This application claims the priority benefit of Taiwan application serial no. 101134026, filed on Sep. 17, 2012. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.
1. Field of the Invention
The invention relates to an organic light emitting diode (OLED), more particularly, the invention relates to an OLED with a relatively wide luminescence spectrum.
2. Description of Related Art
At present, flat panel displays, e.g., liquid crystal displays (LCD), organic light emitting diode (OLED) displays, plasma display panels (PDP), and field emission displays (FED) have become indispensible home appliances. The OLED displays are characterized by no viewing angle restriction, low production costs, high response speed (at least 100 times the response speed of the LCD), low power consumption, self-illumination, the direct current driving function applicable to portable devices, wide operating temperature range, lightness, and so on. Hence, the OLED displays are likely to replace the LCD and become the next-generation flat displays.
However, the lights respectively emitted from the OLEDs may have varying luminescence spectra on account of the process of the OLEDs, i.e., the color tone may alter even when each OLED displays the same color. Thereby, the issue of color shift may occur in the OLED display panels, which poses a negative impact on the display performance of the OLED display panels. Accordingly, it is rather important for designers of OLED display panels to reduce the color shift of the lights emitted from the OLEDs.
The invention is directed to an organic light emitting diode (OLED) capable of expanding the width of luminescence spectra of emitted lights, so as to fix color shift on an OLED display panel.
In an embodiment of the invention, an OLED that has a plurality of light emitting regions is provided. The OLED includes an anode layer, a cathode layer, an organic light emitting layer, and a wavelength shift layer. The organic light emitting layer is disposed between the anode layer and the cathode layer and correspondingly provides the light emitting regions with a plurality of emitted lights. Here, the organic light emitting layer has a fixed thickness. The wavelength shift layer is disposed outside the organic light emitting layer, the cathode layer, and the anode layer. A wavelength range at half-peak of the combination of the emitted lights is wider than a wavelength range at half-peak of one of the emitted lights.
In view of the above, the wavelength ranges of the emitted lights corresponding to different light emitting regions are different from one another in the OLED described herein. Hence, a wavelength range at half-peak of the combination of the emitted lights is widened, so as to fix color shift in the OLED display panel.
In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanying figures are described in detail below.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
As indicated in
The organic light emitting layer 130 includes the hole injection layer 131, the hole transport layer 133, the emitting layer 135, the electron transport layer 137, and the electron injection layer 139 that are sequentially arranged from bottom to top. Namely, the emitting layer 135 is disposed between the electron transport layer 137 and the hole transport layer 133. The electron injection layer 139 is disposed between the cathode layer 140 and the electron transport layer 137. The hole injection layer 131 is disposed between the anode layer 120 and the hole transport layer 133.
When the organic light emitting layer 130 is affected by an electric field of the anode layer 120 and the cathode layer 140, the organic light emitting layer 130 correspondingly provides the light emitting regions 100a and 100b with emitted lights, and peak wavelengths of the emitted lights of the organic light emitting layer 130 are shifted by the optical shift portions 150a and 150b, so as to generate emitted lights L11 and L12. Since the thicknesses of the optical shift portions 150a and 150b are different from each other, i.e., the peak wavelengths of the emitted lights are shifted to different extents, the peak wavelengths of the emitted light L11 and the emitted light L12 are different. Thereby, the wavelength range at half-peak of the emitted light L11 is different from the wavelength range at half-peak of the emitted light L12. After the luminescence spectra of the emitted lights L11 and L12 are combined, the wavelength range at half-peak of the emitted light of the OLED 100 is wider than the wavelength range at half-peak of the light L11 or L12. Thereby, color shift (e.g., color shift caused by variations in film thickness during the process and/or viewing angle color shift) in the OLED display panel containing the OLED 100 may be reduced, and the process window of film thickness of the OLED 100 may be relatively increased.
As shown by the luminescence spectra of the emitted lights L11 and L12 in
In
Besides, peak wavelengths of the emitted lights of the organic light emitting layer 130′ corresponding to the light emitting regions 100a and 100b are shifted by the optical shift portions 150a′ and 150b′, so as to generate emitted lights L11′ and L12′. Since the thicknesses of the optical shift portions 150a′ and 150b′ are different from each other, the wavelength ranges at half-peak of the emitted light L11′ and the emitted light L12′ are different. Therefore, if the overall luminescence spectrum of the OLED 100′ is observed, it is found that the wavelength range at half-peak of the emitted light of the OLED 100′ is wider than the wavelength range at half-peak of the light L11′or L12′. Thereby, color shift in the OLED display panel containing the OLED 100′ may be reduced, and the process window of film thickness of the OLED 100′ may be relatively increased.
As indicated in
Besides, peak wavelengths of the emitted lights of the organic light emitting layer 230 corresponding to the light emitting regions 200a and 200b are shifted by the optical shift layers 250a and 250b, so as to generate emitted lights L21 and L22. Since the refractive indices of the optical shift layers 250a and 250b are different from each other, i.e., the peak wavelengths of the emitted lights are shifted to different extents, the wavelength ranges at half-peak of the emitted light L21 and the emitted light L22 are different. Therefore, if the overall luminescence spectrum of the OLED 200 is observed, it is found that the wavelength range at half-peak of the emitted light of the OLED 200 is wider than the wavelength range at half-peak of the light L21 or L22. Thereby, color shift in the OLED display panel containing the OLED 200 may be reduced, and the process window of film thickness of the OLED 200 may be relatively increased.
