1304305 九、發明說明： 【發明所屬之技術領域】 本發明提供一種有機電激發光元件，尤指一種具有一設於陰極 内之緩衝層的有機電激發光元件。 【先前技術】 在各種形式平面顯示器中，由於有機電激發光顯示器 鲁 （organic electroluminescent display，OLED )具有很多有 利特點，例如自發光源、視角廣、響應時間快、色彩豐富、 構造簡單以及節省能源等好處，因此有機電激發光顯示器 已被廣泛使用於中小尺寸之攜帶型顯示器領域中。 一有機電激發光顯示器係由很多個包含有有機電激發 光材料之有機電激發光元件所形成。美國專利案號第 φ 6,548,956號揭露了一雙面發光彩色顯示器之有機電激發光 元件，其具有垂直堆疊之材料層。請參考第1圖，第1圖 為根據習知美國專利案號第6,548,956號之一有機電激發 光元件的側剖面示意圖。有機電激發光元件1〇〇係形成於 一玻璃基底102上，其表面已預先塗佈有一透明氧化銦錫 (indium tin oxide，ITO)薄膜1〇4。膜層106包含電洞引 導化合物（hole conducting compound)，而膜層108包含電 子引導以及高電激發光材料，其中膜層1〇6、1〇8係由有機 材料所組成。膜層110提供給有機電激發光元件1〇〇 一電 1304305 子注入接觸端，其係藉由沉積方式所製作，且由金屬材料 形成，包含有一層薄半透明鎂（magnesium，Mg)/銀（silver ’ Ag)合金電極。頂層112係為一厚ITO膜或一厚氧化銦鋅 (indium zinc oxide，ΙΖ0)膜。數字標號 114 以及 116 表 示電極接觸端。IT0薄膜104係用來當作陽極，而頂層112 以及薄金屬層110係用來當作有機電激發光元件100的陰 極0 為了能注入電子，薄金屬層110的功函數必須能與膜層 108中之有機材料的最低能量空軌道（lowest unoccupied molecular orbital，LUMO)之能階相匹配。另一方面，由 於有機電激發光元件100係為一雙面發光彩色顯示器，所 以頂層112以及薄金屬層110必須為透明的，也因此薄金 屬層110必須非常薄，因而造成較差之導電性，所以必須 以具有透明導電材料ITO或IZO之頂層112來補償陰極的 電性。然而，以ITO或IZO或形成的透明頂層1丨2係以濺 鍍沉積方式形成於薄金屬層110的鎂/銀合金表面，由於電 子與離子會於濺鍍製程中轟擊下方材料，因此容易傷害薄 金屬層110以及膜層106、108内的有機材料。此等傷害會 造成低發光效率以及降低有機電激發光元件之壽命。因 此，上述揭露技術的缺點之一即為有機電激發光元件的發 光效率和壽命會被降低。 61304305 IX. Description of the Invention: [Technical Field] The present invention provides an organic electroluminescent device, and more particularly to an organic electroluminescent device having a buffer layer provided in a cathode. [Prior Art] In various forms of flat panel displays, organic electroluminescent display (OLED) has many advantageous features, such as self-illuminating source, wide viewing angle, fast response time, rich colors, simple structure, and energy saving. The advantage is that organic electroluminescent display has been widely used in the field of small and medium-sized portable displays. An organic electroluminescent display is formed from a plurality of organic electroluminescent elements comprising an organic electroluminescent material. U.S. Patent No. 6,548,956 discloses an organic electroluminescent device of a double-sided illuminated color display having a vertically stacked layer of material. Referring to Fig. 1, there is shown a side cross-sectional view of an organic electroluminescent device according to the conventional U.S. Patent No. 6,548,956. The organic electroluminescent device 1 is formed on a glass substrate 102 having a surface coated with a transparent indium tin oxide (ITO) film 1〇4. The film layer 106 comprises a hole conducting compound, and the film layer 108 comprises an electron guiding and a high electrical excitation light material, wherein the film layers 〇6, 1〇8 are composed of an organic material. The film layer 110 is provided to the organic electroluminescent device 1 by using a deposition method, which is formed by a deposition method and is formed of a metal material and contains a thin translucent magnesium (magnesium, Mg)/silver (silver 'Ag) alloy electrode. The top layer 112 is a thick ITO film or a thick indium zinc oxide (ITO) film. Numerals 114 and 116 denote electrode contact ends. The IT0 film 104 is used as an anode, and the top layer 112 and the thin metal layer 110 are used as the cathode of the organic electroluminescent device 100. In order to be able to inject electrons, the work function of the thin metal layer 110 must be compatible with the film layer 108. The energy level of the lowest energy unoccupied