Patent Publication Number: US-2020295239-A1

Title: Light conversion devices incorporating quantum dots

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefits of U.S. Patent Application No. 62/816,595, filed Mar. 11, 2019, and U.S. Patent Application No. 62/964,101, filed Jan. 21, 2020, each of which is incorporated herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The implementations of the disclosure relate generally to semiconductor devices and, more specifically, to light conversion devices incorporating quantum dots (QDs) and methods of fabricating the same. 
     BACKGROUND 
     Quantum dots (QDs) are semiconductor particles in nanoscale sizes. When a QD is illuminated by light, an electron in the QD may be excited to a state of higher energy. The QD may thus emit light of a certain wavelength. QDs of various shapes, sizes, compositions, etc. may emit light with various wavelengths. For example, a relatively larger QD may emit light with a relatively longer wavelength, while a relatively smaller QD may emit light with a relatively shorter wavelength. 
     SUMMARY 
     The following is a simplified summary of the disclosure in order to provide a basic understanding of some aspects of the disclosure. This summary is not an extensive overview of the disclosure. It is intended to neither identify key or critical elements of the disclosure, nor delineate any scope of the particular implementations of the disclosure or any scope of the claims. Its sole purpose is to present some concepts of the disclosure in a simplified form as a prelude to the more detailed description that is presented later. 
     In accordance with one or more aspects of the present disclosure, a light conversion device is provided. The light conversion device may include a porous structure that may include one or more nanoporous materials. In some embodiments, the one or more nanoporous materials may include a plurality of pores. The light conversion device may also include a plurality of quantum dots placed in the porous structure. In some embodiments, the plurality of quantum dots may include a first plurality of quantum dots configured to convert light of a first color into light of a second color, and a second plurality of quantum dots configured to convert the light of the first color into light of a third color. 
     In some embodiments, each of the plurality of pores has a nanoscale size. 
     In some embodiments, the one or more nonporous materials may further include a matrix that may include at least one of a semiconductor material, glass, plastic, metal, or polymer. In some embodiments, the semiconductor material may include at least one of Si, AlN, InGaN, or AlGaN. 
     In some embodiments, the light-conversion device may further include a light source configured to produce the light of the first color. 
     In some embodiments, the light of the first color may include violet light. 
     In some embodiments, the second color may include a green color and the third color may include a red color. 
     In some embodiments, the plurality of quantum dots may further include a third plurality of quantum dots configured to convert the light of the first color to light of a fourth color. The fourth color may include a blue color. 
     In some embodiments, the first plurality of quantum dots, the second plurality of quantum dots, and the third plurality of quantum dots may be placed in a first portion of the porous structure, a second portion of the porous structure, and a third portion of the porous structure, respectively. 
     In accordance with one or more aspects of the present disclosure, a method for fabricating a light conversion device is provided. The method may include providing a porous structure that may include one or more nanoporous materials. The one or more nanoporous materials may include a plurality of pores. The method may also include placing a plurality of quantum dots in the porous structure. The plurality of quantum dots may include a first plurality of quantum dots configured to convert light of a first color into light of a second color, and a second plurality of quantum dots configured to convert the light of the first color into light of a third color. 
     In some embodiments, providing the porous structure may include forming the one or more nanoporous materials using a solid material. The solid material may include at least one of a semiconductor material, glass, plastic, metal, or polymer in some embodiments. The semiconductor material may include at least one of Si, AlN, InGaN, or AlGaN in some embodiments. 
     In some embodiments, forming the one or more nanoporous materials using the solid material may include etching the solid material to form the plurality of pores. In some embodiments, placing the plurality of quantum dots in the porous structure may include placing the first plurality of quantum dots in a first portion of the porous structure, placing the second plurality of quantum dots in a second portion of the porous structure, and placing the third plurality of quantum dots in a third portion of the porous structure 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the disclosure. The drawings, however, should not be taken to limit the disclosure to the specific embodiments, but are for explanation and understanding only. 
