Non-radiatively pumped wavelength converter

• US 8,455,903 B2
• Filed: 04/19/2010
• Issued: 06/04/2013
• Est. Priority Date: 04/20/2009
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Leatherdale, Catherine A., Schardt, Craig R.
• Primary Examiner(s): YUSHIN, NIKOLAY K
• Application Number:
  US13/264,817
• Publication Number:
  US 20120032142A1
• Time in Patent Office: 1,142 Days
• Field of Search: 257/13, 257/98, 257/E33.061, 257/E33.067, 977/932, 977/950, 977/952
• US Class Current: 257/98
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 33/502 Wavelength conversion materials

Abstract

A light source comprises an electroluminescent device that generates pump light and a wavelength converter that includes an absorbing element for absorbing at least some of the pump light. A first layer of light emitting elements is positioned proximate the absorbing element for non-radiative transfer of energy from the absorbing element to the light emitting elements. At least some of the light emitting elements are capable of emitting light having a wavelength longer than the wavelength of the pump light. In some embodiments the electroluminescent device is a light emitting diode (LED) that has a doped semiconductor layer positioned between the LED'"'"'s active layer and the light emitting elements. The first doped semiconductor layer may have a thickness in excess of 20 nm. A second layer of light emitting elements may be positioned for non-radiative energy transfer from the first layer of light emitting elements.

Claims

1. A light source, comprising:

an electroluminescent device capable of generating pump light;

an absorbing element capable of absorbing at least some of the pump light; and

a plurality of light emitting elements positioned proximate the absorbing element for non-radiative transfer of energy from the absorbing element to the light emitting elements, at least some of the light emitting elements being capable of emitting light having a wavelength longer than the wavelength of the pump light,

wherein the absorbing element comprises a absorbing layer that absorbs at least some of the pump light, and wherein the absorbing layer is a semiconductor layer having an energy gap having a first value on a first side closer to the electroluminescent device and a second value on a second side closer to the light emitting elements, the first value being greater than the second value.

2. A light source as recited in claim 1, wherein the absorbing element further comprises a semiconductor quantum well proximate the second side of the absorbing layer.

3. A light emitting diode device, comprising

a light emitting diode (LED) structure comprising an active semiconductor layer disposed between a first doped semiconductor layer and a second doped semiconductor layer, the active semiconductor layer capable of emitting pump light at a first wavelength;

a plurality of light emitting elements arranged above the first doped semiconductor layer, the light emitting elements being capable of emitting light at a second wavelength longer than the first wavelength following non-radiative excitation; and

an absorbing element disposed between the LED structure and the light emitting elements,

wherein the first doped semiconductor layer has a thickness in excess of 20 nm, and wherein the absorbing element comprises an absorbing layer capable of absorbing at least some of the pump light emitted by the active layer, the absorbing layer further comprises a semiconductor quantum well proximate a first side of the absorbing layer, the first side of the absorbing layer facing the plurality of light emitting elements, and wherein the absorbing layer is a semiconductor layer having an energy gap having a first value on a first side closer to the first doped semiconductor layer and a second value on a second side closer to the light emitting elements, the first value being greater than the second value.

4. A light source, comprising:

an electroluminescent device capable of generating pump light at a pump wavelength;

an absorbing element capable of absorbing at least some of the pump light; and

a plurality of first nanoparticles positioned proximate the absorbing element for non-radiative transfer of energy from the absorbing element to the first nanoparticles, and a plurality of second nanoparticles positioned proximate the first nanoparticles for non-radiative transfer of energy from the first nanoparticles to the second nanoparticles, at least some of the first nanoparticles having energy levels corresponding to a first wavelength longer than the pump wavelength and at least some of the second nanoparticles being capable of emitting light at a second wavelength longer than the first light wavelength,

wherein the light emitting elements comprise nano-phosphor structures, and wherein at least some of the nanoparticles capable of emitting light at the second wavelength are arranged to form second wavelength pixels across at least some of the light source and at least some of the second nanoparticles capable of emitting light at the third wavelength are arranged to form third wavelength pixels across at least some of the light source, and wherein the absorbing layer is a semiconductor layer having an energy gap having a first value on a first side closer to the electroluminescent device and a second value on a second side closer to the first nanoparticles, the first value being greater than the second value.