Abstract:
A method for manufacturing a quantum-dot element utilizes a reaction chamber for evaporating or sputtering at least one electrode layer or at least one buffer layer on a substrate. A substrate-supporting base is located inside the reaction chamber for fixing the substrate. An atomizer has a gas inlet and a sample inlet. More specifically, the gas inlet and the sample inlet feed the atomizer respectively with a gas and a precursor solution having a plurality of functionalized quantum dots, and thereby form a quantum-dot layer on the substrate. The method for manufacturing a quantum-dot element forms a quantum dot layer with uniformly distributed quantum dots and integrates the processes for forming the quantum-dot layer, the buffer layer, and the electrode layer together in the same chamber.

Description:
This application is a continuation of and claims the benefit of the earlier filing date of co-pending U.S. application Ser. No. 11/187,828, filed Jul. 25, 2005 (of which the entire disclosure of the pending, prior application is hereby incorporated by reference). 
    
    
     BACKGROUND OF INVENTION 
     1. Field of Invention 
     The present invention relates to an apparatus for manufacturing a quantum-dot element and, more particularly, to an apparatus for manufacturing a photoelectric element with colloidal quantum dots. 
     2. Description of Related Art 
     Recently, the hybrid of organic or inorganic materials has become the emphasis of the development in photoelectric materials. On the other hand, the nano-particulate obtained by liquid or gaseous synthesis is also the focus of the development in material technology. Although the nano-particulate as well as the composite of the nano-particulate and the organic molecule inherently have good material property, they become deteriorated when being applied to the photoelectric devices. The main problem lies in that the manufacturing process of the nano-particulate is not compatible with the vacuum process for manufacturing the photoelectric element and, therefore, the manufacturing of the photoelectric element with the nano-particulates can not be carried out in a continuous process. 
     Generally, the quantum dot of the quantum-dot element is formed by either a vacuum process or chemical synthesis. The vacuum process further includes the Molecular Beam Epitaxy (MBE) method, the Chemical Vapor Deposition (CVD) method, and the Ultrahigh Vacuum Physical Vapor Deposition (UHVPVD) method. However, the quantum dots formed by these vacuum processes usually have too large particle sizes (usually larger than 10 nm) and too low densities. Also, the particle sizes are not uniform enough. Therefore, the quantum dots formed by the vacuum process are unsuitable for manufacturing device with large superficial content As for the chemical synthesis, it can produce quantum dots with well-distributed size, which generally ranges from 1 nm to 10 nm. In addition, the quantum dots formed by the chemical synthesis have a higher density, so they can be used to manufacture devices with large superficial content. The quantum-dot layer formed by the conventional chemical synthesis is shown as  FIGS. 1   a  to  1   c . First, the particles  10  and the organic molecules  20  are mixed in an atmosphere of inert gas, which prevents the particles  10  from oxidizing. Namely, the quantum dots are dispersed in the organic solvent, as shown in  FIG. 1   a . Afterwards, the quantum dots in the organic solvent are deposited onto the substrate  30  by spin coating in the grove box, as shown in  FIG. 1   b . Subsequently, the substrate  30  is put into the vacuum evaporation chamber or the sputtering chamber for depositing a carrier transport film or an electrode  40 , as shown in  FIG. 1   c . However, the quantum dots may easily aggregate in the aforesaid process, as shown in  FIG. 2   c . Besides, the product is easily contaminated during the mixing or the spin coating step, and consequently suffers from quality deterioration. Moreover, the product might be damaged when it is transported between different manufacturing apparatuses. In addition to the above-mentioned method, the quantum dots may also be adsorbed onto the substrate by dipping. However, although a uniform layer of quantum dots can be formed, the solvent might easily contaminate other parts of the quantum-dot element such as the carrier transport layer or the electrode. 
     In order to overcome the imperfection of such a non-continuous process, the apparatus for manufacturing a quantum-dot element of the present invention combines the conventional aerosol spraying process with the vacuum process. In particular, the aerosol spraying process is used for introducing the solid powders. Therefore, the organic-inorganic composite element can be manufactured in a single chamber, and the bottleneck of deterioration in material quality can be substantially improved. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide an apparatus for manufacturing a quantum-dot element so that the electrode layer, the emitting material layer, and the carrier transport layer of the quantum-dot element can all be formed in the same apparatus, and thus the quality loss due to transferring between different apparatuses can be substantially avoided. Furthermore, the quantum dots can be distributed uniformly, the sizes of quantum dots can lie in the nano-order, and the performance of the quantum-dot element in light, electricity, and magnetism can be improved. 