         FIGS. 1A, 1B, and 1C  are block diagrams illustrating structures associated with an example process for fabricating a light conversion device in accordance with some embodiments of the present disclosure. 
         FIG. 2A  is a cross-sectional Scanning Electron microscopy (SEM) image of an example light conversion device in accordance with one or more aspects of the present disclosure. 
         FIG. 2B  depicts a photoluminescence (PL) spectrum of an example light conversion device in accordance with one or more aspects of the present disclosure. 
         FIG. 3  is a flowchart illustrating an example of a process for fabricating a light conversion device in accordance with one or more aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the disclosure provide for light conversion devices incorporating quantum dots (QDs) and methods of fabricating the same. In accordance with one or more aspects of the present disclosure, a light conversion device may include a nanoporous structure comprising one or more nanoporous materials. The nanoporous materials may include pores (e.g., voids) of nanoscale sizes (e.g., a size of the order of 1 nm to 1000 nm or larger). The light conversion device may further include quantum dots placed in the nanoporous structure (e.g., the pores in the nanoporous structure). The quantum dots may convert input light into light of various colors. For example, the quantum dots in the light conversion device may include one or more first quantum dots for converting the input light into green light, one or more second quantum dots for converting the input light into red light, one or more third quantum dots for converting the input light into blue light, etc. 
     In accordance with one or more aspects of the present disclosure, methods for fabricating the light conversion device are provided. The methods may include fabricating the nanoporous structure using a solid material. For example, the nanoporous materials may be formed by etching the solid material. Examples of the solid materials may include semiconductor materials (Si, GaN, AlN, InGaN, AlGaN, etc.), glass, plastic, metal, polymer, etc. The methods may further include placing the quantum dots in the nanoporous structure. For example, the quantum dots may be loaded into one or more of the pores in the nanoporous structure. 
     The nanoporous structure described herein may work as a great natural receptacle for quantum dot loading and may thus enable easy manufacturing of the light-conversion device. For example, the light-conversion device may be fabricated using a photolithography method, an inkjet printing method, etc. The porous structure may also increase internal scattering and effective pathways of light traveling in the light-conversion device. The porous structure may thus improve the light conversion efficiency of the loaded QDs. 
     Examples of embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. It should be understood that the following embodiments are given by way of illustration only to provide thorough understanding of the disclosure to those skilled in the art. Therefore, the present disclosure is not limited to the following embodiments and may be embodied in different ways. Further, it should be noted that the drawings are not to precise scale and some of the dimensions, such as width, length, thickness, and the like, can be exaggerated for clarity of description in the drawings. Like components are denoted by like reference numerals throughout the specification. 
     Referring to  FIGS. 1A, 1B, and 1C , structures related to an example process for fabricating a light conversion device in accordance with some embodiments of the present disclosure are illustrated. As shown in  FIG. 1A , a solid material  110  may be obtained for fabricating a light conversion device in accordance with the present disclosure. The solid material  110  may be fabricated into a porous structure comprising nanoporous materials (also referred to herein as the “nanoporous structure”). 
     For example, as illustrated in  FIG. 1B , the solid material  110  may be fabricated into a porous structure  120 . In some embodiments, the porous structure  120  may be fabricated by etching the solid material  110  using chemical etching and/or any other suitable etching technique. The porous structure  120  may include nanoporous materials comprising pores. As shown in  FIG. 1B , the porous structure  120  may include a matrix structure  121  comprising the solid material and pores  123 . Each of the pores  123  may have a nanoscale size (e.g., a size of the order of 1 nm to 1000 nm or larger). The porosity of the porous structure  120  and/or the nanomaterials (e.g., a fraction of the volume of the pores  123  over a total volume of the porous structure  120 ) can be in a range of 10% to 90%. In some embodiments, a diameter of a pore  123  may be equal to or greater than 10 nm. The pores  123  may be dispersed in a three-dimensional space. 
