Bare quantum dots superlattice photonic devices

Patent metadata

Field	Value
Publication number	US-9515209-B2
Application number	US-201615068076-A
Country	US
Kind code	B2
Filing date	Mar 11, 2016
Priority date	Nov 14, 2013
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

Manipulation of the passivation ligands of colloidal quantum dots and use in QD electronics. A multi-step electrostatic process is described which creates bare QDs, followed by the formation of QD superlattice via electric and thermal stimulus. Colloidal QDs with original long ligands (i.e. oleic acid) are atomized, and loaded into a special designed tank to be washed, followed by another atomization step before entering the doping station. The final step is the deposition of bare QDs onto substrate and growth of QD superlattice. The method permits the formation of various photonic devices, such as single junction and tandem solar cells based on bare QD superlattice, photodetectors, and LEDs. The devices include a piezoelectric substrate with an electrode, and at least one layer of bare quantum dots comprising group IV-VI elements on the electrode, where the bare quantum dots have been stripped of outer-layer ligands.

First claim

What is claimed is:

1. A method for making a thin film device, comprising the steps:
providing quantum dots comprising group IV-VI elements, wherein the quantum dots contain a ligand;
atomizing the quantum dots;
washing the ligand from the quantum dots, further comprising
placing the quantum dots into a washing apparatus, wherein the washing apparatus comprises:
a cylindrical mixing unit, having a top wall, a bottom wall and tubular side wall;
a quantum dot solution input disposed in the top half of the mixing unit;
an agitator blade disposed on the bottom wall;
a quantum dot solution output disposed in the bottom half of the mixing unit;

adding a wash solution to the washing apparatus;
subjecting the quantum dots to shearing forces formed by the washing apparatus;

atomizing the washed quantum dots;
doping the atomized and washed quantum dots, wherein the doping further comprises:
introducing the atomized and washed quantum dots to an electrolyte solution, a replacement ion, or an electrical charge, wherein:
the electrolyte solution is introduced by placing the quantum dots into an electrolyte introduction apparatus, wherein the electrolyte introduction apparatus further comprises:
a cylindrical mixing unit, having a top wall, a bottom wall and tubular side wall;
a quantum dot solution input disposed in the top half of the mixing unit;
an agitator blade disposed on the bottom wall;
a quantum dot solution output disposed in the bottom half of the mixing unit;
adding an electrolyte solution to the electrolyte introduction apparatus;
subjecting the quantum dots to shearing forces formed by the electrolyte introduction apparatus;

the replacement ion is introduced by placing the quantum dots into an ion exchange apparatus, wherein the ion exchange apparatus further comprises:
a cylindrical mixing unit, having a top wall, a bottom wall and tubular side wall;
a quantum dot solution input disposed in the top half of the mixing unit;
an agitator blade disposed on the bottom wall;
a quantum dot solution output disposed in the bottom half of the mixing unit;
adding an ion exchange solution to the ion exchange apparatus;
subjecting the quantum dots to shearing forces formed by the electrolyte introduction apparatus;

the electrical charge is introduced by subjecting the quantum dots to alternating positive and negative surface charges on the bare quantum dots electrochemically or electrically;

transferring the doped quantum dots to a deposition spray device;
applying the quantum dots to a piezoelectric substrate, wherein the quantum dots are applied by spraying or charged deposition, wherein charged deposition further comprises:
applying a charge to the quantum dots in the atomizer, on the spray head of the atomizer, or a combination thereof;
applying a reverse charge to the piezoelectric substrate;
spraying the charged quantum dots at the piezoelectric substrate, thereby causing the quantum dots to attract to the piezoelectric substrate;

annealing the quantum dots to the piezoelectric substrate to form a bare quantum dot superlattice, wherein the annealing is performed using an alternating electric current, a direct current, thermal modulation, or a combination thereof.

2. The method of claim 1 , wherein the wash solution is methanol.

3. The method of claim 2 , further comprising adding n-butyl alcohol to the quantum dots prior to methanol washing.

4. The method of claim 1 , wherein the atomization is performed with a transducer or ultrasonic vibration device.

5. The method of claim 4 , wherein the atomization is performed in toluene.

6. The method of claim 1 , wherein the electrolyte solution is poly(allylamine hydrochloride), 2-mercaptoethylamine, poly(styrene sulfonate), or thioglycolic acid.

7. The method of claim 6 , wherein the electrolyte solution is washed off in a bath of deionized water.

8. The method of claim 1 , wherein the ion exchange solution is a metal halide in a solution.

9. The method of claim 1 , wherein the surface charge on the bare quantum dots is provided by a charge plate disposed in a quantum dot holding container or atomizer spray head.

10. The method of claim 1 , wherein the bare quantum dots are deposited to form at least one alternating layer of n-type bare quantum dots and p-type bare quantum dots.

Assignees

• Lewis Jason Erik
• Jiang Xiaomei Jane
• Univ South Florida

Inventors

• Lewis Jason Erik
• Jiang Xiaomei Jane

Classifications

• H01L31/035236

  Electricity · mapped topic

• H01L31/18

  Electricity · mapped topic

• H01L31/0324 Primary

  Electricity · mapped topic

• H01L31/035218

  Electricity · mapped topic

• H10F77/146

  Superlattices; Multiple quantum well structures · CPC title