     In order to achieve the above object, the apparatus for manufacturing a quantum-dot element having a quantum-dot layer formed on a substrate, comprises a reaction chamber, a substrate-supporting base, and an atomizer. The reaction chamber provides a reaction condition for evaporating or sputtering at least one electrode layer or at least one buffer layer on the substrate. The substrate-supporting base is located inside the reaction chamber for fixing the substrate. The atomizer has a gas inlet and a sample inlet. Moreover, the sample inlet feeds the atomizer with a precursor solution having a plurality of functionalized quantum dots, and thereby forms a quantum-dot layer on the substrate. 
     The apparatus for manufacturing a quantum-dot element of the present invention can produce devices having the functionalized quantum dots, for example, a light-emitting diode, a laser diode, a detective device such as a light sensor or chemical sensor, photonic crystals, light modulators, magnetic thin film, or a battery using solar energy. 
     Generally, the quantum-dot element is constructed of a bottom electrode layer, a buffer layer, a quantum-dot layer, another buffer layer, and a top electrode layer formed on a substrate. The buffer layer is usually composed of at least one carrier injection/exportation layer pair, and can also be omitted optionally. Furthermore, the substrate can be selected according to the function of the resultant element, and can be an ITO glass substrate, a silicon substrate, an Al 2 O 3  substrate, or a GaAs substrate. 
     When the apparatus of the present invention is used, the substrate with or without the bottom electrode layer is fixed on the substrate-supporting base in the deposition chamber first. Subsequently, the buffer layer or the electrode layer is formed by a vacuum deposition process, for example, a Chemical Vapor Deposition (CVD) process, or a Physical Vapor Deposition (PVD) process such as evaporation or sputtering. Therefore, the deposition chamber could be a CVD chamber, an evaporation chamber, or a sputtering chamber. Afterwards, a precursor solution is prepared by considering the size of the droplet sprayed out from the atomizer, the property of the solvent, and the volume of the functionalized quantum dot. Owing to the functionalized group, the quantum dots can be dispersed in the solvent uniformly. Thereafter, the precursor solution is sprayed onto the surface of the substrate by the atomizer to form a quantum-dot layer. Moreover, the quantum dot can be a metal quantum dot, a semiconductor quantum dot, a magnetic quantum dot, an organic molecule quantum dot, or a polymer quantum dot. In addition, the diameter of the quantum dot formed by the present invention is less than 100 nm, and preferably ranges from several nano-meters to tens of nano-meters. The dispersion medium of the quantum dots, i.e. the solvent, can be water, an aqueous solution containing a surfactant, a polar organic solvent such as methanol, a non-polar organic solvent such as toluene, or a polymer solvent such as a diluted solution of a conjugate polymer, an epoxy resin, polymethylmethacrylate, polycarbonate, or a cyclic olefin co-polymer. The type of the atomizer is not restricted, and can be the conventional atomizer that sprays droplets by mixing and pressurizing the gas with the solution, or the supersonic atomizer that produces droplets by using the vibration energy of the piezoelectric ceramics. Besides, the substrate-supporting base is preferably a rotary plate that can drive the substrate to rotate and heat the substrate. More preferably, the substrate support base can adjust the rotation speed and the temperature of the substrate. Preferably, one shutter is mounted between the substrate supporting base and the atomizer, and the other shutter is mounted between the substrate supporting base and the evaporation or sputtering source for preventing the unstable evaporation or sputtering source from depositing on the substrate at the beginning of the heating of the evaporation or sputtering source. Similarly, at the initial stage of the spraying of the precursor solution, the droplets are not uniform enough. Therefore, the shutter is also used for blocking the non-uniform droplets from arriving at the substrate. 
     The preparation of precursor solution is quite important in the present invention. In addition to the functionalization that facilitates the uniform dispersion of the quantum dots, the concentration of the precursor solution should also be calculated precisely. More specifically, the concentration of the precursor solution is calculated first in order to produce droplets containing a predetermined number of quantum dots. Afterwards, a proper amount of quantum-dot powder is dispersed in the solvent to prepare the precursor solution with a predetermined concentration. 
     For example, the average diameter of the functionalized quantum-dot powder is 20 nm, and the average diameter of the droplet sprayed from the atomizer is 100 nm. If each droplet is predetermined to contain only one quantum-dot powder, then the volume concentration of the precursor solution can be calculated as the following equation (1):
 