     As illustrated in  FIG. 1C , one or more quantum dots (QDs) may be placed into the porous structure  120  to fabricate a light conversion device  130 . For example, the QDs may be loaded into the porous structure  120  by infiltrating a liquid (such as toluene, polydimethylsiloxane (PDMS), etc.) containing QDs into the porous structure  120  and/or the nanoporous materials. As the pores  123  are dispersed in a three-dimensional space, the QDs may be loaded into the three-dimensional space occupied by the pores  123 . 
     The QDs may be and/or include semiconductor particles in nanoscale sizes (also referred to as “nanoparticles”). Each of the QDs may include any suitable semiconductor material that may be used to produce a QD for implementing light conversion devices in accordance with the present disclosure, such as one or more of ZnS, ZnSe, CdSe, InP, CdS, PbS, InP, InAs, GaAs, GaP, etc. Multiple QDs placed in the porous structure  120  may or may not include the same semiconductor material. 
     Each of the QDs may have a suitable core-shell structure that may include a core and/or one or more shells. The core and the shells may or may not include the same semiconductor material. As an example, one or more of the QDs may have a core comprising a suitable semiconductor material. As another example, one or more of the QDs may have a core comprising a first semiconductor material (e.g., CdS) and a shell comprising a second semiconductor material (e.g., ZnS). As a further example, one or more of the QDs may have a core (e.g., a CdSe core) and multiple shells (e.g., a first shell comprising ZnSe, a second shell comprising ZnS). Multiple QDs placed in the porous structure may or may not have the same core-shell structures. 
     When excited by electricity or light, a QD may emit light of a certain wavelength and/or a range of wavelengths (also referred to as the “emission wavelength” of the QD). More particularly, for example, the QD may absorb one or more photons with a wavelength shorter than the emission wavelength of the QD. Different QDs (e.g., QDs of various shapes, sizes, and/or materials) may emit light with various wavelengths. For example, a relatively larger QD may emit light with a relatively longer wavelength, while a relatively smaller QD may emit light with a relatively shorter wavelength. 
     In some embodiments, QDs of various emission wavelengths may be placed in the porous structure and/or nanoporous materials to achieve a mixed color emission. For example, as shown in  FIG. 1C , the QDs placed in the porous structure  120  may include one or more QDs  131  with a first emission wavelength (also referred to as the “first QDs”), one or more QDs  133  with a second emission wavelength (also referred to as the “second QDs”), one or more QDs  135  with a third emission wavelength (also referred to as the “third QDs”), etc. QDs  131 ,  133 , and/or  135  may have different sizes, shapes, compositions, etc. to achieve different emission wavelengths. QDs  131 ,  133 , and/or  135  may or may not contain different materials. In one implementation, QDs  131 ,  133 , and/or  135  contain different semiconductor materials. 
     When excited by light  141 , the first QDs may convert light  141  to light  143  with the first emission wavelength. The second QDs may convert the light  141  to light  145  with the second emission wavelength. The third QDs may convert the light  141  to light  147  with the third emission wavelength. The light  141  may be produced by any light source that is capable of producing light. Examples of the light source may include one or more light-emitting diodes, laser diodes, etc. In some embodiments, light  141  may have a wavelength that is not longer than the first emission wavelength, the second emission wavelength, and/or the third emission wavelength. Light  143 ,  145 , and  147  may be of different colors (e.g., red light, green light, blue light). 
     As shown in  FIG. 1C , the first QDs, the second QDs, and the third QDs may be placed in various portions of the porous structure  120  (e.g., a first portion, a second portion, and a third portion of the porous structure  120 , respectively). Each of the portions of the porous structure may include multiple layers of QDs loaded in a three-dimensional space that was formed by one or more portions of the pores  123 . 
     In accordance with one or more aspects of the present disclosure, a light conversion device is provided. The light conversion device may include a porous structure and a plurality of QDs placed in the porous structure. The porous structure may include one or more nanoporous materials. The nanoporous materials and/or the porous structure may include a matrix structure comprising one or more semiconductor materials (Si, GaN, AlN, etc.), glass, plastic, metal, polymer, etc. The nanoporous materials and/or the porous structure may further include one or more pores and/or voids. 
