JP2008251269A - Light-emitting element - Google Patents
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- JP2008251269A JP2008251269A JP2007089116A JP2007089116A JP2008251269A JP 2008251269 A JP2008251269 A JP 2008251269A JP 2007089116 A JP2007089116 A JP 2007089116A JP 2007089116 A JP2007089116 A JP 2007089116A JP 2008251269 A JP2008251269 A JP 2008251269A
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Abstract
Description
本発明は、発光素子に関するものである。特に、ガラスやプラスチック等の安価な基板を用い、大面積化が容易で、かつ直流低電圧で発光するために発光効率が良好で、無機材料で構成されるために耐久性に優れる発光素子に関するものである。 The present invention relates to a light emitting element. In particular, the present invention relates to a light-emitting element that uses an inexpensive substrate such as glass or plastic, is easy to increase in area, has good luminous efficiency because it emits light at a DC low voltage, and has excellent durability because it is composed of an inorganic material. Is.
近年、液晶ディスプレイに代表されるフラットパネルディスプレイの大面積化に対応可能な面光源として、有機ＥＬ、無機ＥＬといったエレクトロルミネッサンス（以下、ＥＬ）を利用した発光体に期待が集まっている。有機ＥＬは、有機発光層を正孔注入層、電子注入層で挟んだ構造をガラス基板もしくはプラスチック基板上に形成し、直流、低電圧を印加する。直流により電子、正孔を注入され、これらが発光層内で再結合して発光する。有機ＥＬ素子は、直流、低電圧で発光するため、５０ｌｍ／Ｗ以上の高効率が得られている。また、大面積化が可能な蒸着法や塗布で有機材料をガラス基板上に製膜すれば発光することから大面積化が容易である。しかし、有機材料であるために寿命が短く、用途が限定されている。 In recent years, as a surface light source that can cope with an increase in area of a flat panel display typified by a liquid crystal display, there is an expectation for a light-emitting body that uses electroluminescence (hereinafter referred to as EL) such as organic EL and inorganic EL. In organic EL, a structure in which an organic light emitting layer is sandwiched between a hole injection layer and an electron injection layer is formed on a glass substrate or a plastic substrate, and a direct current and a low voltage are applied. Electrons and holes are injected by direct current, and these recombine in the light emitting layer to emit light. Since the organic EL element emits light with direct current and low voltage, high efficiency of 50 lm / W or more is obtained. In addition, if an organic material is formed on a glass substrate by a vapor deposition method or coating capable of increasing the area, light emission can be easily achieved. However, since it is an organic material, its lifetime is short and its use is limited.
無機ＥＬは、半導体中に希土類などの発光中心剤を含ませた発光層を絶縁体の層で挟んだ構造を安価なガラス基板上に形成し、交流の高電圧を印加する。高電界下で半導体の電子が高速に加速されて発光中心剤に衝突して基底状態の電子を励起状態にし、励起状態から電子が基底状態に戻るときに発光する。ガラス基板を用い、多結晶の層を形成すれば発光することから大面積化は容易である。しかし数百Vという高い電圧を必要とするために発光効率が非常に低く、大きな電源を必要として簡易性に欠けると言う課題が有る。以上のように、従来の有機ＥＬ，無機ＥＬ素子では、発光効率や輝度、寿命といった点で、発光体としての性能が不十分であった。 Inorganic EL forms a structure in which a light emitting layer containing an emission center agent such as rare earth in a semiconductor is sandwiched between insulating layers on an inexpensive glass substrate, and applies an alternating high voltage. Under high electric field, semiconductor electrons are accelerated at high speed and collide with the emission center agent to bring the ground state electrons into an excited state, and emit light when the electrons return from the excited state to the ground state. When a glass substrate is used and a polycrystalline layer is formed, it is easy to increase the area because light is emitted. However, since a high voltage of several hundred volts is required, the luminous efficiency is very low, and there is a problem that it requires a large power source and lacks simplicity. As described above, conventional organic EL and inorganic EL elements have insufficient performance as light emitters in terms of luminous efficiency, luminance, and lifetime.
これに対し、無機ＥＬの発光輝度と寿命を向上させ、低電圧で駆動させる方法として、活性化された硫化亜鉛ＺｎＳ：Ｃｕ、Ｃｌ発光体を、Ｍｎ存在下で加熱反応させ、ヒ化ガリウムＧａＡｓを有する発光体を製造する製造方法（特許文献１）や、希土類硫化物にｐｒ、Ｍｎ、及びＡｕを添加したものを母体材料とする発光体（特許文献２）が提案されている。また、発光効率を向上させる方法として、ｐ型有機半導体粒子とｎ型有機半導体粒子とが均一に混合されている有機半導体層を用いた光電変換素子が提案（特許文献３）されている。
しかしながら、特許文献１、２に記載の方法では、交流の高電圧を印加する必要があるため効率の向上が望めず、簡易性に欠けるという課題が有る。また、絶縁破壊を起こしやすいために発光の寿命が非常に短い、と言う課題が有る。また、特許文献３に記載の方法では、発光効率のばらつきが大きく、寿命が短いという課題がある。以上より、本発明は、高い発光効率が得られ、寿命の長い発光素子を提供することを課題とする。 However, the methods described in Patent Documents 1 and 2 have a problem that the improvement in efficiency cannot be expected because it is necessary to apply an alternating high voltage, and the simplicity is lacking. In addition, there is a problem that the lifetime of light emission is very short because dielectric breakdown tends to occur. In addition, the method described in Patent Document 3 has a problem that variation in light emission efficiency is large and life is short. In view of the above, an object of the present invention is to provide a light-emitting element with high light emission efficiency and a long lifetime.
本発明者らは、無機材料粒子の粒径を特定し、発光中心剤を添加することで上記課題を解決した。すなわち本発明は、
（１）発光層と該発光層を介して、互いに対向する陽極と陰極とから構成される発光素子であって、該発光層が、数平均粒径が０．３ｎｍから１００．０ｎｍである複数の無機結晶粒子を含有し、かつ、前記複数の無機結晶粒子の少なくとも一つに発光中心剤が付活されていることを特徴とする発光素子、
（２）前記無機結晶粒子が、ｐ型無機半導体粒子および／またはｎ型無機半導体粒子であることを特徴とする（１）に記載の発光素子、
（３）前記無機結晶粒子が、周期表第１３族元素と周期表第１５族元素との化合物を含有する粒子および／または周期表第１２族元素と周期表第１６族元素との化合物を含有する粒子であることを特徴とする（１）に記載の発光素子、
（４）前記発光中心剤が、少なくとも、テルビウム、ユーロピウム、セリウム、マンガン、銅、アルミニウム、銀のいずれか一つを含有することを特徴とする（１）から（３）のいずれかに記載の発光素子、
The inventors of the present invention have solved the above problems by specifying the particle diameter of the inorganic material particles and adding an emission center agent. That is, the present invention
(1) A light-emitting element composed of a light-emitting layer and an anode and a cathode that face each other with the light-emitting layer interposed therebetween, and the light-emitting layer has a number average particle diameter of 0.3 nm to 100.0 nm. A light-emitting element characterized in that an emission center agent is activated in at least one of the plurality of inorganic crystal particles,
(2) The light-emitting element according to (1), wherein the inorganic crystal particles are p-type inorganic semiconductor particles and / or n-type inorganic semiconductor particles,
(3) The inorganic crystal particles include particles containing a compound of a Group 13 element of the periodic table and a Group 15 element of the periodic table and / or a compound of a Group 12 element of the periodic table and a Group 16 element of the periodic table The light emitting device according to (1), wherein the light emitting device
(4) The luminescent center agent contains at least one of terbium, europium, cerium, manganese, copper, aluminum, and silver, according to any one of (1) to (3) Light emitting element,
（５）発光中心剤と、周期表第１３族元素と周期表第１５族元素との化合物と、周期表第１２族元素と周期表第１６族元素との化合物とを含有する溶液を、第一の電極上に塗布した後、加熱することにより、発光層を形成する工程と、前記発光層上に、第一の電極とは異なる極性を有する第二の電極を形成する工程とから構成される発光素子の製造方法であって、前記第一の電極または前記第二の電極のいずれか一方が透明電極であることを特徴とする（４）に記載の発光素子の製造方法、
に関する。
(5) A solution containing a luminescent center agent, a compound of a periodic table group 13 element and a periodic table group 15 element, and a compound of a periodic table group 12 element and a periodic table group 16 element, It is composed of a step of forming a light-emitting layer by heating after coating on one electrode and a step of forming a second electrode having a polarity different from that of the first electrode on the light-emitting layer. The method for manufacturing a light emitting device according to (4), wherein either the first electrode or the second electrode is a transparent electrode,
About.
本発明の発光素子は、発光中心剤が付活された無機結晶ナノ粒子を用いており、直流低電圧で駆動できるために発光効率に優れるという効果がある。さらに、粒径が小さく、絶縁破壊を起こしにくいため寿命が長く、全て無機材料から構成できるために耐久性に優れるという効果がある。 The light-emitting element of the present invention uses inorganic crystal nanoparticles in which a luminescent centering agent is activated, and can be driven with a direct current low voltage, and thus has an effect of excellent luminous efficiency. Furthermore, since the particle size is small and dielectric breakdown is unlikely to occur, the lifetime is long, and since all can be made of an inorganic material, there is an effect that the durability is excellent.
以下、本発明を実施することのできる形態について詳細に説明する。本発明の発光素子は、発光層と該発光層を介して、互いに対向する陽極と陰極とから構成される発光素子であって、該発光層が、数平均粒径が０．３ｎｍから１００．０ｎｍでである複数の無機結晶粒子を含有し、かつ、前記複数の無機結晶粒子の少なくとも一つに発光中心剤が付活されていることを特徴とする発光素子である。また、本発明における発光素子においては、発光は電子と正孔を局在化させる発光中心剤にて起きる。 Hereinafter, embodiments capable of carrying out the present invention will be described in detail. The light-emitting element of the present invention is a light-emitting element composed of a light-emitting layer and an anode and a cathode facing each other with the light-emitting layer interposed therebetween, and the light-emitting layer has a number average particle size of 0.3 nm to 100. A light-emitting element comprising a plurality of inorganic crystal particles having a thickness of 0 nm and having an emission center agent activated on at least one of the plurality of inorganic crystal particles. In the light emitting device of the present invention, light emission is caused by a luminescent center agent that localizes electrons and holes.