(20 nm) 3 /{(100 nm) 3 +(20 nm) 3 }=4.63×10 −3 =0.463 V %  (1)
 
     If each droplet is predetermined to contain fifteen quantum-dot powders, then the volume concentration of the precursor solution can be calculated as the following equation (2):
 
[15×(20 nm) 3 ]/[(100 nm) 3 +15×(20 nm) 3 ]=0.1071=10.71 V %  (2)
 
     If for a pair of droplets, only one contains a quantum-dot particle and the other does not, then the volume concentration of the precursor solution will be half the concentration of equation (1). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1   a ˜ 1   c  are schematic views showing the formation of the quantum-dot layer by the chemical synthesis of prior art; 
         FIG. 2   a  is an SEM picture showing the distribution of quantum dots in the quantum-dot layer of prior art; 
         FIG. 2   b  is an SEM picture showing the distribution of quantum dots in the quantum-dot layer formed by the present invention; 
         FIG. 3  is a schematic view showing the structure of the light-emitting element having a ZnSe quantum-dot layer formed by the present invention; 
         FIG. 4  is a schematic view showing the first preferred embodiment of the apparatus for manufacturing the quantum-dot element of the present invention; 
         FIG. 5  is a schematic view showing the second preferred embodiment of the apparatus for manufacturing the quantum-dot element of the present invention; 
         FIG. 6  is a schematic view showing the third preferred embodiment of the apparatus for manufacturing the quantum-dot element of the present invention; 
         FIG. 7  is a schematic view showing the fourth preferred embodiment of the apparatus for manufacturing the quantum-dot element of the present invention; 
         FIG. 8  is a schematic view showing the fifth preferred embodiment of the apparatus for manufacturing the quantum-dot element of the present invention; 
         FIG. 9   a  is a figure showing the relationship between the brightness and the voltage of the light-emitting element manufactured by the present invention; and 
         FIG. 9   b  is a figure showing the relationship between the brightness and the voltage of the light-emitting element manufactured by the prior art. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment 1 
     Preparation of the Precursor Solution Containing CdSe/ZnS Quantum Dot with a Diameter of 3 nm 
     A piezoelectric atomizer that forms toluene droplets with an average diameter of 1000 nm introduces the precursor solution. If the influence to the diameter of the droplet caused by the CdSe/ZnS quantum dot is neglected and if each droplet is predetermined to have one quantum-dot particle, then the volume concentration of the precursor solution can be calculated as the following equation (3):
 
(3 nm) 3 /{(1000 nm) 3 +(3 nm) 3 }=2.70×10 −8   (3)
 
     If each droplet is predetermined to have three quantum-dot particles, then the desired concentration will be three times the concentration obtained from equation (3). Similarly, if each pair of droplets has only one quantum-dot particle, then the desired concentration will be half the concentration obtained from equation (3). 
     Embodiment 2 
     Preparation of the Precursor Solution Containing ZnO Particle with a Diameter of 1 μm 
     The precursor solution is introduced by a conventional atomizer to form water droplets with an average diameter of 15 μm. If the influence to the diameter of the droplet caused by the ZnO particle is neglected and if each droplet is predetermined to have one particle, then the volume concentration of the precursor solution can be calculated as the following equation (4):
 
(1 μm) 3 /{(15 μm) 3 +(1 μm) 3 }=2.96×10 −4   (4)
 
     The volume concentration calculated from equation (4) equals to a weight concentration of 1.62×10 −3 . 
     If each droplet is predetermined to have five particles, then the desired concentration will be five times the concentration obtained from equation (4). Similarly, if each pair of droplets contains only one particle, then the desired concentration will be half the concentration obtained from equation (4). 
     Embodiment 3 
     Preparation of the Precursor Solution Containing Silica Nano-particle with a Diameter of 20 nm 
     The precursor solution is introduced by a piezoelectric atomizer to form water droplets with an average diameter of 100 nm. If the influence to the diameter of the droplet caused by the silica particle is neglected and if each droplet is predetermined to have one particle, then the volume concentration of the precursor solution can be calculated as the following equation (5):
 
(20 nm) 3 /{(100 nm) 3 +(20 nm) 3 }=4.63×10 −3 =0.463 V %  (5)
 