     The plurality of QDs may include QDs of various emission wavelengths, such as one or more first QDs with a first emission wavelength (also referred to herein as the “first plurality of QDs”), one or more second QDs with a second emission wavelength (also referred to herein as the “second plurality of QDs”), one or more third QDs with a third emission wavelength (also referred to herein as the “third plurality of QDs”), etc. The first QDs, the second QDs, and the third QDs may or may not have the same size, shape, and/or material. In some embodiments, one or more of the first QDs may have a first size and/or a first shape. One or more of the second QDs may have a second size and/or a second shape. One or more of the third QDs may have a third size and/or a third shape. In one implementation, the first size may be different from the second size and/or the third size. In one implementation, the first shape may be different from the second shape and/or the third shape. In one implementation, one or more of the first QDs, the second QDs, and/or the third QDs may include different materials. 
     The light conversion device may convert light of a certain wavelength into light of one or more desired wavelengths (e.g., may convert light of a shorter wavelength to light of longer wavelength(s)). In some embodiments, the light conversion device may convert light of a first color into one or more of light of a second color, light of a third color, light of a fourth color, etc. The first color, the second color, the third color, the fourth color may correspond to a first wavelength, a second wavelength, a third wavelength, and a fourth wavelength, respectively. In some embodiments, the first color is different from the second color, the third color, and/or the fourth color. In some embodiments, the second color, the third color, and the fourth color may correspond to a red color, a green color, and a blue color, respectively. In some embodiments, the light of the first color comprises violet light. 
       FIG. 2A  is a cross-sectional SEM image of an example light conversion device in accordance with one or more aspects of the present disclosure. The light conversion device may comprise a porous structure comprising GaN (nanoporous GaN) and QDs placed in the porous structure and/or the nanoporous GaN. As illustrated, when excited by input light having a wavelength of about 420 nm, the light conversion device may convert the input light into red light. 
       FIG. 2B  depicts a PL spectrum of an example light conversion device in accordance with one or more aspects of the present disclosure. As shown, the light conversion device can convert input light having a wavelength of about 420 nm into green light (e.g., light with an emission wavelength of 650 nm). 
     Referring to  FIG. 3 , a flowchart an example 300 of a process for fabricating a light conversion device in accordance with some embodiments of the present disclosure is shown. 
     As illustrated, the method  300  may start at block  310  where a porous structure comprising one or more nanoporous materials is provided. The one or more nanoporous materials may include a matrix structure and a plurality of pores. Each of the pores may have a nanoscale size. 
     In some embodiments, providing the porous structure may include fabricating the porous structure. For example, one or more operations as described in connection with  FIGS. 1A-1B  above may be performed. In some embodiments, fabricating the porous structure may include forming the one or more nanoporous material using a solid material, such as a semiconductor material, glass, plastic, metal, polymer, etc. For example, the solid material may be etched to form pores of nanoscale sizes in the solid material. 
     At block  320 , a plurality of quantum dots may be placed in the porous structure. The quantum dots may have various emission wavelengths and may convert input light into light of a mixed color emission. For example, the quantum dots may convert light of a first color into light of a second color and light of a third color. As another example, the quantum dots may also convert the light of the first color into light of a fourth color. In some embodiments, the second color, the third color, and the fourth color may include a green color, a red color, and a blue color, respectively. In some embodiments, the input light may include violet light. 
     In some embodiments, placing the quantum dots in the porous structure may include performing one or more operations depicted in blocks  321 ,  323 , and/or  325 . At block  321 , a first plurality of quantum dots may be placed into a first portion of the porous structure (e.g., a first plurality of pores in the nanoporous materials). The first plurality of quantum dots may have a first emission wavelength and may convert input light of a first color into light of a second color. The light of the second color may have a wavelength corresponding to the first emission wavelength. 
