CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Applications Nos. 10-2017-0113561, filed on Sep. 5, 2017 and 10-2018-0105124, filed on Sep. 4, 2018, in the Korean Intellectual Property Office, and all the benefits accruing therefrom under 35 U.S.C. § 119, the content of which is incorporated herein in its entirety by reference.

BACKGROUND

1. Field

The present disclosure relates to an organic light-emitting device.

2. Description of the Related Art

Organic light-emitting devices (OLEDs) are self-emission devices which produce full-color images. In addition, OLEDs have wide viewing angles and exhibit excellent driving voltage and response speed characteristics.

OLEDs include an anode, a cathode, and an organic layer disposed between the anode and the cathode, wherein the organic layer includes an emission layer. A hole transport region may be disposed between the anode and the emission layer, and an electron transport region may be disposed between the emission layer and the cathode. Holes provided from the anode may move toward the emission layer through the hole transport region, and electrons provided from the cathode may move toward the emission layer through the electron transport region. The holes and the electrons recombine in the emission layer to produce excitons. These excitons transit from an excited state to a ground state to thereby generate light.

Various types of organic light emitting devices are known. However, there still remains a need in OLEDs having low driving voltage, high efficiency, high brightness, and long lifespan.

SUMMARY

Provided is an organic light-emitting device satisfying certain parameters, and thus having a long lifespan.

Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments.

According to an aspect of an embodiment, an organic light-emitting device may include

a first electrode;

a second electrode facing the first electrode; and

an emission layer disposed between the first electrode and the second electrode,

wherein

the emission layer may include a host and a dopant,

the emission layer may emit a phosphorescent light,

the dopant may be an organometallic compound,

a photoluminescent quantum yield (PLQY) of the dopant may be about 0.8 or greater and about 1.0 or less,

a decay time of the dopant may be about 0.1 microseconds or greater and about 2.9 microseconds or less,

0.1 electron volts≤HOMO (dopant)−HOMO (host)≤about 0.4 electron volts,

wherein

the HOMO (dopant) represents a highest occupied molecular orbital (HOMO) energy level (expressed in electron volts) of the dopant, and

the HOMO (host) represents, in a case where the host included in the emission layer includes one type of host, a HOMO energy level (expressed in electron volts) of the one type of host; or in a case where the host included in the emission layer is a mixture of two or more different types of host, a highest HOMO energy level from among HOMO energy levels (expressed in electron volts) of the two or more different types of host,

the PLQY of the dopant may be a PLQY of Film 1,

the decay time of the dopant may be calculated from a time-resolved photoluminescence (TRPL) spectrum with respect to Film 1,

Film 1 is a film having a thickness of 40 nanometers obtained by vacuum-deposition of the host and the dopant included in the emission layer in a weight ratio of 90:10 on a quartz substrate at a vacuum degree of 10−7torr.

the HOMO (dopant) may be a negative value measured by using a photoelectron spectrometer in an ambient atmosphere with respect to a film having a thickness of 40 nanometers obtained by vacuum-deposition of 1,4-bis(triphenylsilyl)benzene and the dopant included in the emission layer in a weight ratio of 85:15 on an indium tim oxide (ITO) substrate at a vacuum degree of 10−7torr, and

the HOMO (host) may be, i) in a case where the host includes one type of host, a negative value measured by using a photoelectron spectrometer in an ambient atmosphere with respect to a film having a thickness of 40 nanometers obtained by vacuum-deposition of the one type of host on an ITO substrate at a vacuum degree of 10−7torr; or ii) in a case where the host is a mixture of two or more different types of host, a largest negative value from among negative values measured by using a photoelectron spectrometer in an ambient atmosphere with respect to films having a thickness of 40 nanometers obtained by vacuum-deposition of each of the two or more different types of host on an ITO substrate at a vacuum degree of 10−7torr.

According to an aspect of other embodiment, an organic light-emitting device may include:

a first electrode;

a second electrode facing the first electrode;

emission units in the number of m stacked between the first electrode and the second electrode and comprising at least one emission layer; and

charge generating layers in the number of m−1 disposed between each two adjacent emission units from among the m emission units, the each m−1 charge generating layers comprising an n-type charge generating layer and a p-type charge generating layer,

wherein m is an integer of 2 or greater,

a maximum emission wavelength of light emitted from at least one of the emission units in the number of m differs from that of light emitted from at least one of the other emission units,

the emission layer comprises a host and a dopant,

the emission layer emits a phosphorescent light,

the dopant is an organometallic compound,

a photoluminescence quantum yield (PLQY) of the dopant is about 0.8 or greater and about 1.0 or less,

a decay time of the dopant is about 0.1 microseconds or greater and about 2.9 microseconds or less,

