Effects of mixed host spatial distribution on the efficiency of blue phosphorescent organic light-emitting diodes

Lee, Sang‐Min; Tang, Ching Wan; Rothberg, Lewis J.

doi:10.1063/1.4739499

Cited by 12 publications

(6 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[27] The different charge mobilitis of the host may mainly affect the location and width of the recombination zone, governing the behaviors of charge injection and transport in the EML. [28,29]…”

Section: Resultsmentioning

confidence: 99%

Effects of Charge Transport Materials on Blue Fluorescent Organic Light-Emitting Diodes with a Host-Dopant System

et al. 2019

View full text Add to dashboard Cite

High efficiency blue fluorescent organic light-emitting diodes (OLEDs), based on 1,3-bis(carbazol-9-yl)benzene (mCP) doped with 4,4’-bis(9-ethyl-3-carbazovinylene)-1,1’-biphenyl (BCzVBi), were fabricated using four different hole transport layers (HTLs) and two different electron transport layers (ETLs). Fixing the electron transport material TPBi, four hole transport materials, including 1,1-Bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), N,N’-Di(1-naphthyl)-N,N’-diphenyl-(1,1’-biphenyl)-4’-diamine(NPB), 4,4’-Bis(N-carbazolyl)-1,1,-biphenyl (CBP) and molybdenum trioxide (MoO3), were selected to be HTLs, and the blue OLED with TAPC HTL exhibited a maximum luminance of 2955 cd/m2 and current efficiency (CE) of 5.75 cd/A at 50 mA/cm2, which are 68% and 62% higher, respectively, than those of the minimum values found in the device with MoO3 HTL. Fixing the hole transport material TAPC, the replacement of TPBi ETL with Bphen ETL can further improve the performance of the device, in which the maximum luminance can reach 3640 cd/m2 at 50 mA/cm2, which is 23% higher than that of the TPBi device. Furthermore, the lifetime of the device is also optimized by the change of ETL. These results indicate that the carrier mobility of transport materials and energy level alignment of different functional layers play important roles in the performance of the blue OLEDs. The findings suggest that selecting well-matched electron and hole transport materials is essential and beneficial for the device engineering of high-efficiency blue OLEDs.

show abstract

Section: Resultsmentioning

confidence: 99%

Effects of Charge Transport Materials on Blue Fluorescent Organic Light-Emitting Diodes with a Host-Dopant System

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Considering no chemical doping was used for the ETL of the current devices, there might be still some further room to reduce the driving voltage by using chemically doping technology . In addition, the driving voltage may also be further reduced by utilizing double host materials or double EMLs[1c],[5b] to tune the carrier injection barrier between the EML and the carrier transport layer. These low operating voltage devices makes them very interesting for high power‐efficiency applications such as in mobile devices and organic lighting.…”

Section: Discussionmentioning

confidence: 99%

Pyridine‐Containing Electron‐Transport Materials for Highly Efficient Blue Phosphorescent OLEDs with Ultralow Operating Voltage and Reduced Efficiency Roll‐Off

Chen

Liu

et al. 2014

Adv Funct Materials

133

View full text Add to dashboard Cite

3268www.MaterialsViews.com wileyonlinelibrary.com reached 90 lm W −1 at 1000 cd m −2 , [ 2 ] which is readily above the effi ciency of a general fl uorescent tube. However, there is still a big room for improvement compared to the theoretical limit of 248 lm W −1 . [ 3 ] Among the three primary colors, effi cient blue light emission is the bottleneck for effi cient full-color OLED display and white OLEDs. [ 4 ] In the past few years, many studies have focused on improving external quantum effi ciency ( h ext ) of blue OLEDs by utilizing a common blue phosphorescent emitter of iridium(III) bis [(4,6-h ext values over 20% have been achieved by developing new materials, such as bipolar host materials and electron-transport materials (ETMs) with high triplet energy level, due to effi cient harvesting of both electro-generated singlet and triplet excitons for phosphorescent emission from OLEDs. [ 1c , 5 ] Most recently, h ext values were further improved to ≈30% by Lee et al. by using a pyrido [2,3-b ] indole derivative as the host material and a 50-nm-ITO-coated glass as the substrate due to the improved carrier balance and light outcoupling. [ 6 ] Aside from the external quantum effi ciency, reducing operating voltage is also crucially important for high power conversion effi ciency. As the most recent report, although h ext value of ≈30% has been achieved, the power effi ciency was compromised by the relatively high driving voltage, giving the maximum power effi ciency ( h P ) of only 50.6 lm W −1 . [ 6b ] Nevertheless, unlike the most intensively investigated EQE, reducing operating voltage without compromising external quantum effi ciency seems to be ignored or underestimated. The limit of operating voltage is generally believed to be equal to the energy band gap ( E g ) of the emitter molecule or the photon energy ( hv ) of the emission light divided by the electron charge ( e ), which is corresponding to the energy difference between the highest occupied molecular orbital (HOMO) and the unoccupied molecular orbital (LUMO). Although a few exceptions were reported, where the devices could even be operated at half of the voltage of E g / e , [ 7 ] the electroluminescence was achieved with an Augerassisted mechanism, and multiple electrons should be used for one photon emission to give a very low h ext of 0.4%.

show abstract

“…The simplest OLED structure consists only a single emissive layer (EML) sandwiched between two electrodes, Anode and Cathode. In order to enhance the electro luminescence efficiency, several methods have been proposed [3]- [11]. The application of hole transport layer (HTL) as well as electron transport layer (ETL) between the electrodes and the EML is considered as the easiest way to enhance the electroluminescence efficiency.…”

Section: Introductionmentioning

confidence: 99%

Effect of Hole Transport Layer and Electron Transport Layer on the performance of a single emissive layer Organic Light Emitting Diode

Udhiarto

Sister

Rini

et al. 2015

2015 International Conference on Quality in Research (QiR)

View full text Add to dashboard Cite

Ahstract-In this paper we study the effect of Hole Transport Layer NPB (N,N'-diphenyl-N,N'-his(l-naphtyl)-J,J '-hiphenyl-4,4" diamine) and Electron Transport Layer on the performance of a single layer of Blue Organic Light Emitting Diode. Three different structures are analyzed and are compared to the reference structure. SimOLED is used to simulate and to analyze both electrical and optical characteristics. We found that the addition of 1 nm hole transport layer significantly improve the luminance by more than 1.5 times which is ascribed to the increase of the hole injection leading to the balance charge in the emissive layer. On the other hand, the application of 1 nm electron transport layer provide lower operating voltage which become more significant when both hole transport layer and electron transport layer are combined. The proposed structure reaches a luminance of 49,543 cd/m 2 at 10 V.

show abstract

Effects of mixed host spatial distribution on the efficiency of blue phosphorescent organic light-emitting diodes

Cited by 12 publications

References 14 publications

Effects of Charge Transport Materials on Blue Fluorescent Organic Light-Emitting Diodes with a Host-Dopant System

Effects of Charge Transport Materials on Blue Fluorescent Organic Light-Emitting Diodes with a Host-Dopant System

Pyridine‐Containing Electron‐Transport Materials for Highly Efficient Blue Phosphorescent OLEDs with Ultralow Operating Voltage and Reduced Efficiency Roll‐Off

Effect of Hole Transport Layer and Electron Transport Layer on the performance of a single emissive layer Organic Light Emitting Diode

Contact Info

Product

Resources

About