OPTOELECTRONIC DEVICE AND METHODS OF USE

Abstract

Provided is a device comprising a light-emitting optoelectronic element and a photocurrent-generating optoelectronic element, wherein the device further comprises an opaque element that prevents light emitted by the light-emitting optoelectronic element from reaching the photocurrent-generating optoelectronic element via a pathway within the device.

Claims

1. A device comprising a light-emitting optoelectronic element and a photocurrent-generating optoelectronic element, wherein the device further comprises an opaque element that prevents light emitted by the light-emitting optoelectronic element from reaching the photocurrent-generating optoelectronic element via a pathway within the device.

2. The device of claim 1, wherein the light-emitting optoelectronic element and the photocurrent-generating optoelectronic element have identical composition, wherein the light-emitting optoelectronic element is under an effective forward bias and the photocurrent-generating optoelectronic element is under an effective reverse bias.

3. The device of claim 1, wherein the light-emitting optoelectronic element comprises an emission layer and the photocurrent-generating optoelectronic element comprises an absorption layer.

4. The device of claim 3, wherein the emission layer has a band gap E1, wherein the photocurrent-generating layer has a band gap E2, and wherein E1 is larger than E2.

5. The device of claim 3, wherein the emission layer comprises an organic compound and the absorption layer comprises an organic compound.

6. The device of claim 3, wherein the emission layer comprises material selected from the group consisting of quantum dots and nanorods, and the absorption layer comprises material selected from the group consisting of quantum dots and nanorods.

7. The device of claim 3, wherein the emission layer comprises nanorods, and the absorption layer comprises nanorods.

8. The device of claim 3, wherein the emission layer comprises phosphors and the absorption layer comprises phosphors.

9. The device of claim 1, where the emission layer comprises one or more heterojuntions and the absorption layer comprises one or more heterojunctions

Description

PREPARATIVE EXAMPLE 1

Quantum Dot Synthesis

[0094] The reactions were carried out in a standard Schlenk line under N.sub.2 atmostsphere. Technical grade trioctylphosphine oxide (TOPO) (90%), technical grade trioctylphosphine (TOP) (90%), technical grade octylamine (OA) (90%), technical grade trioctylamine (TOA) (90%), technical grade octadecene (ODE) (90%), CdO (99.5%), Zn acetate (99.99%), S powder (99.998%), and Se powder (99.99%) were obtained from Sigma Aldrich. ACS grade chloroform, and methanol were obtained from Fischer Scientific. All chemicals were used as received.

[0095] The Synthesis of Red Quantum Dots

[0096] Red CdSe/CdS/ZnS were prepared in a manner similar to established methods [Lim, J. et al. Preparation of highly luminescent nanocrystals and their application to light-emitting diodes. Adv. Mater. 19, 1927-1932, 2007]. 1.6 mmol of CdO powder (0.206 g), 6.4 mmol of OA and 40 mL of TOA in a 200 ml three-neck round-bottom flask were degassed at 150 C. for 30 min under vacuum. Then, the solution heated to 300 C. under N.sub.2 atmosphere. At 300 C., 0.4 mL of 1.0 M TOP:Se which was previously prepared in glove box was swiftly injected into the Cd-containing reaction mixture. After 45 sec, 1.2 mmol of n-octanethiol dissolved in 6 ml of TOA was slowly injected at a rate of 1 mL min.sup.1 via a syringe pump. The reaction mixture was then allowed to stir for an additional 30 min at 300 C. Simultaneously, 16 ml of 0.25 M Zn-oleate solution dissolved in TOA was prepared in a separate reaction flask with Zn acetate. the Zn-oleate solution were slowly injected into the CdSe reaction flask, following by injecting 6.4 mmol of n-octanethiol dissolved in 6 ml of TOA at a rate of 1 mL min.sup.1 using a syringe pump.

[0097] The Synthesis of Green Quantum Dots

[0098] Green CdSe/ZnS (gradient composition shell) quantum dots were prepared in a manner with a similar to established methods. [Bae, W. et al Highly Efficient Green-Light-Emitting Diodes Based on CdSe/ZnS Quantum Dots with a Chemical-Composition Gradient, Adv. Mater. 21, 1690-1694, 2009] 0.2 mmol of CdO, 4 mmol of Zn acetate, 4 mmol of OA and 15 ml of ODE were prepared in 100 ml three-neck round-bottom flask, degassed at 120 C. for 30 min under vacuum. The solution heated to 300 C. under N.sub.2 atmosphere. At 300 C., 0.1 mmol of Se and 3.5 mmol of Se dissolved in 2 ml of TOP was swiftly injected into the reaction flask using a syringe. The reaction solution was then allowed to stir for an additional 10 min at 300 C., before being rapidly cooled by an air jet.