[無機結晶粒子]
(粒径)
本発明で用いる、無機結晶粒子は、発光性能の観点から、数平均粒径が、０．３ｎｍから１００．０ｎｍであることを特徴としている。より好ましい数平均粒径は０．３ｎｍ〜２０．０ｎｍ、さらに好ましい数平均粒径は２．０ｎｍ〜１０．０ｎｍである。粒子の粒径が０．３ｎｍ未満の場合、結晶が小さすぎるために独立した結晶としての機能を発現せず、１００．０ｎｍより大きいとキャリアが粒子界面を流れる方が支配的となり発光の効率が低下する。
[Inorganic crystal particles]
(Particle size)
The inorganic crystal particles used in the present invention are characterized in that the number average particle diameter is from 0.3 nm to 100.0 nm from the viewpoint of light emission performance. A more preferable number average particle size is 0.3 nm to 20.0 nm, and a more preferable number average particle size is 2.0 nm to 10.0 nm. When the particle size is less than 0.3 nm, the crystal is too small to exhibit the function as an independent crystal. When the particle size is greater than 100.0 nm, the carrier flows predominantly at the particle interface, and the efficiency of light emission is increased. descend.
無機半導体粒子の数平均粒径は、通常透過型電子顕微鏡による観察で測定するが、半導体結晶に含有される元素の原子番号が小さいために電子線によるコントラストが得にくい場合には、原子間力顕微鏡（ＡＦＭ）による観察なども組み合わせて測定する。なお、数平均粒径の算出するには、２００個程度の粒子の粒径を上記方法で測定し、それらの平均値を計算すればよい。半導体結晶粒子の粒径分布は特に限定されないが、発光波長幅を狭くしたい場合には、標準偏差として±４０％以内、好ましくは±３０％以内、更に好ましくは±２０％以内である。
本発明で規定される数平均粒径を有する無機半導体粒子を用いることで、直流の電圧を印加しても、電子や正孔という電流を担うキャリアが粒子界面を流れることなくなり、無機半導体粒子間を電子がホッピングすることにより伝導が起きる。また、電子や正孔というキャリアが、付活された発光中心剤に局在化されて電子と正孔の再結合が起きやすくなるために効率の良い発光が得られる。
The number average particle size of inorganic semiconductor particles is usually measured by observation with a transmission electron microscope. When the atomic number of the element contained in the semiconductor crystal is small, it is difficult to obtain contrast by an electron beam. Measurement is also performed in combination with observation with a microscope (AFM). In order to calculate the number average particle size, the particle size of about 200 particles is measured by the above method, and the average value thereof is calculated. The particle size distribution of the semiconductor crystal particles is not particularly limited. However, when it is desired to narrow the emission wavelength width, the standard deviation is within ± 40%, preferably within ± 30%, and more preferably within ± 20%.
By using inorganic semiconductor particles having a number average particle size defined in the present invention, carriers carrying currents such as electrons and holes do not flow through the particle interface even when a DC voltage is applied, and between inorganic semiconductor particles Conduction occurs when the electrons hop. In addition, since carriers such as electrons and holes are localized in the activated luminescent center agent and recombination of electrons and holes is likely to occur, efficient light emission can be obtained.
（ｐ型無機半導体粒子、ｎ型無機半導体粒子）
本発明における無機結晶粒子は、ｐ型無機半導体粒子および／またはｎ型半導体粒子であることが好ましい。また、発光層内には、複数の無機結晶粒子が存在し、各々がｐ型無機半導体粒子またはｎ型半導体粒子となっている。発光層全体では、発光層内に、少なくとも、ｐ型無機半導体粒子またはｎ型半導体粒子のいずれか一方が含まれていればよく、ｐ型無機半導体粒子とｎ型半導体粒子の両方が含まれていてもよい。特に、ｐ型無機半導体粒子とｎ型無機半導体粒子の両方を含有する発光層は、キャリア移動の円滑性が向上するため好ましい。
(P-type inorganic semiconductor particles, n-type inorganic semiconductor particles)
The inorganic crystal particles in the present invention are preferably p-type inorganic semiconductor particles and / or n-type semiconductor particles. In the light emitting layer, there are a plurality of inorganic crystal particles, each of which is a p-type inorganic semiconductor particle or an n-type semiconductor particle. In the entire light emitting layer, it is sufficient that at least one of p-type inorganic semiconductor particles or n-type semiconductor particles is contained in the light-emitting layer, and both p-type inorganic semiconductor particles and n-type semiconductor particles are contained. May be. In particular, a light-emitting layer containing both p-type inorganic semiconductor particles and n-type inorganic semiconductor particles is preferable because the smoothness of carrier movement is improved.
本発明における発光素子においては、発光層がｐ型無機半導体粒子、ｎ型無機半導体粒子のどちらか一方で構成される場合にも、ｐ型無機半導体粒子とｎ型無機半導体粒子の両方で構成される場合にも、ｐ型無機半導体粒子、ｎ型の無機半導体を構成する無機化合物は特に限定されず、各々独立に選択され、通常の半導体ドーピングの考え方に従って形成することができる。
発光層が、ｐ型無機半導体粒子、ｎ型無機半導体粒子の両方で構成される場合には、２種類以上の無機化合物の構成元素を相互に拡散させることにより、該無機化合物の一方を、ｐ型半導体にし、（以下、ｐ型化とも言う）、他方をｎ型半導体にする（以下、ｎ型化とも言う）ことによって、ｐ型無機半導体粒子およびｎ型無機半導体粒子生成させることが有効である。さらに、キャリア濃度が類似したドーピングが一度にできるので好ましい。また、ｐ型無機半導体粒子およびｎ型無機半導体粒子生成に用いることのできる無機化合物としては、例えば、一元系無機化合物や、二元系、三元系等の多元系無機化合物を用いることができる。
In the light emitting device of the present invention, the light emitting layer is composed of both p type inorganic semiconductor particles and n type inorganic semiconductor particles even when the light emitting layer is composed of either p type inorganic semiconductor particles or n type inorganic semiconductor particles. In this case, the inorganic compounds constituting the p-type inorganic semiconductor particles and the n-type inorganic semiconductor are not particularly limited, and can be selected independently and formed according to the usual concept of semiconductor doping.
In the case where the light emitting layer is composed of both p-type inorganic semiconductor particles and n-type inorganic semiconductor particles, one of the inorganic compounds is converted to p by diffusing constituent elements of two or more kinds of inorganic compounds with each other. It is effective to generate p-type inorganic semiconductor particles and n-type inorganic semiconductor particles by using a p-type semiconductor (hereinafter also referred to as p-type) and an n-type semiconductor (hereinafter also referred to as n-type semiconductor). is there. Furthermore, it is preferable because doping with a similar carrier concentration can be performed at one time. Moreover, as an inorganic compound which can be used for generation of p-type inorganic semiconductor particles and n-type inorganic semiconductor particles, for example, one-component inorganic compounds and multi-component inorganic compounds such as binary and ternary can be used. .
ここで、ｐ型化、ｎ型化の一例として、２種類の二元系無機化合物を用いた場合について説明する。例えば、ＺｎＯとＧａＮという２種類の二元系無機化合物を用いた場合、ＧａＮの構成元素であるＧａを、ＺｎＯに拡散させることでＺｎＯがｎ型化し、ＺｎＯの構成元素であるＺｎをＧａＮに拡散させることによってＧａＮがｐ型化する。これにより、ＺｎＯにＧａがドープされたｎ型半導体粒子と、ＧａＮにＺｎがドープされたｐ型半導体粒子を生成することができる。また、同じ化合物を用いた場合でもＧａＮの構成元素であるＮを、ＺｎＯに拡散させることでＺｎＯがｐ型化し、ＺｎＯの構成元素であるＯをＧａＮに拡散させることによってＧａＮがｐ型化する。これにより、ＺｎＯにＮがドープされたｐ型半導体粒子と、ＧａＮにＯがドープされたｐ型半導体粒子を生成することができる。 Here, a case where two types of binary inorganic compounds are used will be described as an example of p-type and n-type. For example, when two types of binary inorganic compounds, ZnO and GaN, are used, Ga, which is a constituent element of GaN, is diffused into ZnO, so that ZnO becomes n-type, and Zn, which is a constituent element of ZnO, is converted into GaN. By diffusing, GaN becomes p-type. Thus, n-type semiconductor particles in which ZnO is doped with Ga and p-type semiconductor particles in which GaN is doped with Zn can be generated. Further, even when the same compound is used, ZnO becomes p-type by diffusing N, which is a constituent element of GaN, into ZnO, and GaN becomes p-type by diffusing O, which is a constituent element of ZnO, into GaN. . Thereby, p-type semiconductor particles in which ZnO is doped with N and p-type semiconductor particles in which GaN is doped with O can be generated.
また、本発明において、２種類以上の無機化合物の構成元素を相互に拡散させる方法をいくつか例示することができる。例えば、発光層を形成する２種以上の無機化合物粒子の分散液を作製し、それを電極が形成された基板上に塗布した後、所定の雰囲気中、例えば、Ａｒ、Ｘｅ、Ｎｅ、窒素等の不活性ガス中で熱処理を行えばよい。なお、本発明において、加熱処理時に用いられるものは、上記不活性ガスに限られるものではなく、使用する無機材料に応じて、酸素や硫黄、硫化水素等を用いることもできる。別な方法として、例えば、発光層を電子線蒸着で形成する場合、双方の半導体を所定量で混合した蒸着源を用いる、もしくは別々の蒸着源に独立に電子線を照射して蒸着する方法で、基板温度を互いに拡散する温度にしながら蒸着する方法も挙げられる。 In the present invention, several methods of diffusing constituent elements of two or more kinds of inorganic compounds can be exemplified. For example, after preparing a dispersion of two or more kinds of inorganic compound particles forming the light emitting layer and applying it to a substrate on which an electrode is formed, in a predetermined atmosphere, for example, Ar, Xe, Ne, nitrogen, etc. Heat treatment may be performed in an inert gas. In addition, what is used at the time of heat processing in this invention is not restricted to the said inert gas, According to the inorganic material to be used, oxygen, sulfur, hydrogen sulfide, etc. can also be used. As another method, for example, when the light emitting layer is formed by electron beam evaporation, an evaporation source in which both semiconductors are mixed in a predetermined amount is used, or a separate evaporation source is independently irradiated with an electron beam for evaporation. Further, there is a method of vapor deposition while keeping the substrate temperature at a temperature that diffuses to each other.
