Polymer-Based White-Light-Emitting Electrochemical Cells with Very High Color-Rendering Index Based on Blue-Green Fluorescent Polyfluorenes and Red-Phosphorescent Iridium Complexes

Yoshinori Nishikitani, Tetsuyuki Cho, Soichi Uchida, Suzushi Nishimura, Kenichi Oyaizu, Hiroyuki Nishide

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Application of the concept of three-color (red (R), green (G), and blue (B)) light-mixing to obtain white light is the most suitable way to realize white-light-emitting devices with very high color-rendering indices (CRI). White-light-emitting devices based on the three-color-mixing method could be used to create lighting and display technologies. Here, white-light-emitting electrochemical cells (LECs) with very high CRIs are reported, which were fabricated by using blend films composed of a fluorescent π-conjugated polymer (FCP), poly(9,9-dioctylfluorene-co-benzothiadiazole) (PFBT), and a phosphorescent iridium complex, [Ir(ppy)2(biq)]+(PF6) (where (ppy)=2-phenylpyridinate and biq=2,2′-biquinoline). The LECs fabricated with PFBT, the benzothiadiazole content of which is 0.01 mol %, showed blue electroluminescence (EL) emission originating from the fluorene segments and green EL emission from the benzothiadiazole units simultaneously. White LECs were then realized by adding red-emitting Ir complexes as guest molecules to the blue-green-emitting PFBT. By optimizing the proportions of the PFBT and Ir complexes in the active layers (PFBT/[Ir(ppy)2(biq)]+(PF6)=1:0.2 (mass ratio)), white-light emission with Commission Internationale de l′Eclairage (CIE) coordinates of (0.29, 0.34) and a very high CRI value of 91.5 was achieved through RGB color-mixing. It was noted that the emission mechanism was based on Förster resonance energy transfer and Dexter energy transfer from excited PFBT to [Ir(ppy)2(biq)]+(PF6). The utilization of LECs based on blue-green FCPs and red Ir complexes looks very promising for the prospect of realizing white-light-emitting devices with very high CRIs.

Original languageEnglish
Pages (from-to)463-469
Number of pages7
JournalChemPlusChem
Volume83
Issue number5
DOIs
Publication statusPublished - 2018 May 1

Fingerprint

Iridium
Electrochemical cells
Polymers
Color
Electroluminescence
Energy transfer
Conjugated polymers
Light emission
poly((9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-(2,1',3)-thiadiazole))
Lighting
Display devices
Molecules

Keywords

  • conjugated polymers
  • electrochemical cells
  • FRET
  • phosphorescent triplet emitters
  • white light emission

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

@article{99e4ba68cea5429a8c87e9509bb573a1,
title = "Polymer-Based White-Light-Emitting Electrochemical Cells with Very High Color-Rendering Index Based on Blue-Green Fluorescent Polyfluorenes and Red-Phosphorescent Iridium Complexes",
abstract = "Application of the concept of three-color (red (R), green (G), and blue (B)) light-mixing to obtain white light is the most suitable way to realize white-light-emitting devices with very high color-rendering indices (CRI). White-light-emitting devices based on the three-color-mixing method could be used to create lighting and display technologies. Here, white-light-emitting electrochemical cells (LECs) with very high CRIs are reported, which were fabricated by using blend films composed of a fluorescent π-conjugated polymer (FCP), poly(9,9-dioctylfluorene-co-benzothiadiazole) (PFBT), and a phosphorescent iridium complex, [Ir(ppy)2(biq)]+(PF6)− (where (ppy)−=2-phenylpyridinate and biq=2,2′-biquinoline). The LECs fabricated with PFBT, the benzothiadiazole content of which is 0.01 mol {\%}, showed blue electroluminescence (EL) emission originating from the fluorene segments and green EL emission from the benzothiadiazole units simultaneously. White LECs were then realized by adding red-emitting Ir complexes as guest molecules to the blue-green-emitting PFBT. By optimizing the proportions of the PFBT and Ir complexes in the active layers (PFBT/[Ir(ppy)2(biq)]+(PF6)−=1:0.2 (mass ratio)), white-light emission with Commission Internationale de l′Eclairage (CIE) coordinates of (0.29, 0.34) and a very high CRI value of 91.5 was achieved through RGB color-mixing. It was noted that the emission mechanism was based on F{\"o}rster resonance energy transfer and Dexter energy transfer from excited PFBT to [Ir(ppy)2(biq)]+(PF6)−. The utilization of LECs based on blue-green FCPs and red Ir complexes looks very promising for the prospect of realizing white-light-emitting devices with very high CRIs.",
keywords = "conjugated polymers, electrochemical cells, FRET, phosphorescent triplet emitters, white light emission",
author = "Yoshinori Nishikitani and Tetsuyuki Cho and Soichi Uchida and Suzushi Nishimura and Kenichi Oyaizu and Hiroyuki Nishide",
year = "2018",
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T1 - Polymer-Based White-Light-Emitting Electrochemical Cells with Very High Color-Rendering Index Based on Blue-Green Fluorescent Polyfluorenes and Red-Phosphorescent Iridium Complexes

