26‐2: Extremely High‐Efficient OLED Achieving External Quantum Efficiency over 40% by Carrier Injection Layer with Super‐Low Refractive Index

Watabe, Takeyoshi; Yamaoka, Ryohei; Ohsawa, Nobuharu; Tomida, Airi; Seo, Satoshi; Yamazaki, Shunpei

doi:10.1002/sdtp.12554

Cited by 9 publications

(4 citation statements)

References 29 publications

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“…Combining the fact that the PL lifetimes of the MAPbBr 3 film and the MAPbBr 3 /Bphen film are nearly identical (see Figure S5, Supporting Information), it is possible that the Bphen layer only affects the light out‐coupling of perovskites rather than the carrier dynamics. Since PTAA shares a similar refractive index (≈1.7) as Bphen, [ 24,25 ] similar light out‐coupling effects that reduce the gain property (SE intensity) can be expected. Thus, the light out‐coupling effect of the transport layers is also excluded to explain the simultaneously enhanced ASE emission and suppressed spontaneous emission after combining an additional PTAA layer.…”

Section: Resultsmentioning

confidence: 99%

Transport Layer Engineering Toward Lower Threshold for Perovskite Lasers

et al. 2023

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Charge-transport layers are essential for achieving electrically pumped perovskite lasers. However, their role in perovskite lasing is not fully understood. Here, the role of charge-transport layers on the lasing actions of perovskite films is explored by investigating the amplified spontaneous emission (ASE) thresholds. A largely reduced ASE threshold and enhanced ASE intensity is demonstrated by introducing an additional hole transport layer poly(triaryl amine) (PTAA). It is shown that the key role of the PTAA layer is to accelerate the hot-carrier cooling process by extracting holes in perovskites. With reduced hot holes, the Auger recombination loss is largely suppressed, resulting in decreased ASE threshold. This argument is further supported by the fact that the ASE threshold can be further reduced from 25.7 to 7.2 μJ cm −2 upon switching the pumping wavelength from 400 to 500 nm to directly avoid excess hot-hole generation. This work exemplifies how to further reduce the ASE threshold with transport layer engineering through hot-hole manipulation. This is critical to maintaining the excellent gain properties of perovskites when integrating them into electrical devices, paving the way for electrically pumped perovskite lasers.

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Section: Resultsmentioning

confidence: 99%

Transport Layer Engineering Toward Lower Threshold for Perovskite Lasers

et al. 2023

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“…In the work reported by Watabe et al,68 a remarkably high EQE of 41.0% was demonstrated in a bottom‐emission PhOLED by combining HIL and EIL, both of which exhibit super low refractive indices. This is in a strong contrast with the fact that a reference control device containing conventional HIL and EIL yielded an EQE of 30.5%.…”

Section: Toward the Ultimate Limit Of The Optical Efficiency In Oledsmentioning

confidence: 88%

Organic Light‐Emitting Diodes: Pushing Toward the Limits and Beyond

et al. 2020

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Organic light‐emitting diodes (OLEDs) are established as a mainstream light source for display applications and can now be found in a plethora of consumer electronic devices used daily. This success can be attributed to the rich luminescent properties of organic materials, but efficiency enhancement made over the last few decades has also played a significant role in making OLEDs a practically viable technology. This report summarizes the efforts made so far to improve the external quantum efficiency (EQE) of OLEDs and discusses what should further be done to push toward the ultimate efficiency that can be offered by OLEDs. The study indicates that EQE close to 58% and 80% can be within reach without and with additional light extraction structures, respectively, with an optimal combination of cavity engineering, low‐index transport layers, and horizontal dipole orientation. In addition, recent endeavors to identify possible applications of OLEDs beyond displays are presented with emphasis on their potential in wearable healthcare, such as OLED‐based pulse oximetry as well as phototherapeutic applications based on body‐attachable flexible OLED patches. OLEDs with fabric‐like form factors and washable encapsulation strategies are also introduced as technologies essential to the success of OLED‐based wearable electronics.

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“…They showed that they could reduce the RI of the tris(8-hydroxyquinoline)aluminum (Alq 3 )-based ETL from 1.75 to 1.45, and consequently increase the outcoupling by 30%. Independently, Watabe et al [57] developed hole and electron injection layer (HIL and EIL, respectively) materials, based on blends of a metal oxide such as MoO x and an organic compound, with RIs <1.6 and <1.5, respectively. As a result, their OLED EQEs increased from 30% to 41%.…”

Section: Manipulating the Refractive Index Of The Organic Layersmentioning

confidence: 99%

Light extraction from organic light emitting diodes (OLEDs)

Shinar

2022

J. Phys. Photonics

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OLED technology continues to make strides, particularly in display technology with costs decreasing and consumer demand growing. Advances are also seen in OLED solid state lighting (SSL), though broad utilization of this technology is lagging. This situation has prompted extensive R&D to achieve high efficiency SSL devices at cost-effective fabrication. Here we review advances and challenges in enhancing forward light outcoupling from OLEDs. Light outcoupling from conventional bottom (through the transparent anode)-emitting OLEDs is typically ~20%, due largely to losses to external, i.e., substrate waveguide modes, internal waveguide modes between the metal cathode and the anode/substrate interface, and surface plasmon-polariton modes at the metal cathode/organic interface. We address these major photon loss paths, presenting various extraction approaches. Some approaches are devoid of light extraction structures; they include replacing the commonly used ITO anode, manipulating the refractive index of the substrate and/or organic layers, and evaluating emitters with preferential horizontal transition dipoles. Other approaches include the use of enhancing structures such as microlens arrays, scattering layers, patterned substrates, as well as substrates with various buried structures that are planarized by high index layers. A maximal external quantum efficiency as high as 78% was reported for white planarized OLEDs with a hemispherical lens to extract the substrate mode. Light outcoupling from OLEDs on flexible substrates is also addressed, as the latter become of increasing interest for foldable displays and decorative lighting, with plastic substrates being evaluated also for biomedical, wearable, and automotive applications.

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26‐2: Extremely High‐Efficient OLED Achieving External Quantum Efficiency over 40% by Carrier Injection Layer with Super‐Low Refractive Index

Cited by 9 publications

References 29 publications

Transport Layer Engineering Toward Lower Threshold for Perovskite Lasers

Transport Layer Engineering Toward Lower Threshold for Perovskite Lasers

Organic Light‐Emitting Diodes: Pushing Toward the Limits and Beyond

Light extraction from organic light emitting diodes (OLEDs)

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