Releasing the Trapped Light for Efficient Silver Nanowires‐Based White Flexible Organic Light‐Emitting Diodes

Abstract

be taken into account. One important consideration involves replacing the conventional indium-tin-oxide (ITO) due to its naturally brittle nature. [7][8][9][10][11] Therefore, it is imperative to develop flexible transparent electrodes (FTEs) with high optical transparency, high electrical conductivity, good mechanical flexibility, and high processing compatibility with plastic substrates. [6][7][8] In recent years, several kinds of FTEs have been proposed as an ITO alternative, such as carbon-based conductive materials (e.g., graphene, carbon nanotubes), [6,12,13] conductive polymers, [14] metal grids, [9,15] or metal nanowires. [16][17][18][19] Among these materials, silver nanowires (AgNWs) have become one of the most promising candidates for FTEs, [18,19] since they exhibit not only excellent optical and electrical properties but also high chemical and mechanical stability. Particularly, AgNWsbased FTEs can be fabricated through low-temperature solution processing (e.g., spin coating, drop casting, bar coating, or spray coating), which is somewhat compatible with plastic substrates. [7,[18][19][20][21] However, high roughness arising from the junctions and aggregation of randomly distributed AgNWs can cause high leakage currents and even short circuits in flexible OLEDs, which apparently hinders the extensive applications of AgNWs-based FTEs in lightemitting applications. [22] To circumvent this problem, a wide variety of solutions (e.g., thermal annealing, plasma welding, mechanical pressing, chemical modification, or embedment in polymers) have been reported to relieve roughness-induced device failures. [23][24][25][26] Although these techniques can, to some extent, planarize the surface of AgNWs-based FTEs, such additional procedures can complicate the fabrication process and are incompatible with scalable solution processability.In addition to the mechanical flexibility of novel FTEs, another aspect to consider for flexible OLEDs is how to achieve the highest possible efficiency in minimizing power consumption for flexible displays used in highly portable or wearable applications. Indeed, the development of excellent light-emitting materials and efficient device structures has led to an internal quantum efficiency approaching 100% with negligible loss during the electron-to-photon conversion. [1][2][3][4] Nevertheless, a majority of the internally generated light in a conventional Flexible organic light-emitting diodes (OLEDs) are attracting tremendous attention due to their promise as a key element in bendable display and curved lighting applications. However, their performance in terms of efficiency and bendability is limited, since flexible transparent electrodes with superior electrical, optical, and mechanical properties are rare. Here, a multifunctional electrode architecture that is based on flexible plastic, and consists of electrically conductive silver nanowires, a nanopatterned ZnO outcoupling layer, and a hole-injection polymer layer, is proposed for the actualization of high-performance flexi...

Rational Interface Engineering for Efficient Flexible Perovskite Light-Emitting Diodes

“…Upon optimization of the perovskite emitter through interface-stimulated crystallization and passivation, the full potential of PeLEDs on flexible plastic was further exploited by replacing the brittle ITO with an alternate FTE. Among several kinds of widely developed FTEs ( e.g ., graphene, metallic nanostructures, metal/dielectric multilayer), − AgNWs are a promising candidate due to their form-factor advantages such as superior mechanical flexibility, electrical conductivity, optical transparency, chemical stability, and scalable solution processability. − Particularly, combining AgNWs with a light outcoupling scheme holds a great potential for achieving highly efficient flexible PeLEDs on plastic substrates, which altogether eliminates the use of ITO and allows the outcoupling enhancement for the waveguided light. , Here, a composite electrode architecture consisting of randomly distributed AgNWs and sol–gel-derived zinc oxide (ZnO) film (AgNWs/ZnO) is built as a FTE in PeLEDs on flexible plastic. Figure a illustrates the schematic of the flexible PeLED device structure constructed with a nanopatterned AgNWs/ZnO FTE on a polyethylene terephthalate (PET) substrate.…”

Dopant-Tunable Ultrathin Transparent Conductive Oxides for Efficient Energy Conversion Devices

“…the required minimum FOM value [35]. Figure 2g shows the transmittance (at 550 nm) versus R SH of the 30-and 50-nm Ni-ITO (solid star symbols) in comparison with those of the various types of transparent electrodes reported in the literature [6][7][8][9][36][37][38][39][40]. All m-TCOs (ITO, AZO, FTO) studied here yielded FOM values ranging from 79 to 194 (Fig.…”

“…Modern energy conversion devices, including organic/inorganic solar cells [1] and light-emitting diodes [2], require innovative thin transparent electrodes with high electrical conductivity and optical transparency. To satisfy the growing demand for advanced transparent electrodes, transparent conductive oxides (TCOs) such as indium tin oxide (ITO) [3], aluminum-doped ZnO (AZO) [4], and fluorine-doped SnO (FTO) [5] have been developed, along with various types of transparent electrodes such as metal nanomesh [6], metal nanowire [7], conductive polymer [8], and graphene [9] over the past several decades. However, most conventional TCOs are n-type owing to localized oxygen, which impedes band alignment and charge balance when they are used as p-electrodes of such devices [10], thereby resulting in low quantum efficiency.…”

Light extraction from organic light emitting diodes (OLEDs)

“…Development of efficient water and oxygen barrier films will advance the use of plastic substrates. Examples of studied various plastic substrates for different applications include polyethersulfone (PES) [135], polycarbonate (PC) [116,136], polyethylene terephthalate (PET) [116,[137][138][139][140][141], polyimide (PI) [55,[142][143][144][145]) (colorless PI, n = 1.63), and the n = 1.56 Norland optical adhesive NOA63 [146].…”