(無機化合物)
本発明の無機結晶粒子に用いることのできる無機化合物は、ｐ型化、ｎ型化するものであれば特に限定されるものではない。これらの無機化合物としては、例えば一元系無機化合物や、二元系、三元系等の多元系無機化合物を用いることができる。
本発明における無機結晶粒子は、周期表第１３族元素と周期表第１５族元素との化合物（以下、III−V族化合物とも言う）を含有する粒子および／または周期表第１２族元素と周期表第１６族元素との化合物（以下、II−VI族化合物とも言う）を含有する粒子であることが好ましい。また、発光層内には、複数の無機結晶粒子が存在し、各々の無機結晶粒子がIII−V族化合物またはII−VI族化合物を含有している。発光層全体では、少なくとも、III−V族化合物またはII−VI族化合物のいずれか一方を含んでいればよく、III−V族化合物とII−VI族化合物の両方を含んでいてもよい。
(Inorganic compounds)
The inorganic compound that can be used for the inorganic crystal particles of the present invention is not particularly limited as long as it is p-type or n-type. As these inorganic compounds, for example, one-component inorganic compounds and multi-component inorganic compounds such as binary and ternary compounds can be used.
The inorganic crystal particles in the present invention include particles containing a compound of Group 13 elements of the periodic table and Group 15 elements of the periodic table (hereinafter also referred to as III-V compounds) and / or Group 12 elements of the periodic table and periodicity. Particles containing a compound with a Group 16 element in the table (hereinafter also referred to as II-VI group compound) are preferable. A plurality of inorganic crystal particles exist in the light emitting layer, and each inorganic crystal particle contains a III-V group compound or a II-VI group compound. The entire light-emitting layer may contain at least one of the III-V group compound or the II-VI group compound, and may contain both the III-V group compound and the II-VI group compound.
(互いにｐ型化、ｎ型化する無機化合物)
本発明では、互いにｐ型化、ｎ型化する無機化合物を用いることが好ましい。特に、III−V族化合物とII−VI族化合物の組み合わせは、容易にｐ型化、ｎ型化する傾向があるため好ましい。具体的には、III−V族化合物にII族（周期表第１２族元素）が拡散してIII−V族化合物がｐ型化し、II−VI族化合物にIII族（周期表第１３族元素）が拡散してII−VI族化合物がｎ型化する。このように、互いにｐ型化、ｎ型化する無機化合物の組み合わせとしては、他に、III−V族化合物とIV族（周期表第１６族）単体および化合物の組み合わせが挙げられる。また、上記例では、２種類の二元系無機化合物の組み合わせや、二元系無機化合物と一元系無機化合物の組み合わせの場合を挙げているが、本発明で用いることのできるｐ型化、ｎ型化する無機化合物の種類や組み合わせは、これに限定されるものではない。例えば、２種類の三元系無機化合物の組み合わせや、二元系無機化合物と三元系無機化合物の組み合わせ等も用いることができる。
(Inorganic compounds that p-type and n-type each other)
In the present invention, it is preferable to use inorganic compounds that are p-type and n-type each other. In particular, a combination of a III-V group compound and a II-VI group compound is preferable because it tends to easily become p-type and n-type. Specifically, a group II (group 12 element of the periodic table) diffuses into a group III-V compound to form a p-type group III-V compound, and a group III (group 13 element of the periodic table) ) Diffuses and the II-VI group compound becomes n-type. As described above, the combination of inorganic compounds which are converted to p-type and n-type each other includes a combination of a group III-V compound, a group IV (group 16 of the periodic table), and a compound. In the above example, a combination of two types of binary inorganic compounds or a combination of a binary inorganic compound and a single inorganic compound is cited. However, p-type and n can be used in the present invention. The type and combination of inorganic compounds to be molded are not limited to this. For example, a combination of two kinds of ternary inorganic compounds or a combination of a binary inorganic compound and a ternary inorganic compound can be used.
(ｐ型化する無機化合物)
ｐ型化する無機化合物としては、ＮｉＯ、ＣｕＡｌＯ２、ＣｕＡｌＯ２、ＺｎＲｈ２Ｏ２、Ｃｕ２Ｓ、ＳｒＣｕ２Ｏ２、ＬａＣｕＯＳ、ＺｎＭｇＯ４、Ｓｉ、Ｇｅ、ＺｎＳｅ、ＺｎＴｅ、ＣｄＳｅ、ＣｄＴｅ、ＣｕＩｎＳ２、ＣｕＩｎＴｅ２、ＣｕＡｌＳｅ２、ＣｕＧａＳｅ２、ＣｕＩｎ５Ｓｅ８、ＧａＡｓ、ＩｎＡｓ、ＡｌＳｂ、ＧａＳｂ、ＩｎＳｂ等を挙げることができ、ＣｕＡｌＯ２、ＺｎＴｅ、ＣｄＳｅ、ＣｄＴｅ、ＣｕＩｎＳ２、ＣｕＧａＳｅ２、ＧａＡｓ、ＩｎＡｓ、ＡｌＳｂ、ＧａＳｂ、ＩｎＳｂ、Ｓｉ、Ｇｅが特に好ましい。
(Inorganic compounds that turn into p-type)
Examples of inorganic compounds to be converted to p-type include NiO, CuAlO 2 , CuAlO 2 , ZnRh 2 O 2 , Cu 2 S, SrCu 2 O 2 , LaCuOS, ZnMgO 4 , Si, Ge, ZnSe, ZnTe, CdSe, CdTe, and CuInS 2. , CuInTe 2 , CuAlSe 2 , CuGaSe 2 , CuIn 5 Se 8 , GaAs, InAs, AlSb, GaSb, InSb, and the like. CuAlO 2 , ZnTe, CdSe, CdTe, CuInS 2 , CuGaSe 2 , GaAs, InAs, AlSb, GaSb, InSb, Si, and Ge are particularly preferable.
(ｎ型化する無機化合物)
ｎ型化する無機化合物としては、ＺｎＯ、ＧａＮ、ＺｎＳｅ、ＺｎＳ、ＳｎＯ２、ＺｎＳｅ、ＺｎＴｅ、ＣｄＳ、ＣｄＳｅ、ＣｄＴｅ、ＣｕＩｎＳ２、ＣｕＩｎＳｅ２、ＣｕＩｎ５Ｓｅ８、ＣｕＧａＳｅ２、ＣｕＩｎＴｅ２、ＳｒＳ，ＢａＡｌ２Ｓ４、ＣａＧａ２Ｓ４、ＢａＭｇＡｌ２Ｓ４、ＣａＡｌ２Ｓ４等のＩＩａ−ＩＩＩｂ２−Ｓ４で構成される材料、ＺｎＭｇＳ、ＣａＳ、ＳｒＧａ２Ｓ４、ＭｇＧａ2Ｏ４、ＢａＺｎＳ等を挙げることができる。この中でも発光中心が付活されて発光しやすいと言う観点で、ＺｎＳ、ＳｒＳ，ＢａＡｌ２Ｓ４、ＣａＧａ２Ｓ４、ＢａＭｇＡｌ２Ｓ４、ＣａＡｌ２Ｓ４等のＩＩａ−ＩＩＩｂ２−Ｓ４で構成される材料、ＺｎＭｇＳ、ＣａＳ、ＳｒＧａ２Ｓ４、ＭｇＧａ2Ｏ４、ＢａＺｎＳが特に好ましい。
(N-type inorganic compound)
As the inorganic compound to n-type, ZnO, GaN, ZnSe, ZnS , SnO 2, ZnSe, ZnTe, CdS, CdSe, CdTe, CuInS 2, CuInSe 2, CuIn 5 Se 8, CuGaSe 2, CuInTe 2, SrS, BaAl materials composed of 2 S 4, CaGa 2 S 4 , BaMgAl 2 S 4, CaAl 2 S IIa-IIIb2-S4 , such as 4, ZnMgS, CaS, SrGa 2 S 4, MgGa 2 O 4, be given BaZnS like Can do. Among these, from the viewpoint that the emission center is activated and it is easy to emit light, it is composed of IIa-IIIb2-S4 such as ZnS, SrS, BaAl 2 S 4 , CaGa 2 S 4 , BaMgAl 2 S 4 , CaAl 2 S 4 and the like. Particularly preferred are ZnMgS, CaS, SrGa 2 S 4 , MgGa 2 O 4 and BaZnS.
（無機半導体粒子の構造）
本発明における無機半導体粒子の構造として、粒子間をキャリアが流れることを抑制してキャリア輸送性を高めるために内殻（コア）と外殻（シェル）からなる所謂コア−シェル構造とすることも好ましく用いられる。内核（コア）と外殻（シェル）からなるいわゆるコア−シェル構造とすると、コアを成す半導体結晶の量子効果による発光能も改良される場合があり好適である。コア−シェル構造の場合、コアを形成する半導体結晶構造よりもバンドギャップエネルギーの大きな半導体結晶構造をシェルとして起用することにより、コア形成する半導体結晶界面を流れる電流を抑制でき、また発光効率を減衰させる表面準位や結晶格子欠陥準位等を経由するエネルギー損失を防ぐことが可能である。
(Structure of inorganic semiconductor particles)
The inorganic semiconductor particles in the present invention may have a so-called core-shell structure composed of an inner shell (core) and an outer shell (shell) in order to suppress carrier flow between the particles and improve carrier transportability. Preferably used. A so-called core-shell structure including an inner core (core) and an outer shell (shell) is preferable because the light emission ability due to the quantum effect of the semiconductor crystal forming the core may be improved. In the case of the core-shell structure, by using a semiconductor crystal structure having a larger band gap energy than the semiconductor crystal structure forming the core as the shell, the current flowing through the semiconductor crystal interface forming the core can be suppressed, and the luminous efficiency is attenuated. It is possible to prevent energy loss via the surface level and crystal lattice defect level to be generated.
このようなコア−シェル構造におけるシェルに好適に用いられる半導体結晶としては、通常、温度３００Ｋのバルク状態におけるバンドギャップが、２．０ｅV以上、好ましくは、２．３ｅV以上、さらに好ましくは２．５ｅV以上であるものが挙げられる。なお、バンドギャップはコアを形成する半導体結晶のバンドギャップエネルギーとの関係で決まるものである。
具体的には、例えば、周期表第１３族元素と周期表第１５族元素との化合物（III−V族化合物）；周期表第１２族元素と周期表第１６族元素との化合物（II−VI族化合物）；周期表第２族元素と周期表第１６族元素との化合物等が好適に用いられる。これらの中、好ましいシェルとなる半導体結晶組成は、ＢＮ、ＢＡｓ、ＧａＮ等のIII−V族化合物；ＺｎＯ、ＺｎＳ、ＺｎＳｅ、ＣｄＳ等のII−VI族化合物；ＭｇＳ、ＭｇＳｅ等の周期表第２族元素と周期表第１６族元素との化合物等が挙げられる。また、最も好ましいのは、ＢＮ、ＢＡｓ、ＧａＮ、ＺｎＯ、ＺｎＳ、ＺｎＳｅ、ＭｇＳ、ＭｇＳｅ等である。 また、上述した二元系無機化合物のほか、一元系無機化合物や、三元系等の多元系無機化合物を用いることもできる。なお、コアに用いられる半導体結晶としては、上記シェルに用いられる半導体結晶と好適にコアーシェルを形成できるものであればよい。
As a semiconductor crystal suitably used for the shell in such a core-shell structure, the band gap in a bulk state at a temperature of 300 K is usually 2.0 eV or more, preferably 2.3 eV or more, more preferably 2.5 eV. The thing which is the above is mentioned. The band gap is determined by the relationship with the band gap energy of the semiconductor crystal forming the core.