molecular orbital (LUMO) of the organic material is matched. On the other hand, since the organic electroluminescent device 100 is a double-sided illuminated color display, the top layer 112 and the thin metal layer 110 must be transparent, and therefore the thin metal layer 110 must be very thin, thereby causing poor conductivity. Therefore, the electrical properties of the cathode must be compensated for by the top layer 112 having a transparent conductive material ITO or IZO. However, the transparent top layer 1 丨 2 formed by ITO or IZO or the like is formed on the surface of the magnesium/silver alloy of the thin metal layer 110 by sputtering deposition. Since electrons and ions bombard the underlying material in the sputtering process, it is easy to be damaged. The thin metal layer 110 and the organic materials in the film layers 106, 108. Such damage can result in low luminous efficiency and a reduction in the life of the organic electroluminescent device. Therefore, one of the disadvantages of the above disclosed technique is that the light-emitting efficiency and lifetime of the organic electroluminescent device are lowered. 6
V 1304305 ^ 有關有機電激發光元件之另一構想係揭露於美國專利 案號第6,420,031號，由Parthasarathy等人所提出。第2 圖為Parthasarathy專利所揭露一透明發光顯示器（TOLED ) 200的剖面示意圖。透明發光顯示器包含有一非金屬陰極 202、一電子注入接合層（electron injecting interface layer， EIL ) 204、一電子傳輸層（electron transporting layer，ETL ) 206、一電洞傳輸層（hole transporting layer，HTL ) 208、 • 一陽極層21〇以及一基底212。電子注入接合層204的製 作是在沉積完電洞傳輸層208以及電子傳輸層206之後， 再藉由沉積一層菁銅（COpper phthalocyanine，CuPc )薄膜 而形成，電子注入接合層204係被之後以濺鍍方式形成的 IT0膜所覆蓋，此IT〇層係用來當作toleD 200的陰極 202 〇 然而’菁銅材料會吸收波長約為625奈米之光線，因此 會對光線效率造成影響。此外，在接近陰極處使用菁銅會 造成較南操作電壓。再者，菁銅的蒸鍍溫度遠高於一般有 機材料’且因菁銅材料較不易清洗，所以容易在製作菁銅 層時造成療鍍腔體之污染。因此，具有菁銅材料的透明發 光顯示器200並不適合用於量產。 由上il 了 4 如何提供具有較佳發光效率且易於量產之 有機％激發光元件仍然為業界之重要課題之一。 1304305 【發明内容】 本發明提供一種包含有一有機電激發光元件之電子裝 置，以用來顯示影像。上述有機電激發光元件之一實施例 包含有一陽極、一有機電激發光材料層以及一複合層透明 陰極依序設於一基底上。該透明陰極包含有一薄金屬層設 於透明陰極之底部、一摻雜緩衝層設於薄金屬層之上，以 及一透明電極設於摻雜緩衝層之上。 該摻雜緩衝層提供了保護薄金屬層及其下方材料之功 能，而且即使透明電極材料具有一低功函數，其仍然能維 持電子注入效率。因此，本發明之一實施例提供了一頂部 發光或一雙面發光有機電激發光顯示器，其包含有具較佳 發光效率與較長壽命之有機電激發光元。 【實施方式】 第3圖為本發明用於顯示影像之一電子裝置之一實施例 的頂視圖。如第3圖所示，電子裝置1包含有一輸入元件 15以及一有機電激發光顯示器10。電子裝置1可為一攜帶 式裝置，例如個人數位助理（personal digital assistant， PDA)、筆記型電腦、平板電腦、手機或影像顯示監視器等。 輸入元件15可耦合至有機電激發光顯示器10且包含有一 處理器或類似元件，以提供影像資料給一控制電路14，進 而產生影像。有機電激發光顯示器10包含有一顯示區域 8 1304305 數條掃線22 (例如1 D2及D3)與複 區域12亦包含有複數二組列。顯示 路26具有至纟―^ 像素電路26，其巾各次像素電 LV ^ 4 膜電晶體（thin film transistor，TFT ) 以及一有機電激發 Μ的各交界處。各；；=設於1料線22與-掃描線 像素電路26係電連接於對應之一資 電广掃(線24 ’以驅動所對應之次像素内的有機 後驅:、70件2G。資料線m、D2及D3係連接於一資料 =動器⑷用來接收一影像資料訊號，而掃描線S1、S2 m接於掃插線驅動器18，用來接收一開關/定址訊 T描線驅動器18與資料線驅動器16係藉由—控制電 路1/所控制。有機電激發光顯示ϋ 10可為-頂部發光顯 不杰’然而本發明亦可應用於一雙面發光顯示器。 第4圖為第3圖所示有機電激發光元件2〇的側剖面示 意圖。如第4圖所示，有機電激發光元件2〇包含有一基底 27以及一陽極29、一電洞注入層31、一電洞傳輸層（h〇le injection layer，HIL) 28、一發光層（emitting layer，EML) 30、一電子傳輸層32、一電子注入層34與一複合層透明 陰極42依序設於基底27上。有機電激發光顯示器1〇可 為一頂部發光顯示器，其中基底27以及陽極29電極可皆 為透明的。在本實施例中，基底27可為一坡螭基底。在不 同的貫施例中，基底可為一塑膠薄板或金屬薄板。陽極29 1304305 .可& ITO AIZO所形成。然而，在其他實施例中，當陽極 29不品為透明日守’其可由金（auruin，Au )、銀、紹 ‘ （aluminum，A1)或鉑（piatinum，ρ〇 所形成。V 1304305 ^ Another idea for an organic electroluminescent device is disclosed in U.S. Patent No. 6,420,031, to the name of Parthasarathy et al. Figure 2 is a cross-sectional view of a transparent light emitting display (TOLED) 200 disclosed in the Parthasarathy patent. The transparent light emitting display comprises a non-metal cathode 202, an electron injecting interface layer (EIL) 204, an electron transporting layer (ETL) 206, and a hole transporting layer (HTL). 