This application claims priority from Korean Patent Application No. 10-2011-0132130, filed on Dec. 9, 2011 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field
Apparatuses and methods consistent with exemplary embodiments relate to quantum dot devices including different kinds of quantum dot layers.
2. Description of the Related Art
Recently, interest in various electronic devices using a quantum dot is rising.
The quantum dot is a semiconductor material having a nanocrystal structure having a diameter of less than about 10 nanometers, and takes a quantum confinement effect. The quantum dot is formed more than hundreds of thousands of electrons. However, most of the electrons are strongly bound to an atomic nucleus, and thus, the number of free electrons that are not bounded to the atomic nucleus is limited in the range of about one to about a hundred. In this case, an electrons' energy level is discontinuously limited, and thus, the quantum dot shows electrical and optical characteristics different from those of a semiconductor in a bulk state forming a continuous energy band. Since the energy level of the quantum dot varies depending on the size thereof, it is possible to adjust the bandgap of the quantum dot by simply changing the size thereof. For example, in a case where the quantum dot is used in a light emitting device, an emission wavelength may be adjusted by only changing its size.
Thus, the quantum dot may be widely used in light emitting devices, solar cells, transistors, and display devices according to the above characteristics.
Aspects of one or more exemplary embodiments provide quantum dot devices in which the movement of electrons is controllable and which has high efficiency.
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 exemplary embodiments.
According to an aspect of an exemplary embodiment, a quantum dot device includes: a cathode layer; an anode layer; an active layer that is disposed between the cathode layer and the anode layer and comprises a quantum layer; and an electron movement control layer that is disposed between the cathode layer and the anode layer and comprises a different kind of quantum layer having an energy level different from that of the quantum layer comprised in the active layer.
The size of quantum dots of the electron movement control layer may be different from that of quantum dots of the active layer.
The electron movement control layer may include a material different from that of the active layer.
The electron movement control layer may be disposed between the active layer and the cathode layer.
The electron movement control layer may be disposed between the active layer and the anode layer or may be embedded in the active layer.
The electron movement control layer may include a single layer.
The electron movement control layer may include a plurality of layers.
The plurality of layers may be disposed adjacent to each other or may be disposed apart from each other with the active layer therebetween.
At least one of the plurality of layers may be embedded in the active layer.
The different kind of quantum layer included in the electron movement control layer may include: a first different kind of quantum dot layer having an energy level different from that of the active layer; and a second different kind of quantum dot layer having an energy level different from those of the active layer and the first different kind of quantum dot layer.
The size of quantum dots of the first different kind of quantum dot layer or the size of quantum dots of the second different kind of quantum dot layer may be different from that of quantum dots of the active layer.
The first different kind of quantum dot layer or the second different kind of quantum dot layer may include a material different from that of the active layer.
The first different kind of quantum dot layer and the second different kind of quantum dot layer may be disposed adjacent to each other.
The first different kind of quantum dot layer and the second different kind of quantum dot layer may be disposed apart from each other with the active layer therebetwen.
The at least one of the first different kind of quantum dot layer and the second different kind of quantum dot layer may be embedded in the active layer.
An electron transport layer may be further disposed between the cathode layer and the active layer, and a hole transport layer may be further disposed between the anode layer and the active layer.
An electron injection layer may be further disposed between the cathode layer and the electron transport layer, and a hole injection layer may be further disposed between the anode layer and the hole transport layer.
These and/or other aspects will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. In the drawings, like reference numerals refer to like elements throughout and sizes of the respective elements may be exaggerated for clarity and convenience. In this regard, the present exemplary embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, exemplary embodiments are merely described below, by referring to the figures, to explain aspects of the present description.
Referring to
A detailed configuration and material of the quantum dot device 1 according to one or more exemplary embodiments are described below.
The quantum dots of the active layer 150 may include at least one selected from the group consisting of a Si nanocrystal, a II-VI group compound semiconductor nanocrystal, a III-V group compound semiconductor nanocrystal, a IV-VI group compound semiconductor nanocrystal, and any combinations thereof. The II-VI group compound semiconductor nanocrystal may be any at least one selected from the group consisting of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HggZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, and HgZnSTe. The III-V group compound semiconductor nanocrystal may be any at least one selected from the group consisting of GaN, GaP, GaAs, AlN, AlP, AlAs, InN, InP, InAs, GaNP, GaNAs, GaPAs, AlNP, AlNAs, AlPAs, InNP, InNAs, InPAs, GaAlNP, GaAlNAs, GaAlPAs, GaInNP, GaInNAs, GaInPAs, InAlNP, InAlNAs, and InAlPAs. The IV-VI group compound semiconductor nanocrystal may be SbTe.
The quantum dots of the active layer 150 may be enveloped in a sealing element (not shown) in a state in which the quantum dots are dispersed naturally in a dispersion medium such as an organic solvent or a macromolecular resin. Any transparent medium that is not changed in quality by light or does not reflect light while not having an influence on an emission wavelength band of the quantum dots and does not cause a light absorption may be used as the dispersion medium.
For example, the organic solvent may include at least one selected from the group consisting of toluene, chloroform, and ethanol, and the macromolecular resin may include at least one selected from the group consisting of epoxy, silicone, polysthylene, and acrylate. When the macromolecular resin is used as the dispersion medium, a macromolecular resin in which quantum dots are dispersed may be injected into a sealing element and then be hardened.