Specifically, for example, a compound of a Group 13 element of the periodic table and a Group 15 element of the periodic table (III-V compound); a compound of a Group 12 element of the periodic table and a Group 16 element of the periodic table (II- Group VI compounds); compounds of Group 2 elements of the periodic table and Group 16 elements of the periodic table are preferably used. Among these, the preferred semiconductor crystal composition of the shell is a III-V group compound such as BN, BAs, GaN; II-VI group compound such as ZnO, ZnS, ZnSe, CdS; And compounds of group elements and group 16 elements of the periodic table. Most preferred are BN, BAs, GaN, ZnO, ZnS, ZnSe, MgS, MgSe, and the like. In addition to the binary inorganic compound described above, a single inorganic compound or a multi-component inorganic compound such as a ternary inorganic compound can also be used. In addition, as a semiconductor crystal used for a core, what can form a core shell suitably with the semiconductor crystal used for the said shell is sufficient.
[発光層]
（発光層内での分散状態）
本発明では、発光層内でｐ型半導体粒子および／またはｎ型無機半導体粒子が均一に分散していることが好ましい。均一に分散しているとは、ｐ型無機半導体粒子および／またはｎ型無機半導体粒子が発光層内で均一に分布しており、特定の積層構造をもたないことを言う。特に発光層がｐ型無機半導体粒子、ｎ型無機半導体粒子の両方で構成される場合、均一に分散することにより、二つの化合物材料の接点をより多くできて好ましい。ｐ型無機半導体粒子とｎ型無機半導体粒子の混合比は必ずしも限定されないが、片方が少なすぎると両方が入っている効果が発現しない。そのため、ｐ型無機半導体粒子とｎ型無機半導体粒子の比率は、モル比で好ましくは８：２〜２：８の範囲であり、より好ましくは７：３〜３：７の範囲であり、さらに好ましくは６：４〜４：６の範囲である。但し、無機材料においては正孔の移動度が小さいため、ｐ型無機半導体粒子を多めに用いるのが好ましい場合が多い。
[Light emitting layer]
(Dispersed state in the light emitting layer)
In the present invention, it is preferable that the p-type semiconductor particles and / or the n-type inorganic semiconductor particles are uniformly dispersed in the light emitting layer. Uniformly dispersed means that the p-type inorganic semiconductor particles and / or the n-type inorganic semiconductor particles are uniformly distributed in the light emitting layer and do not have a specific laminated structure. In particular, in the case where the light emitting layer is composed of both p-type inorganic semiconductor particles and n-type inorganic semiconductor particles, it is preferable to uniformly disperse the two compound materials to increase the number of contacts. The mixing ratio of the p-type inorganic semiconductor particles and the n-type inorganic semiconductor particles is not necessarily limited, but if one of them is too small, the effect of containing both does not appear. Therefore, the ratio of the p-type inorganic semiconductor particles and the n-type inorganic semiconductor particles is preferably in the range of 8: 2 to 2: 8, more preferably in the range of 7: 3 to 3: 7 in terms of molar ratio, Preferably it is the range of 6: 4-4: 6. However, since the mobility of holes is small in inorganic materials, it is often preferable to use a large amount of p-type inorganic semiconductor particles.
また、ｐ型無機半導体粒子および／またはｎ型無機半導体粒子が発光層内で均一に分布する発光層では、該ｐ型無機半導体粒子および／またはｎ型無機半導体粒子を構成する無機化合物、例えば、III−V族化合物および／またはII−VI族化合物が均一に分散していることとなる。従って、ｐ型無機半導体粒子とｎ型無機半導体粒子の混合比の制御は、該ｐ型無機半導体粒子および／またはｎ型無機半導体粒子を構成する無機化合物、例えば、III−V族化合物および／またはII−VI族化合物の混合比を調整することによって、達成することができる。また、上述した二元系無機化合物以外に、一元系無機化合物や、三元系等の多元系無機化合物を用いる場合も、同様に、一元系無機化合物あるいは多元系無機化合物の混合比を調整することによって、ｐ型無機半導体粒子とｎ型無機半導体粒子の混合比を調整することができる。 In the light emitting layer in which the p-type inorganic semiconductor particles and / or the n-type inorganic semiconductor particles are uniformly distributed in the light-emitting layer, an inorganic compound constituting the p-type inorganic semiconductor particles and / or the n-type inorganic semiconductor particles, for example, The III-V group compound and / or the II-VI group compound are uniformly dispersed. Therefore, the control of the mixing ratio of the p-type inorganic semiconductor particles and the n-type inorganic semiconductor particles is controlled by the inorganic compounds constituting the p-type inorganic semiconductor particles and / or the n-type inorganic semiconductor particles, for example, III-V group compounds and / or This can be achieved by adjusting the mixing ratio of the II-VI compound. In addition to the binary inorganic compound described above, when using a single inorganic compound or a multi-component inorganic compound such as a ternary system, the mixing ratio of the single-component inorganic compound or the multi-component inorganic compound is similarly adjusted. Thus, the mixing ratio of the p-type inorganic semiconductor particles and the n-type inorganic semiconductor particles can be adjusted.
（膜厚）
本発明における発光素子の発光層の膜厚は特に限定されるものではないが、好ましくは１００．０ｎｍ〜１０μｍの範囲であり、より好ましくは２００ｎｍ〜５μｍの範囲である。１００．０ｎｍよりも薄いと発光量が不十分となり、１０μｍよりも厚いと印加すべき電圧が高くなり過ぎる、そのために絶縁破壊がおきやすくなる等の問題が生じる。
(Film thickness)
Although the film thickness of the light emitting layer of the light emitting element in this invention is not specifically limited, Preferably it is the range of 100.0 nm-10 micrometers, More preferably, it is the range of 200 nm-5 micrometers. When the thickness is less than 100.0 nm, the amount of light emission is insufficient, and when the thickness is more than 10 μm, the voltage to be applied becomes too high, which causes problems such as easy breakdown.
[発光中心剤]
本発明における発光中心剤は、発光層内に存在する複数の無機結晶粒子のすくなくとも一つに付活されていればよい。また、ｐ型無機半導体粒子とｎ型無機半導体粒子の少なくとも一方に付活されていれば良く、両方に付活されていても構わない。なお、発光層内の、すべてのｐ型（またはｎ型）無機半導体粒子に発光中心剤が付活されていることは、必ずしも必要でない。すなわち、発光層内で、発光中心剤が付活されているｐ型半導体粒子および／またはｎ型半導体粒子と、発光中心剤が付活されていないｐ型半導体粒子および／またはｎ型半導体粒子とが混在する場合も本発明に含まれる。
[Luminescent agent]
The luminescent centering agent in the present invention may be activated by at least one of the plurality of inorganic crystal particles present in the luminescent layer. Moreover, what is necessary is just to be activated by at least one of the p-type inorganic semiconductor particle and the n-type inorganic semiconductor particle, and it may be activated by both. In addition, it is not always necessary that the luminescent center agent is activated in all the p-type (or n-type) inorganic semiconductor particles in the luminescent layer. That is, p-type semiconductor particles and / or n-type semiconductor particles in which the emission center agent is activated in the light-emitting layer, and p-type semiconductor particles and / or n-type semiconductor particles in which the emission center agent is not activated. Also included in the present invention is a mixture of the above.
また、ｐ型無機半導体粒子とｎ型無機半導体粒子を構成する無機化合物を用いる場合も同様に考えることができる。例えば、III−V族化合物とII−VI族化合物の少なくとも一方に発光中心剤が付活されていればよく、両方に付活されていても構わない。上述した二元系無機化合物以外に、一元系無機化合物、三元系等の多元系無機化合物を用いる場合も、同様に考えることができる。例えば、２種類の三元系無機化合物を用いる場合は、三元系無機化合物の少なくとも一方に発光中心剤が付活されていればよい。
本発明に用いられる発光中心剤としては、電子と正孔を引き付けて再結合確率を向上させる元素であれば特に限定されないが、例えば、テルビウム、ユーロピウム、セリウム、プラセオジウム等の希土類元素、マンガン、銅、アルミニウム、銀、等を用いることが出来る。この中でも、発光中心としての実績が高いテルビウム、ユーロピウム、セリウム、プラセオジウム等の希土類元素、マンガン、銅等が特に好ましく用いられる。
The same applies to the case of using inorganic compounds constituting p-type inorganic semiconductor particles and n-type inorganic semiconductor particles. For example, at least one of the III-V group compound and the II-VI group compound may be activated by the luminescent center agent, and may be activated by both. In addition to the binary inorganic compounds described above, the same can be considered when a multi-component inorganic compound such as a single-component inorganic compound or a ternary inorganic compound is used. For example, when two types of ternary inorganic compounds are used, it is sufficient that the luminescent center agent is activated on at least one of the ternary inorganic compounds.
The emission center agent used in the present invention is not particularly limited as long as it is an element that attracts electrons and holes to improve the recombination probability. For example, rare earth elements such as terbium, europium, cerium, and praseodymium, manganese, copper Aluminum, silver, or the like can be used. Among these, rare earth elements such as terbium, europium, cerium, and praseodymium, manganese, copper, and the like, which have a high track record as emission centers, are particularly preferably used.
これら発光中心剤は、得ようとする発光波長により、無機半導体粒子との最適な組み合わせを考慮して決定される。電子及び正孔のキャリア輸送を有効に行わせるためには、例えば発光中心剤がＴｂである場合、Ｔｂの励起状態である５ｄ軌道と基底状態である４ｆ軌道が母材の価電子帯上端と伝導体下端の間に存在するように選択される。このような選択を行うことによって、陰極側から注入された電子が無機半導体粒子の伝導体に移動し、次に発光中心剤の励起準位へ移動、さらに発光中心剤の基底準位に遷移する際に発光が得られる。発光中心剤の基底準位に遷移した電子は、無機半導体粒子の価電子帯に移動して電流が流れる。 These emission centering agents are determined in consideration of the optimum combination with inorganic semiconductor particles depending on the emission wavelength to be obtained. In order to effectively carry out electron and hole carrier transport, for example, when the emission centering agent is Tb, the 5d orbital that is the excited state of Tb and the 4f orbital that is the ground state are the top of the valence band of the base material. It is selected to exist between the lower ends of the conductors. By making such a selection, electrons injected from the cathode side move to the conductor of the inorganic semiconductor particles, then move to the excitation level of the emission center agent, and further transition to the ground level of the emission center agent. Light emission is obtained. The electrons that have transitioned to the ground level of the emission center agent move to the valence band of the inorganic semiconductor particles, and a current flows.