208, • an anode layer 21〇 and a substrate 212. The electron injection bonding layer 204 is formed by depositing a layer of a copper phthalocyanine (CuPc) film after depositing the hole transport layer 208 and the electron transport layer 206, and the electron injection bonding layer 204 is then sputtered. Covered by the IKO film formed by the plating method, this IT layer is used as the cathode 202 of the toleD 200. However, the 'cyanate material absorbs light having a wavelength of about 625 nm, thus affecting the light efficiency. In addition, the use of copper bronze near the cathode results in a souther operating voltage. Further, the vapor deposition temperature of the cyanine copper is much higher than that of the general organic material, and since the cyanine copper material is less likely to be cleaned, it is easy to cause contamination of the plating chamber when the cyanine layer is produced. Therefore, the transparent light-emitting display 200 having a cyanine material is not suitable for mass production. From il 4 How to provide organic % excitation light elements with better luminous efficiency and easy mass production is still one of the important topics in the industry. 1304305 SUMMARY OF THE INVENTION The present invention provides an electronic device including an organic electroluminescent device for displaying an image. An embodiment of the above organic electroluminescent device comprises an anode, an organic electroluminescent material layer and a composite transparent cathode sequentially disposed on a substrate. The transparent cathode comprises a thin metal layer disposed on the bottom of the transparent cathode, a doped buffer layer disposed on the thin metal layer, and a transparent electrode disposed on the doped buffer layer. The doped buffer layer provides the function of protecting the thin metal layer and the material underneath, and maintains electron injection efficiency even if the transparent electrode material has a low work function. Accordingly, an embodiment of the present invention provides a top-emitting or double-sided illuminated organic electroluminescent display comprising organic electroluminescent elements having better luminous efficiency and longer lifetime. [Embodiment] Fig. 3 is a top plan view showing an embodiment of an electronic device for displaying an image of the present invention. As shown in Fig. 3, the electronic device 1 includes an input member 15 and an organic electroluminescent display 10. The electronic device 1 can be a portable device such as a personal digital assistant (PDA), a notebook computer, a tablet computer, a mobile phone or an image display monitor. Input component 15 can be coupled to organic electroluminescent display 10 and includes a processor or similar component to provide image data to a control circuit 14 for image generation. The organic electroluminescent display 10 includes a display area 8 1304305. The plurality of wipers 22 (e.g., 1 D2 and D3) and the complex region 12 also include a plurality of sets of columns. The display circuit 26 has a pixel circuit 26 to the respective corners of the sub-pixel LV ^ 4 thin film transistor (TFT) and an organic electro-excitation Μ. Each of the feed lines 22 and the scan line pixel circuits 26 is electrically connected to a corresponding organic power sweep (line 24' to drive the organic rear drive in the corresponding sub-pixel: 70 pieces of 2G. The data lines m, D2 and D3 are connected to a data converter (4) for receiving an image data signal, and the scan lines S1, S2 m are connected to the sweep line driver 18 for receiving a switch/addressing T-line driver. 