     At block  323 , a second plurality of quantum dots may be placed into a second portion of the porous structure (e.g., a second plurality of pores in the nanoporous materials). The second plurality of quantum dots may have a second emission wavelength and may convert the input light into light of a third color. The light of the third color may have a wavelength corresponding to the second emission wavelength. 
     At block  325 , a third plurality of quantum dots may be placed into a third portion of the porous structure (e.g., a third plurality of pores in the nanoporous materials). The third plurality of quantum dots may have a third emission wavelength and may convert the input light into light of a fourth color. The light of the fourth color may have a wavelength corresponding to the third emission wavelength. 
     In accordance with one or more aspects of the present disclosure, a display for presenting media content is provided. Examples of media content may include text, audio content, video content, images, graphics, etc. The display may comprise a light conversion device as described herein. The display may be of any suitable size. The display may be incorporated into any suitable computing device, such as mobile phones, laptops, desktops, tablet computer devices, wearable computing devices (e.g., watches, eyeglasses, head-mounted displays, virtual reality headsets, activity trackers, clothing, etc.), televisions, etc. The display may be and/or include a liquid-crystal display (LCD), an organic light-emitting diode (OLED) display, an LED display, a micro-LED display, etc. In some embodiments, the display may be and/or include a flexible display and/or a foldable display. 
     In accordance with one or more aspects of the present disclosure, a light-emitting device is provided. The light-emitting device may comprise a light conversion device as described herein. The light-emitting device may further comprise one or more light-emitting diodes, laser diodes, and/or any other suitable device that is capable of producing light. 
     For simplicity of explanation, the methods of this disclosure are depicted and described as a series of acts. However, acts in accordance with this disclosure can occur in various orders and/or concurrently, and with other acts not presented and described herein. Furthermore, not all illustrated acts may be required to implement the methods in accordance with the disclosed subject matter. In addition, those skilled in the art will understand and appreciate that the methods could alternatively be represented as a series of interrelated states via a state diagram or events. Additionally, it should be appreciated that the methods disclosed in this specification are capable of being stored on an article of manufacture to facilitate transporting and transferring such methods to computing devices. The term “article of manufacture,” as used herein, is intended to encompass a computer program accessible from any computer-readable device or memory page media. 
     The terms “approximately,” “about,” and “substantially” may be used to mean within ±20% of a target dimension in some embodiments, within ±10% of a target dimension in some embodiments, within ±5% of a target dimension in some embodiments, and yet within ±2% in some embodiments. The terms “approximately” and “about” may include the target dimension. 
     In the foregoing description, numerous details are set forth. It will be apparent, however, that the disclosure may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the disclosure. 
     The terms “first,” “second,” “third,” “fourth,” etc. as used herein are meant as labels to distinguish among different elements and may not necessarily have an ordinal meaning according to their numerical designation. 
     The words “example” or “exemplary” are used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. Rather, use of the words “example” or “exemplary” is intended to present concepts in a concrete fashion. As used in this application, the term “or” is intended to mean an inclusive “or” rather than an exclusive “or”. That is, unless specified otherwise, or clear from context, “X includes A or B” is intended to mean any of the natural inclusive permutations. That is, if X includes A; X includes B; or X includes both A and B, then “X includes A or B” is satisfied under any of the foregoing instances. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from context to be directed to a singular form. Reference throughout this specification to “an implementation” or “one implementation” means that a particular feature, structure, or characteristic described in connection with the implementation is included in at least one implementation. Thus, the appearances of the phrase “an implementation” or “one implementation” in various places throughout this specification are not necessarily all referring to the same implementation. 
     As used herein, when an element or layer is referred to as being “on” another element or layer, the element or layer may be directly on the other element or layer, or intervening elements or layers may be present. In contrast, when an element or layer is referred to as being “directly on” another element or layer, there are no intervening elements or layers present. 
     Whereas many alterations and modifications of the disclosure will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that any particular embodiment shown and described by way of illustration is in no way intended to be considered limiting. Therefore, references to details of various embodiments are not intended to limit the scope of the claims, which in themselves recite only those features regarded as the disclosure.