無機化合物に発光中心剤を付活させる方法としては、例えば、予め、発光層を形成する材料である無機化合物に発光中心が付活された粒子を形成し、それを塗布して発光層を形成する場合には、発光層を形成する材料である無機化合物と、発光中心剤とが溶解した溶液を作成し、それらを混合して異なる溶媒を入れて溶液から無機物を析出する際に発光中心を無機化合物に付活させる方法等があげられる。この場合には、発光中心が付活された微粒子塗布の後工程において加熱処理を加えることにより、さらに付活性が向上するので好ましい。また、発光層を形成する場合には、無機化合物に必要な濃度の発光中心剤を添加した蒸着元もしくはスパッタターゲットを用いて製膜を行う、もしくは基板を所定温度に加熱しながらそれぞれを別なソースとして共蒸着、共スパッタを行う方法等を挙げる事ができる。この場合も、製膜後に加熱処理を加えることで発光中心の付活性を高めることができて好ましい。 As a method for activating the luminescent center agent in the inorganic compound, for example, particles having the luminescent center activated in advance are formed on the inorganic compound, which is a material for forming the luminescent layer, and applied to form the luminescent layer. In this case, a solution in which the inorganic compound that is a material for forming the light emitting layer and the light emission center agent are dissolved is prepared, and the light emission centers are formed when the inorganic substances are precipitated from the solution by mixing them and adding different solvents. The method of activating to an inorganic compound etc. is mention | raise | lifted. In this case, it is preferable to add heat treatment in the post-process after the fine particle application in which the luminescent center is activated, since the activation is further improved. In addition, when forming a light emitting layer, a film is formed by using a vapor deposition source or a sputtering target to which an emission center agent having a concentration necessary for an inorganic compound is added, or each substrate is heated separately to a predetermined temperature. Examples of the source include a method of co-deposition and co-sputtering. Also in this case, it is preferable to add heat treatment after the film formation to increase the activity of the emission center.
また、発光中心剤が無機半導体粒子に付活される濃度は特に限定されないが、好ましくは無機半導体粒子材に対して０．００１〜５ｍｏｌ％の範囲であり、より好ましくは０．００５〜３ｍｏｌ％の範囲である。０．００１％より少ないと発光量が不十分となり、５ｍｏｌ％より多いと無機半導体粒子と固溶化して別な化合物を形成する、発光した光を自身が吸収してしまい発光の取り出し量が減少する等が起きる。
発光中心剤は、発光層内に存在する複数の無機結晶粒子の少なくとも一つに付活されていればよいが、上記濃度範囲で発光中心剤を付活させることにより、好ましい数の発光中心剤を付活させることができる。
The concentration at which the luminescent center agent is activated by the inorganic semiconductor particles is not particularly limited, but is preferably in the range of 0.001 to 5 mol%, more preferably 0.005 to 3 mol% with respect to the inorganic semiconductor particle material. Range. If the amount is less than 0.001%, the amount of emitted light is insufficient, and if it is more than 5 mol%, it forms a separate compound by forming a solid solution with inorganic semiconductor particles. To happen.
The luminescent center agent may be activated by at least one of the plurality of inorganic crystal particles present in the luminescent layer, but by activating the luminescent center agent in the above concentration range, a preferred number of luminescent center agents can be obtained. Can be activated.
発光中心剤は、少なくとも１種類入っていることが必要である。発光波長は、無機材料と発光中心剤の組み合わせによって決まる。そのため、例えば青色の発光を得たい場合にはそのための無機材料と発光中心剤が選択される。例えば、青色を得ようとする場合にはＳｒＳ；Ｃｅ、ＳｒＳ；Ｃｕ、ＺｎＳ；Ｔｍ、ＣａＧａ２Ｓ４；Ｃｅ、ＢａＡｌ２Ｓ４；Ｅｕ、ＢａＭｇＡｌＯ１７；Ｅｕ、Ｂａ３ＭｇＳｉ２Ｏ８；Ｅｕ等が、緑色を得ようとする場合にはＳｒＧａ２Ｓ４；Ｅｕ、ＺｎＳ；Ｃｕ，Ａｌ、ＺｎＳ；Ｔｂ、ＺｎＧａ２Ｏ４；Ｍｎ等が、赤色を得ようとする場合にはＺｎＳ；Ｅｕ、ＣａＳ；Ｅｕ、Ｙ２ＯＳ；Ｅｕ、Ｌａ２Ｏ２Ｓ；Ｅｕ、ＣａＡｌＳｉＮ３；Ｅｕ、ＣａＡｌＳｉＮ３；Ｅｕ等が挙げられる。発光層を形成する無機材料がナノ粒子である場合には、量子効果により無機材料のバンドギャップが広がるため、例えば上記で緑色発光を示す組み合わせでも青に近い発光を取得できたり、赤色発光を示す組み合わせでも緑色に近い発光を取得できることもある。また、白色を得ようとする場合には、青と緑、または青、緑、赤等の発光を示す複数の発光中心剤が付活されることも好ましく行われる。 It is necessary that at least one luminescent center agent is contained. The emission wavelength is determined by the combination of the inorganic material and the emission center agent. Therefore, for example, when it is desired to obtain blue light emission, an inorganic material and a light emission centering agent are selected. For example, when obtaining blue, SrS; Ce, SrS; Cu, ZnS; Tm, CaGa 2 S 4 ; Ce, BaAl 2 S 4 ; Eu, BaMgAlO 17 ; Eu, Ba 3 MgSi 2 O 8 ; Eu Etc., when trying to obtain a green color, SrGa 2 S 4 ; Eu, ZnS; Cu, Al, ZnS; Tb, ZnGa 2 O 4 ; , CaS; Eu, Y 2 OS; Eu, La 2 O 2 S; Eu, CaAlSiN 3 ; Eu, CaAlSiN 3 ; Eu, and the like. When the inorganic material forming the light-emitting layer is a nanoparticle, the band gap of the inorganic material is widened due to the quantum effect. Even in combination, light emission close to green may be obtained. In order to obtain white, it is also preferable to activate a plurality of luminescent centering agents that emit light such as blue and green, or blue, green, and red.
[基板]
本発明における発光素子に用いられる基板の種類は特に限定されない。サファイア、ＭｇＯ、ＳｉＣ、Ｓｉ、ＧａＡｓ等の単結晶基板でも良く、ガラスやポリエチレンテレフタレート、ポリエチレン、ポリプロピレン、等のプラスチック基板でも良い。発光層で生じた光を基板を通して取り出そうとする場合には、基板は透明である必要がある。不透明な基板を用いる場合には、上部の電極を透明とする。基板の中でも、安価で透明であるために自由度が広がると言う点で、ガラス、プラスチックが好ましい。
[substrate]
The kind of the substrate used for the light emitting device in the present invention is not particularly limited. Single crystal substrates such as sapphire, MgO, SiC, Si, and GaAs may be used, and plastic substrates such as glass, polyethylene terephthalate, polyethylene, and polypropylene may be used. In order to extract light generated in the light emitting layer through the substrate, the substrate needs to be transparent. When an opaque substrate is used, the upper electrode is transparent. Among the substrates, glass and plastic are preferable because they are inexpensive and transparent, and thus have a large degree of freedom.
[電極]
本発明における発光素子では、発光素子に電圧を印加するために発光層の両側に電極を配する必要がある。用いられる電極の種類は特に限定されず、ＩＴＯ、ＺｎＯ、ＳｎＯ２等の透明電極、Ａｕ、Ａｇ、Ｎｉ、Ｃｕ、Ｔｉ、Ｍｇ、Ｃｕ、ｐｔ、Ｃａ等の金属電極、あるいはそれらの合金であるマグネシウム−銀合金、マグネシウム−インジウム合金、アルミニウム−リチウム合金、Ｃ１２Ａ７などの複合化合物電極を用いることができる。ここで、Ｃ１２Ａ７とは、１２ＣａＯ・７Ａｌ２Ｏ３で表されるカルシアアルミナ化合物で、籠状構造を有する酸化物材料である。籠状構造の中に、ＯＨ−、Ｏ２ −、Ｈ−、ｅ―等を含む場合があるが、それら全てを表す。また、発光層で生じた発光を外部に取り出すために少なくとも一方の電極が透明であることが必要である。
[electrode]
In the light emitting device of the present invention, it is necessary to dispose electrodes on both sides of the light emitting layer in order to apply a voltage to the light emitting device. The kind of electrode used is not particularly limited, and is a transparent electrode such as ITO, ZnO, SnO 2 , a metal electrode such as Au, Ag, Ni, Cu, Ti, Mg, Cu, pt, Ca, or an alloy thereof. A composite compound electrode such as a magnesium-silver alloy, a magnesium-indium alloy, an aluminum-lithium alloy, or C12A7 can be used. Here, C12A7 is a calcia alumina compound represented by 12CaO.7Al 2 O 3 and is an oxide material having a cage structure. The cage structure may contain OH − , O 2 − , H − , e −, etc., all of which are represented. In addition, at least one of the electrodes needs to be transparent in order to extract light emitted from the light emitting layer to the outside.
発光素子中の電子や正孔のキャリア輸送を有効に起こさせるためには、例えば陽極側の電極は仕事関数が大きな材料が好ましく、陰極側の電極には仕事関数の小さな材料が好ましい。それにより、陰極側において電極から発光層の伝導体への電子移動が、陽極側においては発光層の価電子帯から電極への電子移動が有効に行われる。低仕事関数金属からなる陰極を保護するために、陰極上に仕事関数が高く、安定な金属を積層することにより、素子の安定性を高めることが出来る。このような金属としては、例えば、銀、銅、ニッケル、クロム、金、白金等が挙げられる。
電極の膜厚は特に限定されないが、薄すぎると伝導性が確保されない。また、必要以上に厚過ぎると形成時間が長くなりすぎる。そのため、好ましくは１０ｎｍ〜１μｍの範囲であり、より好ましくは３０ｎｍ〜０．５μｍの範囲である。
In order to effectively cause carrier transport of electrons and holes in the light emitting element, for example, a material having a high work function is preferable for the electrode on the anode side, and a material having a low work function is preferable for the electrode on the cathode side. Thereby, the electron transfer from the electrode to the conductor of the light emitting layer is effectively performed on the cathode side, and the electron transfer from the valence band of the light emitting layer to the electrode is effectively performed on the anode side. In order to protect the cathode made of a low work function metal, the stability of the device can be improved by laminating a stable metal having a high work function on the cathode. Examples of such a metal include silver, copper, nickel, chromium, gold, and platinum.