18 and the data line driver 16 are controlled by the control circuit 1. The organic electroluminescence display ϋ 10 can be - the top emission is not good. However, the present invention can also be applied to a double-sided light-emitting display. A side cross-sectional view of the organic electroluminescent device 2A shown in Fig. 3. As shown in Fig. 4, the organic electroluminescent device 2 includes a substrate 27 and an anode 29, a hole injection layer 31, and a hole. A transfer layer (HIL) 28, an emission layer (EML) 30, an electron transport layer 32, an electron injection layer 34, and a composite transparent cathode 42 are sequentially disposed on the substrate 27. The organic electroluminescent display 1 can be a top-emitting display, wherein the substrate 27 And the anode 29 electrode can be transparent. In this embodiment, the substrate 27 can be a sloping substrate. In different embodiments, the substrate can be a plastic sheet or a metal sheet. The anode 29 1304305 can be & ITO AIZO is formed. However, in other embodiments, when the anode 29 is not transparent, it may be formed of gold (auruin, Au), silver, aluminum (A1) or platinum (piatinum, ρ〇). .
電洞注入層31、電洞傳輸層28、發光層30、電子傳輸 層32以及電子注入層34組成一有機電激發光材料層，且 發光層30可為摻雜材料的發光層，其中該掺質濃度為約 _ 0·01至10重量百分比。電洞注入層31的主要材料為LGThe hole injection layer 31, the hole transport layer 28, the light emitting layer 30, the electron transport layer 32, and the electron injection layer 34 constitute an organic electroluminescent material layer, and the light emitting layer 30 may be a light emitting layer of a doping material, wherein the doping The concentration is about _0·01 to 10% by weight. The main material of the hole injection layer 31 is LG.
化學公司（LGChem)所生產的LGC101⑧。電洞傳輸層28 包含有NPB (4,4、bis[N-( 1-naphthyl)-N-phenylamino]biphenyl)。發光 層30包含有8-羥基喹啉鋁LGC1018 produced by the chemical company (LGChem). The hole transport layer 28 contains NPB (4,4, bis[N-(1-naphthyl)-N-phenylamino]biphenyl). The luminescent layer 30 comprises 8-hydroxyquinoline aluminum
(tris(8-quinolinato_Nl，08)_aluminum，Alq3 )，其摻雜有 C545T (10_(2_benzothiazolyl)-2,3,6,7_tetrahydro_l，l，7,7，_tetramet ® hyl-M-H，5H,llH-[l]BENZOPYRANO[6,7,8-ij]quionlizin-l 卜one)。電子傳輸層32包含有Alq3，同時電子注入層34 包含有氟化鐘（lithium fluoride，LiF )。上述各層有機電 激發光材料可分別藉由蒸鑛（evaporation)、旋轉塗佈（spin coating)或喷墨（ink jet printing)等方式形成於陽極29 上。在各種實施例中，包含有機電激發光材料的膜層係由 真空蒸鍍法、分子線蒸鍵法（evaporation on molecular beam epitaxy，MBE)、沈浸法、旋轉塗佈法、鑄造法、條碼法 1304305 (barC°d〇M滚筒塗佈法㈤U_ing)所形成 複合層透明陰極“ 雜緩衝層38以及、 糸由一薄金屬層36、一摻 由-蒸鑛法所势透明電極40所構成。薄金屬層36可藉 Ba)、舞（广’且選擇性包含有銘、銀、鋇（barium，(tris(8-quinolinato_Nl,08)_aluminum,Alq3) doped with C545T (10_(2_benzothiazolyl)-2,3,6,7_tetrahydro_l,l,7,7,_tetramet ® hyl-MH,5H,llH-[ l] BENZOPYRANO [6,7,8-ij]quionlizin-l 卜one). The electron transport layer 32 contains Alq3 while the electron injection layer 34 contains a lithium fluoride (LiF). Each of the above layers of the organic electroluminescent material may be formed on the anode 29 by evaporation, spin coating or ink jet printing, respectively. In various embodiments, the film layer comprising the organic electroluminescent material is a vacuum evaporation method, an evaporation on molecular beam epitaxy (MBE), an immersion method, a spin coating method, a casting method, a barcode method. 