[0019] A method for improving the luminous efficiency of semiconductor-type carbon nanotubes, the method comprising:
[0020] Preparing carbon nanotube bundles containing semiconductor-type carbon nanotubes with different band gaps; the carbon nanotube bundles are all composed of semiconductor-type carbon nanotubes, or contain a small amount of metal-type carbon nanotubes;
[0021] The method for preparing carbon nanotube bundles includes:
[0022] a) Using micromachines to combine different carbon nanotubes into carbon nanotube bundles;
[0023] b) Using physical and chemical methods to directly grow carbon nanotube bundles;
[0024] c) Dissolve carbon nanotubes in chemical reagents, separate and obtain carbon nanotube bundles of different sizes through chemical and physical methods
[0025] The carbon nanotube bundle is prepared as a light-emitting device, and the excitation light with energy close to or equal to the band gap of the wide band gap semiconductor carbon nanotube in the carbon nanotube bundle is selected to excite the carbon nanotube bundle to increase the narrow band gap semiconductor carbon in the carbon nanotube bundle The photoluminescence efficiency of nanotubes; the excitation light includes lasers, light-emitting diodes and broad-spectrum light sources;
[0026] Or prepare the carbon nanotube bundle as a light-emitting device, and apply a bias voltage at both ends of the carbon nanotube bundle to improve the electroluminescence efficiency of the narrow band gap semiconductor carbon nanotubes in the carbon nanotube bundle; where a bias voltage is applied to both ends of the carbon nanotube bundle. At this time, ohmic electrode contacts need to be prepared at both ends of the carbon nanotube bundle.
[0027] There are many methods for preparing nanotube bundles containing semiconductor carbon nanotubes with different band gaps. As an example, we dissolve carbon nanotubes in chemical reagents, and separate and obtain carbon nanotube bundles of different sizes through chemical and physical methods. The specific method is as follows: A certain amount of semiconductor carbon nanotubes contains a large amount of carbon nanotubes. Add to heavy water. The heavy water contains 1-2wt% sodium dodecylbenzene sulfonate. Put it in an ultrasonic system for several hours to disperse the carbon nanotubes into the heavy water; then immediately filter with 0.7 micron fiber glass filter paper The nanotube solution after sonication was immediately centrifuged for several hours in a centrifuge, and the upper half of the clear nanotube solution was taken out. By adjusting the experimental conditions, the last part of the clear nanotube solution basically only contains the carbon nanotube bundles wrapped by the surfactant.
[0028] Generally, the solution containing a single carbon nanotube is a colorless and transparent solution. However, the color of the carbon nanotube bundle solution we prepared was gray, indicating that the solution contained a large amount of carbon nanotube bundles.
[0029] In order to study the luminous efficiency of carbon nanotube bundles, we used different excitation lights to excite the carbon nanotube bundle solution to obtain the photoluminescence (PL) spectrum and the photoluminescence excitation (PLE) spectrum of the carbon nanotube bundle solution. Spectra such as figure 1 Shown.
[0030] From figure 1 It can be seen from the PL spectrum in the that when the wavelength is 568 nanometers (its energy is exactly equal to the exciton state energy corresponding to the second electron energy band of (6,5) semiconducting carbon nanotubes), when the carbon nanotubes are excited, (6 5) The luminous intensity of the band edge (at 982 nm) of the semiconductor carbon nanotube is basically close to the corresponding intensity obtained when the excitation wavelength is 831 nm. Since the 831-nanometer excitation light is non-resonant excitation for (6,5) semiconductor carbon nanotubes, the number of excitons excited is much less than the number of excitons excited by the 568-nanometer excitation light. However, their similar fluorescence intensity indicates that (6,5) semiconductor carbon nanotubes have higher luminous efficiency under 831 nm excitation light. Since the energy corresponding to the 831 nm excitation light is exactly equal to the band gap of the (5, 4) semiconducting carbon nanotubes, the selected energy is the same as the wide band gap semiconducting carbon nanotubes in the carbon nanotube bundle (such as (5, 4) carbon nanotubes). Excitation light with a band gap close to or equal to) excites the carbon nanotube bundle to improve the photoluminescence efficiency of the narrow band gap semiconductor carbon nanotubes (such as (6, 5) carbon nanotubes) in the carbon nanotube bundle.
[0031] figure 1 PLE in gives the luminous intensity of (9,5) carbon nanotubes with a band edge located at 1246 nm under different excitation light energy. It can be seen that when the excitation light energy is equal to the band edge of the wide band gap (6, 5) carbon nanotubes, the narrow band gap (9, 5) carbon nanotubes have the highest luminous intensity. This further shows that the excitation of wide band gap carbon nanotubes can improve the luminous efficiency of narrow band gap carbon nanotubes.
[0032] For carbon nanotube electroluminescent devices, since excitons generated in wide band gap carbon nanotubes can be quickly transferred to narrow band gap carbon nanotubes, the luminous efficiency of narrow band gap carbon nanotubes can also be improved.
[0033] The above examples illustrate that by preparing nanotube bundles containing semiconductor carbon nanotubes with different band gaps and preparing the nanotube bundles into light-emitting devices, the excitons generated in the wide band gap carbon nanotubes can be quickly transferred to the narrow band gap carbon nanotubes. Recombination at the band edge of the narrow band gap carbon nanotubes can improve the luminous efficiency of the narrow band gap carbon nanotubes.