     If each droplet is predetermined to have fifteen particles, then the desired concentration will be fifteen times the concentration obtained from equation (5). Similarly, if each pair of droplets contains only one particle, then the desired concentration will be half the concentration obtained from equation (5). 
     Embodiment 4 
     Manufacturing of the Light-emitting Element having ZnSe Quantum Dots 
     With reference to  FIG. 3 , there is shown a schematic view of the light-emitting element having ZnSe quantum dots according to the present invention. The light-emitting element includes a glass substrate  110 , on which an anode layer  120  made of the conductive glass, a hole transport layer (HTL)  130 , an emitting material layer (EML)  140  composed of CdSe quantum dots, an electron transport layer (ETL)  150 , and a cathode layer  170  made of aluminum are formed sequentially. Moreover, there is usually a LiF layer  160  formed between the cathode layer  170  and the electron transport layer  150 . 
     In the present embodiment, the EML, the HTL, and the ETL can be made of any conventional materials, which are listed in the following table: 
     
       
         
               
               
               
               
               
               
               
             
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
             
           
               
                   
               
               
                   
                 Light- 
                   
                   
                   
                   
                   
               
               
                 Material 
                 Emitting 
                 Green 
                 Red 
                 Yellow 
                 Blue 
                 White 
               
               
                   
               
             
             
               
                 Small 
                 EML 
                 Alq ′ DPT ′ 
                 DCM-2 ′ 
                 Rubrene 
                 TPAN ′ DPAN ′ 
                 TTBND/ 
               
               
                 molecule 
                   
                 Alq 3  ′ Bebq 2  ′ 
                 TMS-SiPc ′ 
                   
                 DPAP ′ 
                 BTX-1 
               
               
                 material 
                   
                 DMQA ′ 
                 DCJTB ′ 
                   
                 Perylene(C 20 H 12 ) ′ 
                   
               
               
                   
                   
                 Coumarin6 ′ 
                 ABTX 
                   
                 DPVBi ′ PPD ′ 
                   
               
               
                   
                   
                 Q ′ NMQ ′ 
                   
                   
                 a-NPD 2  ′ 
                   
               
               
                   
                   
                 Quinacrine 
                   
                   
                 b-NPD ′ 
                   
               
               
                   
                   
                   
                   
                   
                 TTBND ′ 
                   
               
               
                   
                   
                   
                   
                   
                 DCTA ′ TDAPTz 
                   
               
             
          
           
               
                   
                 HTL 
                 TPAC ′ TPD ′ a-NPD ′ 2Me-TPD ′ FTPD ′ Spiro-TPD(TAD) ′ 
               
               
                   
                   
                 t-TNATA ′ OTPAC ′ CuPc ′ TPTE ′ m-MTDATA 
               
               
                   
                 ETL 
                 Alq 3  ′ Bebq 2  ′ BND ′ OXD ′ ZnPBT ′ PBD ′ TAZ 
               
             
          
           
               
                 Polymer 
                 EML 
                 PPV ′ PF ′ MEH-PPV 
                   
                   
                   
                   
               
             
          
           
               
                 material 
                 HTL 
                 PEDOT ′ PAni ′ PVK ′ PTPDES 
               
               
                   
               
             
          
         
       
     
     Wherein the above abbreviations are defined as follows: 
     NPB: 
     N,N′-di(naphthalen-1-yl)-N,N′-di(phenyl)benzidin, 
     α-NPB: 
     N,N′-Bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine,
     DMFL-NPB:   

     N,N′-di(naphthalen-1-yl)-N,N′-di(phenyl)-9,9-dimethyl-fluorene,
     TPD:   

     N,N′-Bis-(3-methylphenyl)-N,N′-bis-(phenyl)-benzidine,
     Spiro-TPD:   

     N,N′-bis-(3-methylphenyl)-N,N′-bis-(phenyl)-spiro,
     DMFL-TPD:   

     N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)-9,9-diphenyl-fluorene,
     Spiro-NPB:   

     N,N′-di(naphthalen-1-yl)-N,N′-diphenyl-spiro),
     TCP:   

     1,3,5-tris(carbazol-9-yl)-benzene,
     TNB:   

     N,N,N′,N′-tetrakis(naphth-1-yl)-benzidine,
     MCP:   

     1,3-bis(carbazol-9-yl)-benzene,
     PVK:   

     poly (N-vinyl carbazole),
     PEDOT:   

     poly (ethylenedioxythiophene,
     PSS:   

     poly (styrene sulfonic acid),
     MEH-PPV:   

     Poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene),
     MEH-BP-PPV:   

     Poly[2-Methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene -co-4,4′-bisphenylenevinylene],
     PF-BV-MEH:   

     Poly[(9,9-dioctylfluoren-2,7-diyl)-co-(1,4-diphenylene-vinylene-2-methoxy-5-{2-ethylhexyloxy }benzene)],
     PF-DMOP:   

     Poly[(9,9-dioctylfluoren-2,7-diyl)-co-(2,5-dimethoxybenzen-1,4-diyl)],
     PFH:   

     Poly[(9,9-dihexylfluoren-2,7-diyl)-alt-co-(benzen-1,4-diyl)],
     PFH-EC:   

     Poly[(9,9-dihexylfluoren-2,7-diyl)-co-(9-ethylcarbazol-2,7-diyl)],
     PFH-MEH:   

     Poly[(9,9-dihexylfluoren-2,7-diyl)-alt-co-(2-methoxy-5-{2-ethylhexyloxy}phenylen-1,4-diyl)],
     PFO:   

     Poly[(9,9-dioctylfluoren-2,7-diyl),
     PF-PPV:   

     Poly[(9,9-di-n-octylfluoren-2,7-diyl)-co-(1,4-vinylenephenylene)],
     PF-PH:   

     Poly[(9,9-dihexylfluoren-2,7-diyl)-alt-co-(benzen-1,4-diyl)],
     PF-SP:   

     Poly[(9,9-dihexylfluoren-2,7-diyl)-alt-co-(9,9′-spirobifluoren-2,7-diyl)],
     Poly-TPD:   

     Poly(N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine,
     Poly-TPD-POSS:   

     Poly(N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine,
     TAB-PFH:   

     Poly[(9,9-dihexylfluoren-2,7-diyl)-co-(N,N′-di(4-butylphenyl)-N,N′-diphenyl-4,4′-diyl-1,4-diaminobenzene)],
     PPB:   

     N,N′-Bis(phenanthren-9-yl)-N,N′-diphenylbenzidine,
     Alq 3 :   

     Tris-(8-hydroxyquinoline)aluminum,
     BAlq 3 :   

     (Bis-(2-methyl-8-quinolinolate)-4-(phenylphenolato)-alumium),
     BCP:   

     2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline,
     CBP:   

     4,4′-Bis(carbazol-9-yl)biphenyl,
     TAZ:   