1304305 (barC°d 〇M roller coating method (5) U_ing) formed of a composite layer transparent cathode "heterobuffer layer 38 and 糸 is composed of a thin metal layer 36, a doping-vaporization method potential transparent electrode 40. Thin The metal layer 36 can be borrowed from Ba), dance (wide) and optionally contains Ming, Silver, and Barium (barium,
#〇 〃或上述金屬材料之合金。為了使 於或ΐ於^1’第4圖中所示之薄金屬層36的厚度h可小 aH、，奈米。在—實施例中’薄金屬層的厚度範圍可 二”不、米至20奈米。摻雜緩衝層38包含有電子傳輸材 ’且摻雜有低功函數摻f，其中該電子傳輸材料可為鄭 或1 〇祕笨並啥琳鈹（bis(J 0-hydr〇xyben-z响㈣⑽_〇) beryllium，Bebq2 )。摻雜緩衝層3 8可藉由共蒸鍵方式所形#〇 〃 or an alloy of the above metal materials. The thickness h of the thin metal layer 36 shown in Fig. 4 may be small or small, nanometer. In the embodiment, the thickness of the thin metal layer may range from two to 20 nanometers. The doping buffer layer 38 includes an electron transporting material 'and is doped with a low work function doping f, wherein the electron transporting material may For Zheng or 1 〇 笨 啥 啥 bis bis (bis (J 0-hydr〇xyben-z ring (four) (10) _ 〇) beryllium, Bebq2). Doping buffer layer 38 can be formed by co-evaporation
成。摻雜緩衝層38的摻質包含有具低功函數的金屬材料， 其中該低功函數可小於或等於4·2電子伏特（dectr〇n v〇h， eV)。在一實施例中，摻質的金屬材料包含有鹼金屬（alkaH metal )、驗 土金屬（alkali earth metals )、過渡金屬或稀土 金屬（rare earth metal)。根據不同的實施例，該摻質的金 屬材料可選自鋰、鉋（cesium，Cs )、銷（strontium，Sr ) 或釤（samarium，Sm)。摻雜缓衝層38中金屬材料的摻質 濃度可為約0· 1至99重量百分比。在一實施例中，摻質濃 度可為約0.1至30重量百分比。摻雜緩衝層38的厚度可 為約1奈米至50奈米。在形成摻雜緩衝層38之後，可以 11 1304305 . 濺鍍製程形成一透明電極40,其中透明電極4〇包含有IT〇 • 或ΙΖΟ，且厚度為約10奈米矣400奈米。摻雜緩衝層％ 可以避免薄金屬層36以及位於薄金屬層36下方的有機電 機發光材料在以濺鍍製程製作透明電極4〇時受到傷宝。此 外，由於摻雜緩衝層38中的電子傳輸材料摻雜有低功函數 材料’能具有高電子注入以及傳輸效率’因此即使透明電 極40的材料具有高功函數，有機電激發光元件2〇仍然能 鲁 具有南電子注入效率。 根據不同的實施例，本發明提供了一種有機電激發光元 件，其具有包含了 一摻雜緩衝層之複合層透明陰極。Χ有機 電激發光元件可以應用於有機電激發先顯示器或任何電子 裝置：二由於包含有前文所揭露之特殊材料，摻雜緩衝層 能保護薄金屬層以及其下方的有機材料，而不會損失電^ φ注入與傳輸效率，而且該薄金屬層可被保留於陰極中，以 匹配其下方有機材料的LUM〇能階，使得此發光元件能具 有一較佳發光效率。因此，本發明能提供一種具有較長壽 7以及車乂佳顯不效果的頂部發光或雙面發光有機電激 元件或有機電激發光顯示器。 以上所述僅為本發明之較佳實酬，凡依本發财請專利 圍所做之解變化與㈣，皆闕本發日狀涵蓋範圍。 1304305 【圖式簡單說明】 第1圖為習知一有機電激發光元件的側剖面示意圖。 第2圖為習知一透明發光顯示器的剖面示意圖。 第3圖為本發明用於顯示影像之一電子裝置之一實施例的 頂視圖。 第4圖為第3圖所示有機電激發光元件的側剖面示意圖。 【主要元件符號說明】 1 電子裝置 10 有機電激發光顯示器 12 顳示區域 14 控制電路 15 輸入元件 16 貧料線驅動為 18 掃描線驅動器 20 有機電激發光元件 22 資料線 24 掃描線 26 次像素電路 27 基底· 28 電洞傳輸層 29 陽極 30 發光層 31 電洞注入層 32 電子傳輸層 34 電子注入層 36 薄金屬層 38 摻雜缓衝層 40 透明電極 42 透明陰極 100 有機電激發光元件 102 玻璃基底 104、 106 、 108 、 110 薄膜 112 頂層 114、 116 電極接觸端 200 透明發光顯示器 202 陰極 13 1304305 204 電子注入接合層 206 電子傳輸層 208 電洞傳輸層 210 陽極層 212 基底to make. The dopant of the doped buffer layer 38 comprises a metal material having a low work function, wherein the low work function can be less than or equal to 4·2 electron volts (dectr〇n v〇h, eV). In one embodiment, the dopant metal material comprises an alkali metal (alkaH metal), an alkali earth metal, a transition metal or a rare earth metal. According to various embodiments, the dopant metal material may be selected from the group consisting of lithium, cesium (Cs), strontium (Sr) or samarium (Sm). The dopant concentration of the metal material in the doped buffer layer 38 may range from about 0.1 to 99 weight percent. In one