The film thickness of the electrode is not particularly limited, but if it is too thin, conductivity cannot be ensured. On the other hand, if it is too thick, the formation time becomes too long. Therefore, it is preferably in the range of 10 nm to 1 μm, more preferably in the range of 30 nm to 0.5 μm.
[キャリア輸送層]
本発明における発光素子では、本発明の発光素子においては発光層と電極の間にキャリア輸送層を形成することが好ましい。キャリア輸送層とは、陽極と発光層の間の陽極側キャリア輸送層、発光層と陽極の陰極側キャリア輸送層であり、電子や正孔のキャリア輸送の効率を高める役割をする。キャリア輸送層が存在することにより、発光層と電極が直接接続されるのではなく、伝導体である電極と半導体である発光層の間の電子やり取りを円滑にすることができる。
[Carrier transport layer]
In the light emitting device of the present invention, it is preferable to form a carrier transport layer between the light emitting layer and the electrode in the light emitting device of the present invention. The carrier transport layer is an anode-side carrier transport layer between the anode and the light-emitting layer, and a cathode-side carrier transport layer between the light-emitting layer and the anode, and plays a role of increasing the efficiency of carrier transport of electrons and holes. Due to the presence of the carrier transport layer, the light emitting layer and the electrode are not directly connected, but electronic exchange between the electrode serving as the conductor and the light emitting layer serving as the semiconductor can be facilitated.
用いる電極と発光層の種類により、陰極と発光層の間にのみキャリア輸送層を形成しても良く、また陽極と発光層の間にのみキャリア輸送層を形成しても良く、また両方のキャリア輸送層を形成しても良い。また、キャリア輸送層は各々一層でも構わず、キャリア移動を効率的に行おうとする際には各々二層以上にすることも好ましく行われる。キャリア輸送層の膜厚は特に限定されるものではないが、薄すぎるとキャリア輸送層として機能せず、厚過ぎると必要な電圧が高くなるため、好ましくは２０ｎｍ〜５μｍの範囲であり、より好ましくは５０ｎｍ〜３μｍの範囲である。 Depending on the type of electrode and light-emitting layer used, a carrier transport layer may be formed only between the cathode and the light-emitting layer, or a carrier transport layer may be formed only between the anode and the light-emitting layer. A transport layer may be formed. Further, each carrier transport layer may be a single layer, and preferably two or more layers are preferably used for efficient carrier movement. The film thickness of the carrier transport layer is not particularly limited, but if it is too thin, it will not function as a carrier transport layer, and if it is too thick, the necessary voltage will be high, so it is preferably in the range of 20 nm to 5 μm, more preferably. Is in the range of 50 nm to 3 μm.
キャリア輸送層は、各々正孔や電子を有効に輸送するために使われるため、陽極側キャリア輸送層はｐ型にドーピング、陰極側キャリア輸送層はｎ型にドーピングされ、伝導性が付与されていることが好ましい。キャリア輸送層の伝導度は高い方が抵抗が少なく有効にキャリアが移動する。そのため、伝導は高い方が好ましい。キャリア輸送層の抵抗が小さいことは、発光のために素子に印加する電圧低減にも繋がるのでより好ましい。
陽極側キャリア輸送層に用いる材料としては、イオン化エネルギーが低く、正孔注入が容易であるものが好ましく、例えばＮｉＯ、ＣｕＡｌＯ２、ｐ−ＧａＡｓ、ｐ-Ｓｉ等が挙げられる。また、陰極側キャリア輸送層に用いる材料としては、仕事関数が低く電子注入が容易であるものが好ましく、例えばＺｎＯ、ＺｎＳ、ＳｎＯ２等が挙げられる。
Since the carrier transport layer is used to effectively transport holes and electrons, the anode side carrier transport layer is doped p-type, the cathode side carrier transport layer is doped n-type, and conductivity is imparted. Preferably it is. The higher the conductivity of the carrier transport layer, the less the resistance, and the carriers move effectively. Therefore, higher conductivity is preferable. It is more preferable that the resistance of the carrier transport layer is small because it leads to a reduction in voltage applied to the element for light emission.
The material used for the anode-side carrier transport layer is preferably a material having low ionization energy and easy hole injection, such as NiO, CuAlO 2 , p-GaAs, and p-Si. Further, as a material used for the cathode-side carrier transporting layer is preferably a work function of facilitating the electron injection low, for example ZnO, ZnS, SnO 2 and the like.
[発光素子の製造方法]
本発明では、予め、発光層を形成する材料である無機化合物と、発光中心剤とを分散した溶液を作製して、それを第一の電極が形成された基板上に塗布し、その後加熱することにより、第一の電極上に発光層を形成することができる。そして、第一の電極上に形成された発光層に、第二の電極を形成することにより、発光素子を製造することができる。
第一の電極と第二の電極は異なる極性を持ち、各々陽極または陰極となるものである。 例えば、第一の電極が陽極であれば、第二の電極は陰極である。なお、陽極上に発光層を形成した後、陰極を形成してもよく、陰極上に発光層を形成したのち、陽極を形成してもよい。ただし、発光層で生じた発光を外部に取り出すため、少なくとも一方の電極が透明であることが必要である。なお電極に用いることの材料については上述した通りである。
[Method for manufacturing light-emitting element]
In the present invention, a solution in which an inorganic compound, which is a material for forming a light emitting layer, and a light emission centering agent are dispersed in advance is applied to the substrate on which the first electrode is formed, and then heated. Thus, the light emitting layer can be formed on the first electrode. And a light emitting element can be manufactured by forming a 2nd electrode in the light emitting layer formed on the 1st electrode.
The first electrode and the second electrode have different polarities, and each serves as an anode or a cathode. For example, if the first electrode is an anode, the second electrode is a cathode. In addition, after forming a light emitting layer on an anode, a cathode may be formed, and after forming a light emitting layer on a cathode, an anode may be formed. However, in order to extract light emitted from the light emitting layer to the outside, at least one of the electrodes needs to be transparent. The materials used for the electrodes are as described above.
本発明において第一の電極上に発光層を形成する方法としては、塗布、真空製膜法等の方法を用いることができる。塗布方法を用いる場合、まず、無機化合物と、発光中心剤とを分散した溶液を作成する。次に、それらを混合して異なる溶媒を入れて溶液から無機物を析出させることで、無機化合物に発光中心剤を付活させることができる。その後、発光中心剤が付活された無機化合物粒子を塗布する。ここで塗布方法としては、一般的な塗布方法を用いることができ、例えば、スピンコート等の方法を用いることができる。
そして、加熱することで発光層を形成することができる。加熱方法としては、所定の雰囲気中、例えば、Ａｒ、Ｘｅ、Ｎｅ、窒素等の不活性ガス中で熱処理を行う方法を挙げることができる。また、加熱することにより、２種類以上の無機化合物の構成元素を相互に拡散させることができる。さらに、発光中心剤の付活性を向上させることができる。
In the present invention, as a method for forming the light emitting layer on the first electrode, a method such as coating or vacuum film forming can be used. When using the coating method, first, a solution in which an inorganic compound and a luminescent center agent are dispersed is prepared. Next, the luminescent center agent can be activated in the inorganic compound by mixing them and adding a different solvent to precipitate an inorganic substance from the solution. Thereafter, inorganic compound particles in which the luminescent center agent is activated are applied. Here, as a coating method, a general coating method can be used, and for example, a method such as spin coating can be used.
Then, the light emitting layer can be formed by heating. Examples of the heating method include a method in which heat treatment is performed in a predetermined atmosphere, for example, in an inert gas such as Ar, Xe, Ne, or nitrogen. Moreover, the constituent element of two or more types of inorganic compounds can be mutually diffused by heating. Furthermore, the activity of the luminescent center agent can be improved.
ここで、2種類以上の無機化合物としては、―元系無機化合物や、二元系、三元系等の多元系無機化合物を用いることができる。二元系無機化合物としは、例えば、周期表第１３族元素と周期表第１５族元素との化合物と、周期表第１２族元素と周期表第１６族元素の化合物が好ましい。また、第一の電極が形成された基板上に金属の酢酸塩、アセチルアセトナト等の錯体を混合、溶媒に分散して塗布、その後、所定の雰囲気下加熱して酢酸塩や錯体を無機化する方法、及びこれらの方法の組み合わせによっても、発光層を形成することができる。 Here, as the two or more kinds of inorganic compounds, a binary inorganic compound or a multi-component inorganic compound such as a binary or ternary can be used. As the binary inorganic compound, for example, a compound of a periodic table group 13 element and a periodic table group 15 element, and a compound of a periodic table group 12 element and a periodic table group 16 element are preferable. Also, a metal acetate or acetylacetonate complex is mixed on the substrate on which the first electrode is formed, dispersed in a solvent, applied, and then heated in a specified atmosphere to mineralize the acetate or complex. The light emitting layer can also be formed by a method of performing the above and a combination of these methods.
真空製膜法を用いる場合、蒸着法、スパッタ法等の大面積の製膜が容易な方法を用いることが好ましい。また、無機化合物に必要な濃度の発光中心剤を添加した蒸着元もしくはスパッタターゲットを用いて、も良く、それぞれを別なソースとして共蒸着、共スパッタを行っても良い。また、２種類以上の無機化合物から、該化合物中の構成元素を相互に拡散させることで、ｐ型無機半導体粒子およびｎ型無機半導体粒子を形成させる場合は、それらの化合物を混合した蒸着元もしくはスパッタターゲットを用いても良く、それぞれを別なソースとして共蒸着、共スパッタを行っても良い。この場合は異なる材料を独立に制御できると言う観点で異なる蒸着元もしくはスパッタターゲットとして独立に印加するエネルギーを制御して所望の無機半導体粒子を形成させる方が好ましい。いずれの場合にも、基板に無機半導体粒子を含有する発光層が形成されるように、蒸着元もしくはスパッタターゲットの焼結度、印加する電子線やプラズマのエネルギー、基板温度等を調整して製膜する。ナノ粒子を形成するための条件は用いる材料に依存するので、場合によっては蒸着元もしくはスパッタターゲットは作製しようとする無機化合物の構成元素を含むアモルファスの状態も好ましく用いられる。 When using a vacuum film forming method, it is preferable to use a method that facilitates film formation of a large area, such as a vapor deposition method or a sputtering method. Alternatively, a vapor deposition source or a sputtering target to which an emission center agent having a concentration necessary for an inorganic compound is added may be used, and co-deposition and co-sputtering may be performed using each as a separate source. In addition, when p-type inorganic semiconductor particles and n-type inorganic semiconductor particles are formed by diffusing constituent elements in the compound from two or more kinds of inorganic compounds, a vapor deposition source in which those compounds are mixed or Sputter targets may be used, and co-evaporation and co-sputtering may be performed using each as a separate source. In this case, it is preferable to form the desired inorganic semiconductor particles by controlling the energy applied independently as a different vapor deposition source or sputtering target from the viewpoint that different materials can be controlled independently. In either case, the degree of sintering of the vapor deposition source or sputtering target, the energy of the applied electron beam or plasma, the substrate temperature, etc. are adjusted so that a light emitting layer containing inorganic semiconductor particles is formed on the substrate. Film. Since the conditions for forming the nanoparticles depend on the material used, in some cases, the deposition source or the sputter target is preferably used in an amorphous state containing the constituent element of the inorganic compound to be produced.