PREPARATIVE EXAMPLE 2

Bi-Directional Screen Fabrication

[0099] For the spin-coated QD LED/photodetector (PD), the devices were fabricated on ITO-coated glass substrates (sheet resistance of 1525/). The pre-patterned ITO substrates were cleaned with acetone and isopropanol, consecutively, and then treated with UV-ozone for 15 min. PEDOT:PSS (Clevios P VP AI 4083) was spin-coated onto the ITO at 4000 rpm and baked at 120 C. for 5 min in air and 180 C. for 15 min in a glove box. Then TFB (H.W. Sands Corp.) was spin-coated using m-xylene (5 mg/ml) at 3000 rpm, followed by baking at 180 C. for 30 min in a glove box. After washing twice with chloroform and methanol mixture (1:1 volume ratio), QDs were finally dispersed in chloroform solution (30 mg/ml), and spin-cast on top of the TFB layer at 2000 rpm and then subsequently annealed at 180 C. for 30 min.

[0100] ZnO (30 mg/ml in butanol for ZnO) was spin-coated at 3000 rpm and annealed at 100 C. for 30 min. ZnO nanoparticles were synthesized following the literature [J. Mater. Chem. 18, 1889-1894 (2008)]. In brief, a solution of potassium hydroxide (1.48 g) in methanol (65 ml) was added to zinc acetate dihydrate (2.95 g) in methanol (125 ml) solution and the reaction mixture was stirred at 60 C. for 2 h. The mixture was then cooled to room temperature and the precipitate was washed twice with methanol. After ETL spin-casting, 100 nm thick Al cathode was deposited by an electron-beam evaporator at a rate of 1 /s. The final product of QD LED and QD PD were combined together using a carbon tape (TED Pella, INC) (FIG. 3). Since the carbon tape was placed on the interface of the QD LED and the QD PD, green light could not be transferred from the green QD LED to the red QD PD through the transparent glass substrate.

EXAMPLE 3

Demonstration of Detection of External Object using the Bi-Directional Screen of Example 2

[0101] FIG. 10 shows the experimental results. The graph shows the dark current flow in the red QD PD. In step 1, an effective reverse bias is applied only on the red QD pixel to turn only the red QD PD on. At 2V the red QD PD has a current of about 4 micro ampere. In step 2, an effective forward bias is applied on the green QD pixel to turn the green QD LED on. Since the QD pixels are optically isolated, the red QD PD has a same current of 4 micro ampere as in step 1. In step 3, a 4-inch silicon wafer is placed 5 mm in front of the bi-directional touch screen. At this point, the current in the red PD is 30 micro ampere which is eight times bigger. This is because the green light from the green QD LED reflects from the surface of the silicon wafer and hits the red QD PD, giving it an additional increase in current. In conclusion, bi-directional touch screen was able to detect the silicon wafer located 5 mm in front of it.

[0102] A comparative device was also tested in which no opaque element was present. When the green QD LED was emitting light, the red QD PD was generating photocurrent, even when no external object was present. When an external object was present, the photocurrent from the red QD PD was not significantly larger than the photocurrent in the absence of the external object. It is considered that in the comparative device, a significant amount of light from the green QD LED reached the red QD PD via one or more direct pathway (i.e., a pathway that did not require reflection or scattering from an external object).

[0103] Device measurements were performed in dark to exclude the effect of an external light source.

PREPARATIVE EXAMPLE 4

Synthesis of Nanorods

[0104] Synthesis of CdS nanorod (NR) seeds: First, 2.0 g of trioctylphosphine oxide (TOPO), 0.67 g of octadecylphosphonic acid (ODPA) and 0.128 g of CdO in a 50 mL three-neck round-bottom flask were degassed at 150 C. for 30 min under vacuum and then heated to 370 C. under Ar. After Cd-ODPA complex was formed at 370 C., 16 mg of S dissolved in 1.5 mL of trioctylphosphine (TOP) was swiftly added into the flask with a syringe. Consequently, the reaction mixture was quenched to 330 C. where the CdS growth was carried out. After 15 min, CdS NR growth was terminated by cooling to room temperature. The final solution was dissolved in chloroform and centrifuged at 2000 rpm. The precipitate was re-dissolved in chloroform, and then prepared as a solution for the next step. This solution of CdS NRs had an optical density of 0.1 (for 1 cm optical path length) at the CdS band edge absorption peak when diluted by factor of 100.