embodiment, the dopant concentration can be from about 0.1 to 30 weight percent. The doped buffer layer 38 may have a thickness of from about 1 nm to about 50 nm. After the doping buffer layer 38 is formed, a transparent electrode 40 may be formed by a sputtering process, wherein the transparent electrode 4 includes IT〇 or ΙΖΟ and has a thickness of about 10 nm to 400 nm. The doping buffer layer % can prevent the thin metal layer 36 and the organic motor luminescent material located under the thin metal layer 36 from being damaged when the transparent electrode 4 is formed by a sputtering process. In addition, since the electron transporting material in the doping buffer layer 38 is doped with a low work function material 'can have high electron injecting and transport efficiency', even if the material of the transparent electrode 40 has a high work function, the organic electroluminescent element 2 is still Nenglu has the efficiency of South electron injection. According to various embodiments, the present invention provides an organic electroluminescent device having a composite layer transparent cathode comprising a doped buffer layer. ΧOrganic electroluminescent elements can be applied to organic electro-acoustic prior displays or any electronic device: Second, due to the inclusion of the special materials disclosed above, the doped buffer layer protects the thin metal layer and the organic material underneath it without loss. The φ φ injection and transmission efficiency, and the thin metal layer can be retained in the cathode to match the LUM 〇 energy level of the organic material underneath, so that the illuminating element can have a better luminous efficiency. Therefore, the present invention can provide a top-emitting or double-sided light-emitting organic electro-active element or an organic electroluminescent display having a long life of 7 and a good effect. The above is only the preferred remuneration of the present invention, and all the changes and (4) of the patents made by the present invention are covered by the date of this issue. 1304305 [Simple Description of the Drawings] Fig. 1 is a side cross-sectional view showing a conventional organic electroluminescent device. Figure 2 is a schematic cross-sectional view of a conventional transparent light emitting display. Figure 3 is a top plan view of one embodiment of an electronic device for displaying an image of the present invention. Fig. 4 is a side cross-sectional view showing the organic electroluminescent device shown in Fig. 3. [Main component symbol description] 1 Electronic device 10 Organic electroluminescence display 12 Display area 14 Control circuit 15 Input element 16 Lean line drive is 18 Scan line driver 20 Organic electroluminescent element 22 Data line 24 Scan line 26 Sub-pixel Circuit 27 substrate 28 hole transport layer 29 anode 30 light-emitting layer 31 hole injection layer 32 electron transport layer 34 electron injection layer 36 thin metal layer 38 doped buffer layer 40 transparent electrode 42 transparent cathode 100 organic electroluminescent element 102 Glass substrate 104, 106, 108, 110 film 112 top layer 114, 116 electrode contact end 200 transparent light emitting display 202 cathode 13 1304305 204 electron injection bonding layer 206 electron transport layer 208 hole transport layer 210 anode layer 212 substrate