上述した方法で、第一の電極上に形成された発光層に、第二の電極を形成することにより、発光素子を製造することができる。第二の電極を設ける方法としては、例えば、真空蒸着等により、金属を蒸着させる方法を用いることができる。
また、必要に応じて、第一の電極と発光層の間、または第二の電極と発光層の間にキャリア輸送層を設けてもよい。キャリア輸送層を有する発光素子の製造方法としては、例えば、第一の電極上に、真空製膜によりキャリア輸送層、発光層、第二の電極等の必要な層を順次形成する方法、予めキャリア輸送層を形成する材料が分散した溶液や発光層を形成する粒子が分散した溶液を作製してそれを電極が形成された基板上に塗布する方法等が挙げられる。
A light emitting element can be manufactured by forming the second electrode on the light emitting layer formed on the first electrode by the method described above. As a method of providing the second electrode, for example, a method of depositing metal by vacuum deposition or the like can be used.
Moreover, you may provide a carrier transport layer between a 1st electrode and a light emitting layer or between a 2nd electrode and a light emitting layer as needed. Examples of a method for manufacturing a light-emitting element having a carrier transport layer include a method of sequentially forming necessary layers such as a carrier transport layer, a light-emitting layer, and a second electrode on a first electrode by vacuum film formation, Examples thereof include a method in which a solution in which a material for forming a transport layer is dispersed or a solution in which particles for forming a light emitting layer are dispersed is prepared and applied onto a substrate on which an electrode is formed.
以下に実施例により本発明を具体的に説明する。
[実施例１]
The present invention will be specifically described below with reference to examples.
[Example 1]
硝酸亜鉛６水和物２．２３１ｇ（７．５ｍｍｏｌ）、塩化テルビウム０．０１ｇ（０．０３８ｍｍｏｌ）を２５ｇの蒸留水に溶解した（溶液１）。また、硫化ナトリウム９水和物２．４ｇ（１０ｍｍｏｌ）を２５ｇの蒸留水に溶解した（溶液２）。同時にステンレス製のビーカーを用い、ヘプタン２１３ｇにC8H17COOCH2CH(COOC8H17)SO3Na ６１．７ｇを溶解したものを二つ作製した（溶液３）。次に、一つの溶液３に溶液１を加え、窒素雰囲気で、氷浴で冷却しながら超音波分散を行い、ミセル溶液（溶液４）を作製した。また、溶液３に溶液２を加え、窒素雰囲気で、氷浴で冷却しながら超音波分散を行い、ミセル溶液（溶液５）を作製した。次に窒素雰囲気で、氷浴で冷却しながら超音波分散を行いながら溶液４に溶液５を少しずつ入れ、１時間超音波分散処理を実施した。その後、エタノールを加え、溶液が白濁させ、遠心分離して沈殿を分離、上澄みを捨てて蒸留水を加えて再分散、遠心分離を繰り返して、界面活性剤を除去し、硫化亜鉛にテルビウムが付活された微粒子分散液を作製した。得られたナノ粒子の数平均粒径は２５ｎｍであった。 Zinc nitrate hexahydrate 2.231 g (7.5 mmol) and terbium chloride 0.01 g (0.038 mmol) were dissolved in 25 g of distilled water (solution 1). Further, 2.4 g (10 mmol) of sodium sulfide nonahydrate was dissolved in 25 g of distilled water (solution 2). At the same time, two stainless steel beakers were prepared by dissolving 61.7 g of C 8 H 17 COOCH 2 CH (COOC 8 H 17 ) SO 3 Na in 213 g of heptane (solution 3). Next, solution 1 was added to one solution 3, and ultrasonic dispersion was performed while cooling in an ice bath in a nitrogen atmosphere to prepare a micelle solution (solution 4). Further, the solution 2 was added to the solution 3, and ultrasonic dispersion was performed while cooling in an ice bath in a nitrogen atmosphere to prepare a micelle solution (solution 5). Next, the solution 5 was gradually added to the solution 4 while performing ultrasonic dispersion while cooling in an ice bath in a nitrogen atmosphere, and ultrasonic dispersion treatment was performed for 1 hour. After that, ethanol is added, the solution becomes cloudy, centrifuged to separate the precipitate, the supernatant is discarded, distilled water is added, redispersed and centrifuged repeatedly to remove the surfactant, and terbium is added to the zinc sulfide. An activated fine particle dispersion was prepared. The number average particle diameter of the obtained nanoparticles was 25 nm.
ＩＴＯ付きガラス基板をトルエンにて超音波洗浄し、さらにアセトンで超音波洗浄後、乾燥した。そのＩＴＯ電極上に、スピンコート１０００ｒｐｍで得られた微粒子分散液を塗布し、自然乾燥した。この工程を５回繰り返した後、Ａｒ雰囲気中５５０℃で５時間焼成して発光層を得た。次に、真空蒸着にて、真空度１.２×１０−５Ｔｏｒｒ以下、基板４０℃以下、蒸着速度１ｎｍ／秒で、マグネシウム層からなる陰極を形成し、発光素子とした。
得られた素子に直流電圧を印加したところ、５Vで３０ｍＡの電流が流れ、発光を示した。得られた発光は、発光層のみのフォトルミネッセンススペクトルとほぼ一致したことから、発光層に付活されたＴｂの発光であることが確認された。また、電圧を１０分印加し続けても発光は継続された。
[実施例２]
The glass substrate with ITO was ultrasonically cleaned with toluene, further ultrasonically cleaned with acetone, and then dried. On the ITO electrode, the fine particle dispersion obtained by spin coating at 1000 rpm was applied and dried naturally. This process was repeated 5 times, and then fired at 550 ° C. for 5 hours in an Ar atmosphere to obtain a light emitting layer. Next, by vacuum deposition, a cathode made of a magnesium layer was formed at a degree of vacuum of 1.2 × 10 −5 Torr or less, a substrate of 40 ° C. or less, and a deposition rate of 1 nm / second, to obtain a light emitting element.
When a direct current voltage was applied to the obtained device, a current of 30 mA flowed at 5 V, indicating light emission. Since the obtained luminescence almost coincided with the photoluminescence spectrum of only the luminescent layer, it was confirmed that the luminescence was Tb activated by the luminescent layer. Further, light emission continued even when the voltage was applied for 10 minutes.
[Example 2]
蒸留水２．０ｇにＮｉＣｌ２を１．０ｇ（７．７１ｍｏｌ）、ＬｉＣｌを０．０３ｇ（０．７７ｍｍｏｌ）溶解し、これに４．０ｇのエタノールを加えた。次に、HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20Hを２ｇ加えて２時間攪拌混合してＮｉＯ；Ｌｉの前駆体溶液を得た。得られた溶液をＩＴＯ付ガラス基板上に３００ｒｐｍで３秒、次に２０００ｒｐｍで１０秒スピンコートした後、大気中５００℃で３０分焼成して陽極と発光層の間のキャリア輸送層としてＮｉＯ；Ｌｉナノ粒子薄膜を得た。 In 2.0 g of distilled water, 1.0 g (7.71 mol) of NiCl 2 and 0.03 g (0.77 mmol) of LiCl were dissolved, and 4.0 g of ethanol was added thereto. Next, 2 g of HO (CH 2 CH 2 O) 20 (CH 2 CH (CH 3 ) O) 70 (CH 2 CH 2 O) 20 H was added and mixed with stirring for 2 hours to prepare a NiO; Li precursor solution. Obtained. The obtained solution was spin-coated on a glass substrate with ITO at 300 rpm for 3 seconds and then at 2000 rpm for 10 seconds, and then baked in the atmosphere at 500 ° C. for 30 minutes to form NiO as a carrier transport layer between the anode and the light-emitting layer; A Li nanoparticle thin film was obtained.
この上に実施例１と全く同様にして発光層、電極を形成して発光素子を作製した。得られた素子に直流電圧を印加したところ、５Vで３０ｍＡの電流が流れ、発光を示した。得られた発光は、発光層のみのフォトルミネッセンススペクトルとほぼ一致したことから、発光層に付活されたＴｂの発光であることが確認された。また、電圧を１０分印加し続けても発光は継続された。
[実施例３]
A light emitting layer and electrodes were formed thereon in the same manner as in Example 1 to produce a light emitting device. When a direct current voltage was applied to the obtained device, a current of 30 mA flowed at 5 V, indicating light emission. Since the obtained luminescence almost coincided with the photoluminescence spectrum of only the luminescent layer, it was confirmed that the luminescence was Tb activated by the luminescent layer. Further, light emission continued even when the voltage was applied for 10 minutes.