0.1 electron volts≤HOMO (dopant)−HOMO (host)≤about 0.4 electron volts, wherein the HOMO (dopant) represents a highest occupied molecular orbital (HOMO) energy level (expressed in electron volts) of the dopant, and the HOMO (host) represents, in a case where the host comprised in the emission layer comprises one type of host, a HOMO energy level (expressed in electron volts) of the one type of host; or in a case where the host comprised in the emission layer is a mixture of two or more different types of host, a highest HOMO energy level from among HOMO energy levels (expressed in electron volts) of the two or more different types of host,

the PLQY of the dopant is a PLQY of Film 1,

the decay time of the dopant is calculated from a time-resolved photoluminescence (TRPL) spectrum with respect to Film 1,

Film 1 is a film having a thickness of 40 nanometers obtained by vacuum-deposition of the host and the dopant comprised in the emission layer in a weight ratio of 90:10 on a quartz substrate at a vacuum degree of 10−7torr,

the HOMO (dopant) is a negative value measured by using a photoelectron spectrometer in an ambient atmosphere with respect to a film having a thickness of 40 nanometers obtained by vacuum-deposition of 1,4-bis(triphenylsilyl)benzene and the dopant comprised in the emission layer in a weight ratio of 85:15 on an ITO substrate at a vacuum degree of 10−7torr, and

the HOMO (host) is, i) in a case where the host comprises one type of host, a negative value measured by using a photoelectron spectrometer in an ambient atmosphere with respect to a film having a thickness of 40 nanometers obtained by vacuum-deposition of the one type of host on an ITO substrate at a vacuum degree of 10−7torr; or ii) in a case where the host is a mixture of two or more different types of host, a largest negative value from among negative values measured by using a photoelectron spectrometer in an ambient atmosphere with respect to films having a thickness of 40 nanometers obtained by vacuum-deposition of each of the two or more different types of host on an ITO substrate at a vacuum degree of 10−7torr.

According to an aspect of other embodiment, an organic light-emitting device may include:

a first electrode;

a second electrode facing the first electrode; and

emission layers in the number of m stacked between the first electrode and the second electrode,

wherein

m is an integer of 2 or greater,

a maximum emission wavelength of light emitted from at least one of the emission layers in the number of m differs from that of light emitted from at least one of the other emission layers,

the emission layer comprises a host and a dopant,

the emission layer emits a phosphorescent light,

the dopant is an organometallic compound,

a photoluminescence quantum yield (PLQY) of the dopant is about 0.8 or greater and about 1.0 or less,

a decay time of the dopant is about 0.1 microseconds or greater and about 2.9 microseconds or less,

0.1 electron volts≤HOMO (dopant)−HOMO (host)≤about 0.4 electron volts, wherein the HOMO (dopant) represents a highest occupied molecular orbital (HOMO) energy level (expressed in electron volts) of the dopant, and the HOMO (host) represents, in a case where the host comprised in the emission layer comprises one type of host, a HOMO energy level (expressed in electron volts) of the one type of host; or in a case where the host comprised in the emission layer is a mixture of two or more different types of host, a highest HOMO energy level from among HOMO energy levels (expressed in electron volts) of the two or more different types of host,

the PLQY of the dopant is a PLQY of Film 1,

the decay time of the dopant is calculated from a time-resolved photoluminescence (TRPL) spectrum with respect to Film 1,

Film 1 is a film having a thickness of 40 nm obtained by vacuum-deposition of the host and the dopant comprised in the emission layer in a weight ratio of 90:10 on a quartz substrate at a vacuum degree of 10−7torr,

the HOMO (dopant) is a negative value measured by using a photoelectron spectrometer in an ambient atmosphere with respect to a film having a thickness of 40 nanometers obtained by vacuum-deposition of 1,4-bis(triphenylsilyl)benzene and the dopant comprised in the emission layer in a weight ratio of 85:15 on an ITO substrate at a vacuum degree of 10−7torr, and

the HOMO (host) is, i) in a case where the host comprises one type of host, a negative value measured by using a photoelectron spectrometer in an ambient atmosphere with respect to a film having a thickness of 40 nanometers obtained by vacuum-deposition of the one type of host on an ITO substrate at a vacuum degree of 10−7torr; or ii) in a case where the host is a mixture of two or more different types of host, a largest negative value from among negative values measured by using a photoelectron spectrometer in an ambient atmosphere with respect to films having a thickness of 40 nanometers obtained by vacuum-deposition of each of the two or more different types of host on an ITO substrate at a vacuum degree of 10−7torr.