A light emission of the active layer 150 including the quantum dot layer occurs when excited electrons transit from a conduction band to a valence band, and shows characteristics in which an emission wavelength varies depending on the size of the quantum dots even though the quantum dots are formed, for example, of the same material. Since a light having a shorter wavelength is emitted as the size of the quantum dots becomes smaller, it is possible to obtain a light in a desired wavelength range by adjusting the size of the quantum dots. The size of the quantum dots is adjustable by properly changing a growth condition of a nanocrystal thereof.
The electron movement control layer 130 includes a different kind of quantum dot layer to have an energy level different from that of the quantum dot layer of the active layer 150. An energy level difference between the electron movement control layer 130 and the active layer 150 may be determined to the extent in which an electron mobility characteristic of the quantum dot device 1 may be adjusted within the range in which the emission wavelength band of the active layer 150 is maintained. The electron movement control layer 130 may include quantum dots having a size different from that of the quantum dots of the active layer 150, may include quantum dots including a material different from that of the quantum dots of the active layer 150, or may include quantum dots having a size and a material different from those of the quantum dots of the active layer 150.
The cathode layer 190 and the anode layer 110 may include an electrode material, and, for example, may include indium tin oxide (ITO) or indium zinc oxide (IZO) as a transparent electrode material. In addition, at least one of the cathode layer 190 and the anode layer 110 may include a reflective metal material to radiate a light generated in the active layer 150 in a predetermined direction, for example, only in the up direction or down direction of the quantum dot device 1. For example, Al, Cu, or the like may be used as the reflective metal material.
Although a case in which the electron movement control layer 130 is disposed between the active layer 130 and the anode layer 110 is illustrated in
In the quantum dot device 2 of the present exemplary embodiment, an electron movement control layer 130 is disposed between a cathode layer 190 and an active layer 150 differently from the quantum dot device 1 of
In the quantum dot device 3 of the present exemplary embodiment, an electron movement control layer 130 is embedded in an active layer 150 differently from the quantum dot device 1 of
Related art devices using a quantum dot use a material such as a semiconductor polymer, an organic macromolecule, a ceramic, or the like to control and improve electron mobility and hole mobility, whereas the quantum dot devices according to exemplary embodiments described above use a quantum dot having an energy level different from that of the active layer 150. Since the size of the quantum dot and a material of the quantum dot may be easily adjusted, the electron mobility may be controlled in various ranges, and thus, the efficiency of the quantum dot device may be improved.
The quantum dot layer illustrated in
In addition, it has been experimentally confirmed that the electron mobility varies according to a configuration of quantum dots of the electron movement control layer 130 in a structure as the quantum dot device 1 of
Below, with reference to
In a quantum dot device 4 of
In the quantum dot device 5 of
A quantum dot device 6 of
In a quantum dot device 8 of
The size of quantum dots of the first different kind of quantum dot layer 141 is different from that of quantum dots of the active layer 150. Although a case in which the size of quantum dots of the first different kind of quantum dot layer 141 is larger than that of quantum dots of the active layer 150 is illustrated in
As illustrated in
In the quantum dot device 9 of
In a quantum dot device 10 of
In a quantum dot device 11 of
The electron transport layer 188 may include at least one of various material capable of transmitting electrons to the active layer 150. For example, the electron transport layer 188 may include a metal oxide such as TiO2, ZrO2, or HfO2, or an inorganic substance including Si3N4. In addition, the electron transport layer 188 may include an N-type semiconductor material, for example, n-AlxGayInzN (x+y+z=1) or the like. Although a case in which the electron transport layer 188 is a single layer is illustrated in
The hole transport layer 128 may include at least one of various material capable of transmitting holes to the active layer 150. For example, the hole transport layer 128 may include a conductive macromolecule material such as PEDOT, PSS, PPV, PVK, or the like. In addition, the hole transport layer 128 may include a P-type semiconductor material, for example, p-AlxGayInzN (x+y+z=1) or the like. Although a case in which the hole transport layer 128 is a single layer is illustrated in
Although a case in which the electron transport layer 188 and the hole transport layer 128 are added to the quantum dot device 1 of
In a quantum dot device 12 of
In the quantum dot devices described above, by introducing a different kind of quantum dot layer having an energy level different from that of a quantum dot layer of an active layer, electrical characteristics such as electron mobility may be adjusted, and a high efficiency may be obtained.
In addition, by adjusting at least one of a material, a size, and a disposition of quantum dots of the different quantum dot layer, an electron movement speed or dispersion of electrons in the quantum dot devices may be controlled.
The above-described exemplary embodiments exemplify a case in which an electron movement control layer including quantum dots having an energy level different from that of quantum dots of an active layer is adopted in a quantum dot device applied as a light emitting device. However, the electron movement control layer according to exemplary embodiments may be widely adopted in other devices, such as solar cells, transistors, and display devices, which use quantum dots.
While exemplary embodiments have been particularly shown and described above, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present inventive concept as defined by the following claims.
Number | Date | Country | Kind |
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10-2011-0132130 | Dec 2011 | KR | national |