Micro-organic Light-emitting Devices Fabricated by Room-temperature Curing Nanoimprint Lithography Using Diamond Molds

2012 ◽  
Vol 1395 ◽  
Author(s):  
Ippei Ishikawa ◽  
Taisuke Okuno ◽  
Shuji Kiyohara ◽  
Yoshio Taguchi ◽  
Yoshinari Sugiyama ◽  
...  
Keyword(s):  
Nanoimprint Lithography ◽  
Room Temperature ◽  
Hole Transport ◽  
Transport Layer ◽  
Electron Transport Layer ◽  
Insulating Layer ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Organic Light ◽  
Organic Light Emitting Devices

ABSTRACTOrganic light-emitting devices (OLEDs) have attracted a lot of attention as a next generation display. In this study, we fabricated the micro-OLEDs by room-temperature curing nanoimprint lithography (RTC-NIL) using diamond molds. The diamond has superior durability and was used as mold material for RTC-NIL. The diamond molds have been fabricated by electron cyclotron resonance (ECR) oxygen ion shower with polysiloxane oxide mask in the electron beam (EB) lithography technology. We fabricated the diamond mold pattern with 10 μm-square dot. The diamond molds have been used to form an insulating layer in micro-OLEDs. The optimum thickness of N,N’-Diphenyl-N,N’-di(m-tolyl)benzidine (TPD) [hole transport layer],Tris(8-quinolinolato)aluminum (Alq3) [electron transport layer] and aluminum (Al) [cathode] were 40 nm, 40 nm and 200 nm, respectively. We succeeded in formation of insulating layer in micro-OLEDs and operation of micro-OLEDs with 10 μm-square-dot by RTC-NIL using diamond molds.

Fabrication of Micro-OLEDs by Room-temperature Curing Nanocontact-print Lithography Using DLC Molds

2012 ◽  
Vol 1511 ◽  
Author(s):  
Ippei Ishikawa ◽  
Keisuke Sakurai ◽  
Shuji Kiyohara ◽  
Taisuke Okuno ◽  
Hideto Tanoue ◽  
...  
Keyword(s):  
Indium Tin Oxide ◽  
Nanoimprint Lithography ◽  
Room Temperature ◽  
Hole Transport ◽  
Transport Layer ◽  
Electron Transport Layer ◽  
Insulating Layer ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Ito Glass

ABSTRACTThe microfabrication technologiesfor organic light-emitting devices (OLEDs) are essential to the fabrication of the next generation of light-emitting devices. The micro-OLEDs fabricated by room-temperature curing nanoimprint lithography (RTC-NIL) using diamond molds have been investigated. However, light emissions from 10 μm-square-dot OLEDs fabricated by the RTC-NIL method have not been uniform. Therefore, we proposed the fabrication of micro-OLEDs by room-temperature curing nanocontact-print lithography (RTC-NCL) using the diamond-like carbon (DLC) mold. The DLC molds used in RTC-NCL were fabricated by an electron cyclotron resonance (ECR) oxygen ion shower with polysiloxane oxide mask in electron beam (EB) lithography technology. The mold patterns are square and rectangle dots which has 10 µm-width, 10 µm-width and50 µm-length, respectively. The height of the patterns is 500 nm. The DLC molds were used to form the insulating layer of polysiloxane in RTC-NCL. We carried out the RTC-NCL process using the DLC mold under the following optimum conditions: 0.1 MPa-pressure for coating DLC mold with polysiloxane film, 2.1 MPa-pressure for transferring polysiloxane from DLC mold pattern to indium tin oxide (ITO) glass substrate. We deposited N, N'-Diphenyl -N, N'-di (m-tolyl)benzidine (TPD) [40 nm-thickness] as hole transport layer / Tris(8-quinolinolato)aluminum (Alq3) [40 nm-thickness] as electron transport layer / Al [200 nm-thickness] as cathode on ITO glass substrateas anode in this order. We succeeded in formation of the insulating layer with square and rectangle dots which has 10 µm-width,10 µm-width and 50 µm-length, and operation of micro-OLEDs by RTC-NIL using DLC molds.

scholarly journals Sub–turn-on exciton quenching due to molecular orientation and polarization in organic light-emitting devices

2020 ◽  
Vol 6 (32) ◽  
pp. eabb2659
Author(s):  
John S. Bangsund ◽  
Jack R. Van Sambeek ◽  
Nolan M. Concannon ◽  
Russell J. Holmes
Keyword(s):  
Transport Layer ◽  
Electron Transport Layer ◽  
Intrinsic Polarization ◽  
Light Emitting ◽  
Light Emitting Devices ◽  
Turn On ◽  
Organic Light ◽  
Organic Light Emitting Devices ◽  
Lock In ◽  
Selection Of

The efficiency of organic light-emitting devices (OLEDs) is often limited by roll-off, where efficiency decreases with increasing bias. In most OLEDs, roll-off primarily occurs due to exciton quenching, which is commonly assumed to be active only above device turn-on. Below turn-on, exciton and charge carrier densities are often presumed to be too small to cause quenching. Using lock-in detection of photoluminescence, we find that this assumption is not generally valid; luminescence can be quenched by >20% at biases below turn-on. We show that this low-bias quenching is due to hole accumulation induced by intrinsic polarization of the electron transport layer (ETL). Further, we demonstrate that selection of nonpolar ETLs or heating during deposition minimizes these losses, leading to efficiency enhancements of >15%. These results reveal design rules to optimize efficiency, clarify how ultrastable glasses improve OLED performance, and demonstrate the importance of quantifying exciton quenching at low bias.

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