[Example 3]
エタノール（和光純薬製：特級）４５０ｍｌをホットスターラー上で攪拌及び加熱しながら、酢酸亜鉛２水和物（和光純薬製：特級）６．５８５ｇ（３０ｍｍｏｌ）と酢酸テルビウム４水和物（三津和化学製）０．５８８ｇ（１．４ｍｍｏｌ）を加え、還流しながら３時間混合した後に、冷蔵庫で冷却して亜鉛及びテルビウムを含む溶液を得た（溶液１）。また、水酸化リチウム１水和物１．７６２ｇ（４２ｍｍｏｌ）を１２０ｍｌのエタノールに溶解し、冷蔵庫で冷却してＬｉを含む溶液（溶液２）を得た。次に、氷浴中で超音波分散を行いながら、溶液１に溶液２をゆっくり加えて、２０分間超音波分散させて加水分解し、反応液を得た（溶液３）。溶液３を冷蔵庫中で１週間静置して、発光中心剤としてテルビウムが付活された酸化亜鉛のナノ結晶を成長させ、ナノ結晶を含む溶液（溶液４）を得た。溶液４１１０ｇに対してヘプタンを１８０ｇの割合で加えて析出させ、遠心分離して上澄みを捨て、再度エタノールを加えて分散、ヘプタンを加えて析出、遠心分離という洗浄操作を２回繰り返し、副生成物を除去した。これらにより、酸化亜鉛結晶微粒子７．５ｔ％含有するエタノール溶液とし、超音波分散して塗布溶液とした（溶液５）。得られた結晶ナノ粒子の数平均粒径は、約５〜６ｎｍであった。 While stirring and heating 450 ml of ethanol (made by Wako Pure Chemical: Special Grade) on a hot stirrer, 6.585 g (30 mmol) of zinc acetate dihydrate (made by Wako Pure Chemical: Special Grade) and terbium acetate tetrahydrate (Mitsu) 0.588 g (1.4 mmol) (manufactured by Wa Kagaku) was added and mixed for 3 hours under reflux, and then cooled in a refrigerator to obtain a solution containing zinc and terbium (solution 1). Further, 1.762 g (42 mmol) of lithium hydroxide monohydrate was dissolved in 120 ml of ethanol and cooled in a refrigerator to obtain a solution containing Li (solution 2). Next, while ultrasonically dispersing in an ice bath, the solution 2 was slowly added to the solution 1, and ultrasonically dispersed for 20 minutes for hydrolysis to obtain a reaction solution (solution 3). The solution 3 was allowed to stand in a refrigerator for 1 week to grow terbium-activated zinc oxide nanocrystals as a luminescent center agent to obtain a solution (solution 4) containing nanocrystals. 180 g of heptane was added to 4110 g of the solution to precipitate, centrifuged, the supernatant was discarded, ethanol was added again to disperse, and the washing operation of adding heptane to precipitation and centrifugation was repeated twice to produce a by-product Was removed. Thus, an ethanol solution containing 7.5 t% of zinc oxide crystal particles was ultrasonically dispersed to obtain a coating solution (solution 5). The number average particle diameter of the obtained crystal nanoparticles was about 5 to 6 nm.
市販のＧａｎ粉末を購入して微粉砕し、数平均粒径３０ｎｍ程度のＧａＮ粒子を得て、それを溶液５にＺｎＯ：ＧａＮがモル比で１：１になるように加えてＺｎＯとＧａＮを含有する微粒子分散液を得た。
ＩＴＯ付きガラス基板をトルエンにて超音波洗浄し、さらにアセトンで超音波洗浄後、乾燥した。そのＩＴＯ電極上に、スピンコート１０００ｒｐｍで得られた微粒子分散液を塗布し、自然乾燥した。この工程を５回繰り返した後、Ａｒ雰囲気中５５０℃で５時間焼成して発光層を得た。次に、真空蒸着にて、真空度１.２×１０−５Ｔｏｒｒ以下、基板４０℃以下、蒸着速度１ｎｍ／秒で、アルミニウム層からなる陰極を形成し、発光素子とした。
Commercially available Gan powder is purchased and finely pulverized to obtain GaN particles having a number average particle size of about 30 nm, and ZnO and GaN are added to Solution 5 so that the molar ratio of ZnO: GaN is 1: 1. A fine particle dispersion containing was obtained.
The glass substrate with ITO was ultrasonically cleaned with toluene, further ultrasonically cleaned with acetone, and then dried. On the ITO electrode, the fine particle dispersion obtained by spin coating at 1000 rpm was applied and dried naturally. This process was repeated 5 times, and then fired at 550 ° C. for 5 hours in an Ar atmosphere to obtain a light emitting layer. Next, by vacuum deposition, a cathode made of an aluminum layer was formed at a vacuum degree of 1.2 × 10 −5 Torr or less, a substrate of 40 ° C. or less, and a deposition rate of 1 nm / second, to obtain a light emitting element.
得られた素子に直流電圧を印加したところ、５Vで３０ｍＡの電流が流れ、発光を示した。得られた発光は、発光層のみのフォトルミネッセンススペクトルとほぼ一致したことから、発光層に付活されたＴｂの発光であることが確認された。また、電圧を１０分印加し続けても発光は継続された。
[実施例４]
When a direct current voltage was applied to the obtained device, a current of 30 mA flowed at 5 V, indicating light emission. Since the obtained luminescence almost coincided with the photoluminescence spectrum of only the luminescent layer, it was confirmed that the luminescence was Tb activated by the luminescent layer. Further, light emission continued even when the voltage was applied for 10 minutes.
[Example 4]
蒸留水２．０ｇにＮｉＣｌ２を１．０ｇ（７．７１ｍｏｌ）、ＬｉＣｌを０．０３ｇ（０．７７ｍｍｏｌ）溶解し、これに４．０ｇのエタノールを加えた。次に、HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20Hを２ｇ加えて２時間攪拌混合してＮｉＯ；Ｌｉの前駆体溶液を得た。得られた前駆体溶液をＩＴＯ付ガラス基板上に３００ｒｐｍで３秒、次に２０００ｒｐｍで１０秒スピンコートした後、大気中５００℃で３０分焼成して陽極と発光層の間のキャリア輸送層としてＮｉＯ；Ｌｉナノ粒子薄膜を得た。この上に実施例３と全く同様にして発光層、電極を形成して発光素子を作製した。 In 2.0 g of distilled water, 1.0 g (7.71 mol) of NiCl 2 and 0.03 g (0.77 mmol) of LiCl were dissolved, and 4.0 g of ethanol was added thereto. Next, 2 g of HO (CH 2 CH 2 O) 20 (CH 2 CH (CH 3 ) O) 70 (CH 2 CH 2 O) 20 H was added and mixed with stirring for 2 hours to prepare a NiO; Li precursor solution. Obtained. The obtained precursor solution was spin-coated on a glass substrate with ITO at 300 rpm for 3 seconds and then at 2000 rpm for 10 seconds, and then baked in air at 500 ° C. for 30 minutes to form a carrier transport layer between the anode and the light-emitting layer. A NiO; Li nanoparticle thin film was obtained. A light emitting layer and electrodes were formed thereon in the same manner as in Example 3 to produce a light emitting device.
得られた素子に直流電圧を印加したところ、５Vで３０ｍＡの電流が流れ、発光を示した。得られた発光は、発光層のみのフォトルミネッセンススペクトルとほぼ一致したことから、発光層に付活されたＴｂの発光であることが確認された。また、電圧を１０分印加し続けても発光は継続された。
[比較例１]
When a direct current voltage was applied to the obtained device, a current of 30 mA flowed at 5 V, indicating light emission. Since the obtained luminescence almost coincided with the photoluminescence spectrum of only the luminescent layer, it was confirmed that the luminescence was Tb activated by the luminescent layer. Further, light emission continued even when the voltage was applied for 10 minutes.
[Comparative Example 1]
実施例１におけるＺｎＳナノ粒子作製に際し、実施例１では〔Ｈ２Ｏ〕／［C8H17COOCH2CH(COOC8H17)SO3Na］＝１０であったところを、水を多く加えて１００としたこと以外は実施例１と同様にして発光素子を作製した。得られたＺｎＳ粒子の数平均粒径は１５０ｎｍであった。得られた素子に直流電圧を印加したところ、５Vで３０ｍＡの電流が流れ、発光を示したものの、発光輝度が低く、実施例に比べて、発光効率も低いものであった。また、初期に発光を観測したが電圧を印加して１分程度で絶縁破壊が起き、発光は継続しなかった。 In preparing the ZnS nanoparticles in Example 1, in Example 1, [H 2 O] / [C 8 H 17 COOCH 2 CH (COOC 8 H 17 ) SO 3 Na] = 10 was added. A light emitting device was fabricated in the same manner as in Example 1 except that the number was 100. The number average particle diameter of the obtained ZnS particles was 150 nm. When a direct current voltage was applied to the obtained device, a current of 30 mA flowed at 5 V and light emission was exhibited, but the light emission luminance was low and the light emission efficiency was low as compared with the Examples. In addition, light emission was observed in the initial stage, but dielectric breakdown occurred in about 1 minute after voltage application, and light emission did not continue.
本発明の発光素子は、ガラス基板等の安価な基板上に形成できるために大面積化が容易でありながら、直流低電圧で駆動できるために発光効率に優れ、粒径が小さく、絶縁破壊を起こしにくいため寿命が長く、全て無機材料から構成できるために耐久性に優れるために実用的であり、ＬＣＤバックライトや一般照明の非水銀化に大きく貢献する。 The light-emitting element of the present invention can be formed on an inexpensive substrate such as a glass substrate, so that it is easy to increase the area, but it can be driven with a direct current low voltage, so it has excellent luminous efficiency, small particle size, and dielectric breakdown. It is difficult to cause long life, and since it can be made of all inorganic materials, it is practical because of its excellent durability, and greatly contributes to non-mercury of LCD backlights and general lighting.
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Cited By (5)
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| JP2009193962A (en) * | 2008-02-13 | 2009-08-27 | Samsung Mobile Display Co Ltd | Electrode, its manufacturing method, and electron element equipped with the electrode |
| JP2009221469A (en) * | 2008-02-21 | 2009-10-01 | Semiconductor Energy Lab Co Ltd | Method for manufacturing inorganic electroluminescent blue-light emitting body, inorganic electroluminescent blue-light emitting body, and light-emitting device |
| CN102194908A (en) * | 2010-03-03 | 2011-09-21 | 株式会社日立制作所 | Sealing material plate with wavelength conversion material and solar battery with the same |
| JP2017014476A (en) * | 2015-07-03 | 2017-01-19 | 国立大学法人名古屋大学 | Tellurium compound nanoparticle and composite nanoparticle and manufacturing method therefor |
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| JP2009193962A (en) * | 2008-02-13 | 2009-08-27 | Samsung Mobile Display Co Ltd | Electrode, its manufacturing method, and electron element equipped with the electrode |
| JP2009221469A (en) * | 2008-02-21 | 2009-10-01 | Semiconductor Energy Lab Co Ltd | Method for manufacturing inorganic electroluminescent blue-light emitting body, inorganic electroluminescent blue-light emitting body, and light-emitting device |
| CN102194908A (en) * | 2010-03-03 | 2011-09-21 | 株式会社日立制作所 | Sealing material plate with wavelength conversion material and solar battery with the same |
| JP2017014476A (en) * | 2015-07-03 | 2017-01-19 | 国立大学法人名古屋大学 | Tellurium compound nanoparticle and composite nanoparticle and manufacturing method therefor |
| KR20170105156A (en) * | 2016-03-08 | 2017-09-19 | 삼성디스플레이 주식회사 | Light emitting device and method for preparing the same |
| KR102527228B1 (en) * | 2016-03-08 | 2023-05-02 | 삼성디스플레이 주식회사 | Light emitting device and method for preparing the same |
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