owing to their size‐tunable electronic structure, solution processability, and versatile surface chemistry. Nevertheless, most QD‐based memristors exhibit digital resistive switching (D‐RS) with abrupt binary transitions, limiting their neuromorphic potential. Here, an InP/ZnSe/ZnS QD‐based memristor exhibiting analog resistive switching (A‐RS) is demonstrated through a multilayer ZnO/QD/ZnO architecture engineered to promote uniform areal charge trapping. ZnO nanoparticle interlayers enhance electron transport, block hole injection to suppress recombination, and induce interfacial trap sites via controlled oxidation of the QD surface. Additional thinning of the QD layer mitigates vertical trap accumulation, ensuring stable and spatially distributed conduction. The resulting device exhibits robust trap‐controlled A‐RS and reproduces synaptic behaviors, including excitatory/inhibitory postsynaptic currents and long‐term potentiation/depression. Benchmarking with hardware‐level neural network simulations demonstrates excellent performance, achieving recognition accuracies of 92% in the multilayer perceptron model and 87.3% in the convolutional neural network trained on the CIFAR‐10 dataset, both approaching the performance of an ideal memristor. These results establish a viable pathway for exploiting the intrinsic properties of colloidal QDs in high‐performance memristors, demonstrating clear advantages over conventional D‐RS counterparts and underscoring their potential for neuromorphic compute‐in‐memory architectures.

Colloidal quantum dot (QD) films inherently exhibit a high Seebeck coefficient ( α ) and low thermal conductivity ( κ ), making them attractive for thermoelectric (TE) applications. However, achieving high electrical conductivity ( σ ) while preserving these advantages remains challenging due to limited interdot coupling and high‐temperature treatments that compromise interdependent TE parameters. Herein, room‐temperature inter‐dot bridging of individual PbS QDs is demonstrated, leading to unprecedented electronic tunability and significant improvements in the n‐type TE figure of merit ( ZT ). By tailoring the hydride concentration, gradual removal of surface ligands is induced, resulting in strengthened electrical coupling, structural ordering, and n‐type doping of QD films. Consequently, σ is precisely modulated from ≈10 ⁻⁶ to ≈10 ² S cm ⁻¹ , beyond the degeneracy transition regime where the maximum power factor (PF) is achieved. Importantly, a low κ of ≈0.25 W m ⁻¹ K ⁻¹ is preserved, elucidating the preferential charge transport enhancement without compromising phonon scattering. These effects collectively yield a substantially increased PF (103 µW m ⁻¹ K ⁻² ) and ZT = 0.14 at 330 K, which are among the highest reported for n‐type TE thin‐films processed under ambient conditions. This strategy provides a scalable, universal pathway for optimizing TE transport properties in QD‐based devices, offering strong potential for flexible thermoelectric applications.

Quantum dot light-emitting diodes (QLEDs) with high form factor are attracting great attention owing to the superb optoelectrical properties of quantum dots (QDs) and their ubiquitous application, such as wearable displays. However, there have been significant challenges in increasing the brightness of flexible QLEDs due to the inferior thermal conductivity of conventional flexible substrates. In this work, we demonstrate bright, flexible, and waterproof top-emitting QLEDs based on InP/ZnSe/ZnS QDs, which are promising for human-interfaced wearable displays. We adopted an Al foil substrate with high thermal conductivity, which can quickly dissipate the Joule heat generated at high current densities, and a Parylene C/SU-8 bilayer thin-film on both sides of the QLEDs to ensure the surface planarization and to prevent moisture permeation. As a result, the flexible QLED works well even when bent or in contact with water with a maximum luminance of ∼40000 cd/m ² . We believe that our device design strategies can contribute to the development of next-generation flexible optoelectronics.

This paper aims to discuss the key accomplishments and further prospects of active-matrix (AM) quantum-dot (QD) light-emitting diodes (QLEDs) display. We present an overview and state-of-the-art of QLEDs as a frontplane and non-Si-based thin-film transistors (TFTs) as a backplane to meet the requirements for the next-generation displays, such as flexibility, transparency, low power consumption, fast response, high efficiency, and operational reliability. After a brief introduction, we first review the research on non-Si-based TFTs using metal oxides, transition metal dichalcogenides, and semiconducting carbon nanotubes as the driving unit of display devices. Next, QLED technologies are analyzed in terms of the device structure, device engineering, and QD patterning technique to realize high-performance, full-color AM-QLEDs. Lastly, recent research on the monolithic integration of TFT–QLED is examined, which proposes a new perspective on the integrated device. We anticipate that this review will help the readership understand the fundamentals, current state, and issues on TFTs and QLEDs for future AM-QLED displays.