Organic Electronics

Spectrally independent and wide-angle light extraction of organic light emitting diodes with randomly disassembled nanostructure

Although significant progress in enhancing the internal quantum efficiency (IQE) of OLEDs, achieving an external quantum efficiency that matches their full potential has proven challenging due to optical losses. This paper explores the utilization of Randomly Disassembled Nanostructures (RaDiNa) for light extraction in flexible OLEDs. The study confirms that the implementation of RaDiNa enhances light extraction efficiency, particularly at angles above the critical angle, leading to an increased external quantum efficiency (EQE). The application of a cured polydimethylsiloxane (PDMS) onto the substrate resulted in the RaDiNa-structured OLEDs demonstrating not only an extended viewing angle but also stable light emission across all angles, reinforcing the technology’s value for high-quality display applications. These findings underscore RaDiNa’s potential for significantly improving the efficiency of flexible OLEDs without altering the light emission spectrum based on the viewing angle.

Randomly Disassembled Nanostructure for Wide Angle Light Extraction of Top-Emitting Quantum Dot Light-Emitting Diodes

This paper demonstrates a novel light extraction structure called the randomly disassembled nanostructure (RaDiNa). The RaDiNa is formed by detaching polydimethylsiloxane (PDMS) film from a ZnO nanorod (ZnO NR) layer and laying it on top of the TEQLED. The RaDiNa-attached TE-QLED shows significantly widened angular dependent electroluminescence (EL) intensities over the pristine TE-QLED, confirming the effective light extraction capability of the RaDiNa layer. Consequently, the optimized RaDiNa-attached TE-QLED achieves enhanced external quantum efficiency (EQE) over the reference device by 60%. For systematic analyses, current–voltage–luminance (J–V–L) characteristics are investigated using scanning electron microscopy (SEM) and optical simulation based on COMSOL Multiphysics.

Liq interlayer as electron extraction for PSCs

We introduce a unique transporting layer system that adopts 8-hydroxyquinolinolato-lithium (Liq) as a buffer layer at the interface between [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) and Ag electrode. By introducing the Liq, we effectively decreased the potential energy barrier and iodide accumulation at the interface between PC70BM and Ag electrode, which resulted in an efficient and stable PSC.

ZnO nanorods for electron extraction layer in OSCs

A facile method was introduced and demonstrated to synthesize zinc oxide (ZnO) nanorods (NRs) as an electron transporting layer (ETL) for organic solar cells (OSCs). Hydrothermal synthesis of the NRs showed a constant growth rate of 5.5 nm min−1 from germination to sub-micrometer length. As an ETL of the OSCs, ZnO NRs enhance the charge extraction from the active layer due to their increased interfacial surface area.

Variants of AFM for analysis on decrystallization of PSCs

The origin of the increased efficiency of perovskite solar cells by controlling environmental humidity was investigated using conductive atomic force microscopy (C-AFM) and friction force microscopy (FFM). The perovskite thin films fabricated in a humidity-free environment exhibited better crystallinity and a lower number of trap sites than the films fabricated in a high-humidity environment. Through in-depth analysis using C-AFM and FFM, we found that there was a locally decrystallized area in the perovskite structure fabricated in a high-humidity environment.

Dual-scale AgNWs electrode for flexible OLEDs

We present a transparent electrode based on a dual-scale silver nanowire (AgNW) percolation network embedded in a flexible substrate to demonstrate a significant enhancement in the effective electrical area by filling the large percolative voids present in a long/thick AgNW network with short/thin AgNWs. As a proof of concept, the performance enhancement of a flexible phosphorescent OLED is demonstrated with the dual-scale AgNW percolation network compared to the previous mono-scale AgNWs.

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