Table 2 Technology spillovers involved in white LED technology innovations identified in this study

From: Rapid technological progress in white light-emitting diodes and its source in innovation and technology spillovers

Inv.

S/O

Comm.

LED innovation

Spillover

Enablers

Origin

Ref.

Area of improvement

1926

1994

1996

LED phosphors

Use of phosphors for light down conversion in LEDs

Firm experience with phosphors

Materials science (S), cathode ray tubes (T)

35,62,63

Enabled light down conversion in LEDs

1967

1996

1996

YAG:Ce phosphor

Use of YAG:Ce phosphor in a first white LED product

Firm experience with phosphors; firm working in multiple industries

Chemistry (S), materials science (S), fluorescent lighting (T), cathode ray tubes (T)

35,37,64,65,66

Enabled white LED products. ηS, ηC

1967

1996

<2002

YGAG phosphor

Use of YGAG phosphor in first warm white LEDs

Firm experience with phosphors; firm working in multiple industries

Chemistry (S), materials science (S)

37,66,67,68

Enabled warm white LEDs. ηS, ηC

1982

1996

<2007

Patterned sapphire substrate (PSS)

Use of anti-reflective properties of substrate patterns in LEDs

Not identified

Optics and photonics (S), materials science and technology (S,T), nature-inspired material design (T)

69,70,71,72,73

ηLE, ηIQ (depending on chip architecture; Supplementary Note 2)

1971

1999

<2003

Indium tin oxide (ITO) current spreading layer

Use of ITO current spreading layer in white LEDs

Public mission-oriented R&D funding; flexibility of public funding; industry–academia partnership

Optics and photonics (S), materials science and technology (S,T), optoelectronic devices (T)

72,74,75,76

ηVf, ηLE (depending on chip architecture; Supplementary Note 2)

1997

2000 2002

2005

258 phosphor

Use of luminescent ‘258’ nitridosilicate compound as LED phosphor

Flexibility of public funding; freedom of search; international industry–academia partnership

Chemistry (S), materials science (S)

77,78,79,80

ηS, ηC

1984

2003

2009

Quantum dot phosphor

Use of quantum dots for light down conversion in LEDs

Public mission-oriented R&D funding; communication at a conference; commercial success in a different market

Solid-state physics (S), photochemistry (S), nanotechnology (T)

81,82,83,84

ηS, ηC

1972

2005

2015

PFS phosphor

Use of knowledge in luminescent materials and skills in ‘wet’ chemical synthesis to synthesize PFS compound and optimize it as LED phosphor

Public mission-oriented R&D funding; international industry–academia partnership; university alumni networks

Chemistry (S), materials science (S)

85,86,87

ηS, ηC

2008

2013

2015

SLA phosphor

Use of knowledge about existing cuboidal nitride compounds to identify and synthesize structurally similar SLA phosphor

Industry–academia partnership

Structural chemistry (S), materials science (S), solid-state physics (S)

88,89,90,91

ηS, ηC

  1. ‘Inv.’ denotes the the year of initial invention, identified by the earliest literature source describing a specific invention or idea (for example, a particular chemical composition) in a field outside white LED lighting that eventually ‘spilled over’ (that is, got repurposed or applied) to white LED lighting. ‘S/O’ denotes the year of spillover, identified by the earliest reported or patented application of the initial invention or idea in white LED technology. LED innovations in the table are ordered by the S/O year. Note the two S/O years for the 258 phosphor, which represent two independently occurring spillovers that contributed to this innovation. ‘Comm.’ refers to the the year of commercial application, identified as the year of the first recorded application of the initial idea or invention in a commercial LED product. ‘Enablers’ column summarizes our findings on various factors that enabled or supported spillovers described in ‘Spillover’ column. ‘Origin’ column represents knowledge domains in which spillovers initially emerged, where (S) denotes a scientific discipline and (T) is an area of technology. ‘Ref.’ column refers to literature sources for the represented non-LED inventions, spillovers and white LED innovations. ‘Area of improvement’ column summarizes the impact of spillovers on different aspects of white LED technology, for example, improvements in particular sub-efficiencies. Supplementary Note 5 provides a detailed description of the represented phosphor-related innovations and spillovers.
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