[0105] Synthesis of CdS/CdSe nanorod heterostructure (NRH) seeds. Following the formation of CdS NRs and cooling the reaction mixture from 330 C. to 250 C., 20 mg of Se dissolved in 1.0 mL of TOP was slowly added at 250 C. at a rate of 4 ml/h via syringe pump (total injection time 15 min). The reaction mixture was then allowed to stir for an additional 10 min at 250 C. before being rapidly cooled to room temperature. The final solution was dissolved in chloroform, and centrifuged at 2000 rpm. The precipitate was re-dissolved in chloroform, and then prepared as a solution for the next step. This solution of CdS/CdSe NRHs had an optical density of 0.1 (for 1 cm optical path length) at the CdS band edge absorption peak when diluted by factor of 100.

[0106] Synthesis of CdS/CdSe/ZnSe dual heterjunction nanorods (DHNRs). CdS/CdSe/ZnSe DHNRs were synthesized by growing ZnSe onto CdS/CdSe nanorod heterostructures. For Zn precursor, 6 mL of octadecene, 1.13 g (4 mmol) of oleic acid and 0.18 g (1.0 mmol) of Zn acetate were degassed at 150 C. for 30 min. The mixture was heated to 250 C. under N.sub.2 atmosphere, and consequently Zn-oleate was formed after 1 h. Then, 2 mL of previously prepared CdS/CdSe stock solution was injected into Zn-oleate solution after cooling to 50 C. Chloroform was allowed to evaporate for 30 min under vacuum at 70 C. ZnSe growth was initiated by a slow injection of the Se precursor containing 18.5 mg (0.25 mmol) of Se dissolved in 1.0 ml of TOP to the reaction mixture during heating from 180 C. to 300 C. Thickness of ZnSe on CdS/CdSe nanorod heterostructures was controlled by the amount of Se injected. The ZnSe growth was terminated by removing the heating mantle after injecting the desired amount of Se precursor. The resulting nanorods had structure depicted in FIG. 8.

[0107] Individual optoelectronic elements involving nanorods were constructed having the following layers: glass; ITO; PEDOT:PSS mixture; TFB:F.sub.4TCNQ mixture; NR layer; ZnO, Aluminum.

EXAMPLE 5

Characteristics of Optoelectronic Elements

[0108] The characteristics of the individual optoelectronic elements were determined as described above. In the table below, an individual optoelectronic element containing nanorods is referred to as a NR-LED, and an individual optoelectronic element containing quantum dots is referred to as a QD-LED. The NR-LED and QD-LED were compared to various light-emitting diodes (LEDs) in which the absorption/emission material is an organic compound or mixture of organic compounds (organic light-emitting diodes, or OLEDs), according to the results published in the following reference publications: [0109] Ref 1. Organic bifunctional devices with emission and sensing abilities, Japanese Journal of Applied Physics 46, 1328 (2007) [0110] Ref 2. Integrated organic blue led and visible-blind uv photodetector, Journal of Physical Chemistry C 115, 2462 (2011) [0111] Ref 3. High performance organic integrated device with ultraviolet photodetective and electroluminescent properties consisting of a charge-transfer-featured naphthalimide derivative, Applied Physics Letters 105, 063303 (2014) [0112] Ref 4. High performance organic ultraviolet photodetector with efficient electroluminescencerealized by a thermally activated delayed fluorescence emitter, Applied Physics Letters 107, 043303 (2015) [0113] Ref 5. High Efficiency and Optical Anisotropy in Double-Heterojunction Nanorod Light-Emitting Diodes, ACS Nano 9, 878 (2015)

