In situ-formed tetrahedrally coordinated double-helical metal complexes for improved coordination-activated n-doping

Reduced-Dimensional Perovskites: Quantum Well Thickness Distribution and Optoelectronic Properties

Reduced-dimensional perovskites (RDPs), a large category of metal halide perovskites, have attracted considerable attention and shown high potential in the fields of solid-state displays and lighting. RDPs feature a quantum-well-based structure and energy funneling effects. The multiple quantum well (QW) structure endows RDPs with superior energy transfer and high luminescence efficiency. The effect of QW confinement directly depends on the number of inorganic octahedral layers (QW thickness, i.e., n value), so the distribution of n values determines the optoelectronic properties of RDPs. Here, it is focused on the QW thickness distribution of RDPs, detailing its effect on the structural characteristics, carrier recombination dynamics, optoelectronic properties, and applications in light-emitting diodes. The reported distribution control strategies is also summarized and discuss the current challenges and future trends of RDPs. This review aims to provide deep insight into RDPs, with the hope of advancing their further development and applications.

Silver coordination-induced n-doping of PCBM for stable and efficient inverted perovskite solar cells

The bidirectional migration of halides and silver causes irreversible chemical corrosion to the electrodes and perovskite layer, affecting long-term operation stability of perovskite solar cells. Here we propose a silver coordination-induced n-doping of [6,6]-phenyl-C61-butyric acid methyl ester strategy to safeguard Ag electrode against corrosion and impede the migration of iodine within the PSCs. Meanwhile, the coordination between DCBP and silver induces n-doping in the PCBM layer, accelerating electron extraction from the perovskite layer. The resultant PSCs demonstrate an efficiency of 26.03% (certified 25.51%) with a minimal non-radiative voltage loss of 126 mV. The PCE of resulting devices retain 95% of their initial value after 2500 h of continuous maximum power point tracking under one-sun irradiation, and > 90% of their initial value even after 1500 h of accelerated aging at 85 °C and 85% relative humidity.

Unlocking Structurally Nontraditional Naphthyridine-Based Electron-Transporting Materials with C-H Activation-Annulation

The inherent benefits of C-H activation have given rise to innovative approaches in designing organic optoelectronic molecules that depart from conventional methods. While theoretical calculations have suggested the suitability of the 2,6-naphthyridine scaffold for electron transport materials (ETMs) in organic light-emitting diodes (OLEDs), the existing synthetic methodologies have proven to be insufficient for the construction of multiple arylated and fully aryl-substituted molecules. Herein, we present a solution for the synthesis of 2,6-naphthyridine derivatives, with the rhodium-catalyzed consecutive C-H activation-annulation process of fumaric acid with alkynes standing as the pivotal step within this strategy. The ETMs, purposefully designed and synthesized based on the 2,6-naphthyridine framework, exhibit an impressively high glass-transition temperature (Tg) of 282 °C and high electron mobility (μe), setting a new benchmark for ETMs in OLEDs with a μe exceeding 10-2 cm2 V-1 s-1. These materials prove to be versatile ETM candidates suitable for red, green, and blue phosphorescent OLED devices.

Efficient and air-stable n-type doping in organic semiconductors

Chemical doping of organic semiconductors (OSCs) enables feasible tuning of carrier concentration, charge mobility, and energy levels, which is critical for the applications of OSCs in organic electronic devices. However, in comparison with p-type doping, n-type doping has lagged far behind. The achievement of efficient and air-stable n-type doping in OSCs would help to significantly improve electron transport and device performance, and endow new functionalities, which are, therefore, gaining increasing attention currently. In this review, the issue of doping efficiency and doping air stability in n-type doped OSCs was carefully addressed. We first clarified the main factors that influenced chemical doping efficiency in n-type OSCs and then explain the origin of instability in n-type doped films under ambient conditions. Doping microstructure, charge transfer, and dissociation efficiency were found to determine the overall doping efficiency, which could be precisely tuned by molecular design and post treatments. To further enhance the air stability of n-doped OSCs, design strategies such as tuning the lowest unoccupied molecular orbital (LUMO) energy level, charge delocalization, intermolecular stacking, in situ n-doping, and self-encapsulations are discussed. Moreover, the applications of n-type doping in advanced organic electronics, such as solar cells, light-emitting diodes, field-effect transistors, and thermoelectrics are being introduced. Finally, an outlook is provided on novel doping ways and material systems that are aimed at stable and efficient n-type doped OSCs.

Unlocking the Full Potential of Electron-Acceptor Molecules for Efficient and Stable Hole Injection

Understanding the hole-injection mechanism and improving the hole-injection property are of pivotal importance in the future development of organic optoelectronic devices. Electron-acceptor molecules with high electron affinity (EA) are widely used in electronic applications, such as hole injection and p-doping. Although p-doping has generally been studied in terms of matching the ionization energy (IE) of organic semiconductors with the EA of acceptor molecules, little is known about the effect of the EA of acceptor molecules on the hole-injection property. In this work, the hole-injection mechanism in devices is completely clarified, and a strategy to optimize the hole-injection property of the acceptor molecule is developed. Efficient and stable hole injection is found to be possible even into materials with IEs as high as 5.8 eV by controlling the charged state of an acceptor molecule with an EA of about 5.0 eV. This excellent hole-injection property enables direct hole injection into an emitting layer, realizing a pure blue organic light-emitting diode with an extraordinarily low turn-on voltage of 2.67 V, a power efficiency of 29 lm W^-1 , an external quantum efficiency of 28% and a Commission Internationale de l'Eclairage y coordinate of less than 0.10.