Besides, peak wavelengths of the emitted lights of the organic light emitting layer 230′ corresponding to the light emitting regions 200a and 200b are shifted by the optical shift layers 250a′ and 250b′, so as to generate emitted lights L21′ and L22′. Since the refractive indices of the optical shift layers 250a′ and 250b′ are different from each other, the wavelength ranges at half-peak of the emitted light L21′ and the emitted light L22′ are different. Therefore, if the overall luminescence spectrum of the OLED 200′ is observed, it is found that the wavelength range at half-peak of the emitted light of the OLED 200′ is wider than the wavelength range at half-peak of the light L21′ or L22′. Thereby, color shift in the OLED display panel containing the OLED 200′ may be reduced, and the process window of film thickness of the OLED 200′ may be relatively increased.
The organic light emitting layer 330 includes a hole injection layer 331, a hole transport layer 333, a plurality of emitting layers (e.g., emitting layers 335a and 335b), an electron transport layer 337, and an electron injection layer 339. The emitting layers (e.g., the emitting layers 335a and 335b) are made of the same material but have different doped concentrations.
As indicated in
The emitting layers 335a and 335b correspondingly provide the light emitting regions 300a and 300b with the emitted lights L31 and L32. Since the doped concentrations of the emitting layers 335a and 335b are different from each other, the peak wavelengths of the emitted light L31 and the emitted light L32 are different. Thereby, the wavelength range at half-peak of the emitted light L31 is different from the wavelength range at half-peak of the emitted light L32. Therefore, if the overall luminescence spectrum of the OLED 300 is observed, it is found that the wavelength range at half-peak of the emitted light of the OLED 300 is wider than the wavelength range at half-peak of the light L31 or L32. Thereby, color shift in the OLED display panel containing the OLED 300 may be reduced, and the process window of film thickness of the OLED 300 may be relatively increased.
In addition, the emitting layers 335a′ and 335b′ correspondingly provide the light emitting regions 300a and 300b with the emitted lights L31′ and L32′. Since the doped concentrations of the emitting layers 335a′ and 335b′ are different from each other, the wavelength ranges at half-peak of the emitted light L31′ and the emitted light L32′ are different. Therefore, if the overall luminescence spectrum of the OLED 300′ is observed, it is found that the wavelength range at half-peak of the emitted light of the OLED 300′ is wider than the wavelength range at half-peak of the light L31′ or L32′. Thereby, color shift in the OLED display panel containing the OLED 300′ may be reduced, and the process window of film thickness of the OLED 300′ may be relatively increased.
In the previous embodiments, the anode layer (e.g., the anode layer 120, 120′, 220, 220′, 320, or 320′), the organic light emitting layer (e.g., the organic light emitting layer 130, 130′, 230, 230′, 330, or 330′), and the cathode layer (e.g., the cathode layer 140, 140′, 240, 240′, 340, or 340′) in the OLED (e.g., the OLED 100, 100′, 200, 200′, 300, or 300′) are sequentially arranged from bottom to top; however, in other embodiments, the anode layer (e.g., the anode layer 120, 120′, 220, 220′, 320, or 320′), the organic light emitting layer (e.g., the organic light emitting layer 130, 130′, 230, 230′, 330, or 330′), and the cathode layer (e.g., the cathode layer 140, 140′, 240, 240′, 340, or 340′) in the OLED (e.g., the OLED 100, 100′, 200, 200′, 300, or 300′) may be sequentially arranged from top to bottom. In this case, the hole injection layer (e.g., the hole injection layer 131, 131′, 231, 231′, 331, or 331′), the hole transport layer (e.g., the hole transport layer 133, 133′, 233, 233′, 333, or 333′), the emitting layer (e.g., the emitting layer 135, 135′, 235, 235′, 335, or 335′), the electron transport layer (e.g., the electron transport layer 137, 137′, 237, 237′, 337, or 337′), and the electron injection layer (e.g., the electron injection layer 139, 139′, 239, 239′, 339, or 339′) in the organic light emitting layer may be correspondingly adjusted to be sequentially arranged from top to bottom.
To sum up, the peak wavelengths of the emitted lights corresponding to different light emitting regions are different from one another in the OLED described herein; that is, the wavelength range at half-peak of one emitted light is different from the wavelength range at half-peak of another emitted light. Hence, if the overall luminescence spectrum of the OLED is observed, it is found that the wavelength range at half-peak of the emitted light of the OLED is wider than the wavelength range at half-peak of one of the lights, so as to fix color shift in the OLED display panel. Moreover, the overcoat layer or the buffer layer may be made of an inorganic dielectric material, such that the cost barrier of manufacturing the OLED may be lowered down.
Although the invention has been described with reference to the above embodiments, it will be apparent to one of the ordinary skill in the art that modifications to the described embodiment may be made without departing from the spirit of the invention. Accordingly, the scope of the invention will be defined by the attached claims not by the above detailed descriptions.
Number | Date | Country | Kind |
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101134026 | Sep 2012 | TW | national |