TABLE-US-00001 Responsivity Absorption Emitter Responsivity Measurement Range for Material Results (mA/W) Conditions Photodetection OLED in CuPc/PPR N/A with Xe light N/A Ref. 1 (no power info) OLED in P2NHC 3 (at 2.5 V) with 390 nm 300-420 nm Ref. 2 77 (at 16 V) (no power info) OLED in CzPhONI ~139 (at 3 V) with 350 nm 300-420 nm Ref. 3 (0.6 mW/cm.sup.2) OLED in TCTA 127 (at 2.5 V with 350 nm N/A Ref. 4 (0.2-12.4 mW/cm.sup.2) NR-LED DHNR 108 (at 0 V) with 405 nm laser 300-780 nm 183 (at 2 V) (100 mW/cm.sup.2) QD-LED CdSe/CdS/ZnS 10 (at 0 V) with 405 nm laser 300-780 nm 30 (at 2 V) (100 mW/cm.sup.2) Max Luminous Current/Power Luminance (cd/m.sup.2) Efficiency Comments OLED in 1 at 5 V, Blue N/A Dual functioning Ref. 1 1000 at 10 V 16x16 Passive (Max L: 9720) matrix OLED in 500 at 4 V, Blue 2.2 cd/A No TPD Ref. 2 16000 at 9 V 4.9 lm/W contribution OLED in 50 at 5 V, Blue 0.33 cd/A Broad EL spectrum Ref. 3 1400 at 10 V 200 ms rise time OLED in 100 at 5 V, Blue 8.2 cd/A Broad EL spectrum Ref. 4 10000 at 10 V 4.9 lm/W 200 ms rise time (Max L: 27000 NR-LED 3000 at 3 V, Red 27.5 cd/A LED Efficiencies 30000 at 10 V 36.5 lm/W from Ref 5. (Max L: 76000 ~0.2 ms rise time QD-LED 1500 at 3 V, Red 7.8 cd/A Efficiencies from 10000 at 10 V 8.9 lm/W Ref 5. (Max L: 23000 ~1 ms rise time

[0114] In the table above, it is noted that both QDs and NRs have superior absorption range, luminance, and rise time as compared to the various OLEDs. Further NRs are superior to QDs in responsivity and rise time.

EXAMPLE 6

Response Times of Devices made with Nanorods

[0115] Individual PDs were made using NR as described above. Response times were measured as described above. Results were as follows:

Nanorod PD Response Times

[0116]

TABLE-US-00002 Laser wavelength f3dB response time 730 nm 5500 Hz 0.18 ms 400 nm 10 kHz 0.1 ms

EXAMPLE 7

44 Array of Optoelectronic Elements

[0117] An array of 16 optoelectronic elements in a 44 square array was fabricated as follows. As shown in FIGS. 11A through 11E, the device was fabricated on patterned indium tin oxide (ITO) on glass substrates. PEDOT:PSS (Clevios P VP AI 4083) conductive polymer was coated onto ITO at 4000 rpm and annealed at 120 C in air for 5 minutes. The device were transferred into a glove box and annealed at 180 C for 20 minutes. Then, 7 mg/mL solution of TFB/F4TCNQ mixture dissolved in m-xylene was spin-coated at 3000 rpm and annealed at 180 C for 30 minutes. Nanorods (synthesized as described above) (60 mg/mL) in chloroform after washing twice with 1:1 volume ratio of chloroform and methanol was spin coated at 2000 rpm, then subsequently annealed at 180 C for 30 minutes. 30 mg/mL solution of ZnO in butanol was then spin-coated at 3000 rpm and annealed at 100 C for 30 minutes. A 100 nm thick Al cathode was then deposited by electron-beam evaporation technique. The device was encapsulated with a cover glass using epoxy (NOA 86) in a glovebox.

[0118] The commercially available Arduino Uno and Mega (Arduino company) were used to control the devices for bidirectional display application. In addition to applying effective forward bias to turn on LED devices with the Arduino, it can measure the photocurrent and relay trigger signals from the external light sources. The board can be programmed with the Arduino Integrated Development Environment (IDE) software.

EXAMPLE 8

Demonstration of Detection of Specific Light Source with a 44 Array

[0119] The specific light source was a green laser. Initially, all sixteen optoelectronic elements were put into effective reverse bias. The associated circuitry was arranged so that, when the current detector for a specific optoelectronic element detected current, the bias would flip from effective reverse bias to effective forward bias and remain in effective forward bias for 1 second before flipping back to effective reverse bias. When the laser was turned on and aimed at of one of the optoelectronic elements, that element began to glow with yellow light and remained glowing for 1 second before becoming dark again. As the pen was moved from one optoelectronic element to the next, the optoelectronic element on which the laser's light fell glowed and stayed glowing for one second. The motion of the pen traced out several patterns, for example, a triangle of three of the four optoelectronic elements, and the array of optoelectronic elements emitted light in the same pattern for 1 second before returning to a dark state.