     3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole 
     In the present embodiment, the apparatus for manufacturing the quantum-dot element is shown in  FIG. 4 . An evaporation chamber  200  having a plurality of evaporation sources  210  is used to deposit the hole transport layer, the quantum-dot emitting layer, and the electron transport layer successively on the substrate  110 . A substrate-supporting base  220  is located in the evaporation chamber  200  for fixing the substrate  110 . In addition, an atomizer  230  is used to pressurize the mixture of a gas and a solution More specifically, nitrogen and a toluene solution containing functionalized CdSe quantum dots are sprayed into the evaporation chamber  200  for generating droplets containing quantum dots. The nitrogen and the toluene solution are fed respectively through a gas inlet  231  and a sample inlet  232 , both of which are connected with the atomizer  230 . Furthermore, several shutters  240  are mounted between the substrate-supporting base and the atomizer  230 , as well as between the substrate supporting base and the evaporation sources  210 . Owing to the shutters  240 , the atomizer  230  and the evaporation sources  210  can be switched and prevented from contaminating with each other. Preferably, a sieve  250  is mounted between the atomizer  230  and the shutter  240  for controlling the size of droplets that deposit on the substrate  110 . Besides, the atomizer  230  is disposed at the bottom of the chamber  200 , and the substrate-supporting base  220  is located at the top of the chamber  200 . Hence, the droplets transported upwardly can deposit uniformly on the substrate and form a quantum-dot layer with uniform distribution of quantum dots. 
     The substrate-supporting base  220  is a rotary plate that drives the substrate to rotate. Also, the substrate-supporting base  220  can heat the substrate so as to increase the uniformity of the hole transport layer and electron transport layer formed by evaporation, as well as the quantum-dot emitting layer formed by atomization. In addition, the solvent on the substrate can be driven out accordingly. The evaporated material includes an organic molecule, an organic metal, an organic semiconductor, a metal, a semiconductor, a hole or electron transport material, and a super conductive material. In particular, the organic molecule contains the small organic molecule that has a molecular weight less than 100,000, and an organic polymer. The organic metal is a molecule having metal and an organic group such as C—R, O—R, N—R, or S—R group, wherein R represents an organic molecule. The organic semiconductor contains an organic compound that has an electrically conductive property and a light-emitting property, such as a conjugate polymer. The metal includes groups 1A, 2A, 3A, 4A, 5A, 6A, 7A, 8A, 1B, and 2B metals in the periodic table. The semiconductor contains the semiconductors of groups 4B and the compound semiconductors of groups 1B, 2B, 3B, 4B, 5B, 6B, and 7B. The hole or electron transport material includes the hole or electron transport materials used for the PLED and OLED. As for the super conductive material, it includes the compounds that have at least two of Y, Ba, Cu, and O elements and other superconductors. 
     When the quantum-dot element is manufactured, the substrate  110  having the anode layer  120  made of the conductive glass is transferred into the evaporation chamber  200  and fixed on the substrate-supporting base  220  first. Simultaneously, the evaporation source  210  is turned on under vacuum condition to form a hole transport layer  130  on the substrate  110 . Afterwards, a high-pressure gas is used to spray out the droplets containing functionalized quantum dots through the atomizer  230 . Subsequently, the evaporation source  210  of the electron transport layer  150  is turned on to form the electron transport layer  150  on the glass substrate  110 . Finally, the glass substrate  110  is transferred out of the chamber, and then sent to other apparatus for depositing the cathode layer  170 . At this point, the manufacture of the light-emitting element is finished. The distribution of quantum dots in the quantum-dot emitting layer  140  can be as shown as  FIG. 2   b.    
     The atomizer  230 , the gas inlet  231 , and the sample inlet  232  are mounted inside the chamber  200  in the present embodiment. Also, those parts can be mounted outside of the chamber  200  except the spray head of the atomizer  230 , as shown in  FIG. 5 . In this preferred embodiment, the crucible is used to serve as the evaporation source, which is melted by the thermal resistance materials such as a tungsten line or a tantalum line. However, the deposition chamber  300  can also use an electron-beam gun  310  to melt the evaporation source, and an externally connected removable atomizer  330  to deposit a thin film on the substrate  320 , as shown in  FIG. 6 . Alternatively, with reference to  FIG. 7 , the laser  410  can be used to gasify the target  420  in the chamber  400 , and the gas  430  can transfer the gasified target material to form the electrode layer or the buffer layer on the substrate  450 . Also, a removable atomizer  440  is externally connected to form the quantum-dot layer on the substrate  450 . Furthermore, in the quartz tube  530  of the chamber  500 , a film is formed on the substrate  520  by the Chemical Vapor Deposition process, as shown in  FIG. 8 . More particularly, the feed inlet  510  is located at one end of the quartz tube  530 , and at the other end of the quartz tube  530 , there is an outlet  540  connecting with a pump. The outlet  540  can generate a pressure difference in the quartz tube  530 . Thus, the pressure difference drives the gas to flow and form a film on the substrate  520 . Similarly, the atomizer  550  serves to form the quantum dots in the film. 
     In the present invention, the carrier transport layer can be deposited optionally before or after the quantum-dot layer is formed. Alternatively, the carrier transport layer and the quantum-dot layer can be formed by turns. Finally, the electrode can also be deposited in the same chamber. As the above-mentioned steps are all carried out in the vacuum chamber, they can be accomplished in a continuous process. Consequently, the manufacturing time and cost are reduced. Besides, the product is effectively prevented from being contaminated, Moreover, the quantum dots can be distributed uniformly on the substrate due to the spraying of the atomizer, The size of the quantum dots can be reduced to nano-meter level successfully. 
     The relationship between the brightness and the exerted voltage of the emitting element having ZnSe quantum dots formed by the present invention is compared with that of the conventional emitting element, of which the quantum-dot layer is formed by coating. As shown in  FIG. 9   a , the brightness of the emitting element manufactured by the present invention reaches 10,000 lumens as the voltage is 9V. However, the brightness of the conventional emitting element is less than 1,000 lumens as the voltage is 9V, as shown in  FIG. 9   b . Therefore, the emitting element manufactured by the apparatus of the present invention exhibits a substantially improved light-emitting efficiency. 
     The above detailed descriptions are given by way of example and not intended to limit the invention solely to the embodiments described herein.