AU - Nishikitani, Yoshinori

AU - Cho, Tetsuyuki

AU - Uchida, Soichi

AU - Nishimura, Suzushi

AU - Oyaizu, Kenichi

AU - Nishide, Hiroyuki

PY - 2018/5/1

Y1 - 2018/5/1

N2 - Application of the concept of three-color (red (R), green (G), and blue (B)) light-mixing to obtain white light is the most suitable way to realize white-light-emitting devices with very high color-rendering indices (CRI). White-light-emitting devices based on the three-color-mixing method could be used to create lighting and display technologies. Here, white-light-emitting electrochemical cells (LECs) with very high CRIs are reported, which were fabricated by using blend films composed of a fluorescent π-conjugated polymer (FCP), poly(9,9-dioctylfluorene-co-benzothiadiazole) (PFBT), and a phosphorescent iridium complex, [Ir(ppy)2(biq)]+(PF6)− (where (ppy)−=2-phenylpyridinate and biq=2,2′-biquinoline). The LECs fabricated with PFBT, the benzothiadiazole content of which is 0.01 mol %, showed blue electroluminescence (EL) emission originating from the fluorene segments and green EL emission from the benzothiadiazole units simultaneously. White LECs were then realized by adding red-emitting Ir complexes as guest molecules to the blue-green-emitting PFBT. By optimizing the proportions of the PFBT and Ir complexes in the active layers (PFBT/[Ir(ppy)2(biq)]+(PF6)−=1:0.2 (mass ratio)), white-light emission with Commission Internationale de l′Eclairage (CIE) coordinates of (0.29, 0.34) and a very high CRI value of 91.5 was achieved through RGB color-mixing. It was noted that the emission mechanism was based on Förster resonance energy transfer and Dexter energy transfer from excited PFBT to [Ir(ppy)2(biq)]+(PF6)−. The utilization of LECs based on blue-green FCPs and red Ir complexes looks very promising for the prospect of realizing white-light-emitting devices with very high CRIs.

AB - Application of the concept of three-color (red (R), green (G), and blue (B)) light-mixing to obtain white light is the most suitable way to realize white-light-emitting devices with very high color-rendering indices (CRI). White-light-emitting devices based on the three-color-mixing method could be used to create lighting and display technologies. Here, white-light-emitting electrochemical cells (LECs) with very high CRIs are reported, which were fabricated by using blend films composed of a fluorescent π-conjugated polymer (FCP), poly(9,9-dioctylfluorene-co-benzothiadiazole) (PFBT), and a phosphorescent iridium complex, [Ir(ppy)2(biq)]+(PF6)− (where (ppy)−=2-phenylpyridinate and biq=2,2′-biquinoline). The LECs fabricated with PFBT, the benzothiadiazole content of which is 0.01 mol %, showed blue electroluminescence (EL) emission originating from the fluorene segments and green EL emission from the benzothiadiazole units simultaneously. White LECs were then realized by adding red-emitting Ir complexes as guest molecules to the blue-green-emitting PFBT. By optimizing the proportions of the PFBT and Ir complexes in the active layers (PFBT/[Ir(ppy)2(biq)]+(PF6)−=1:0.2 (mass ratio)), white-light emission with Commission Internationale de l′Eclairage (CIE) coordinates of (0.29, 0.34) and a very high CRI value of 91.5 was achieved through RGB color-mixing. It was noted that the emission mechanism was based on Förster resonance energy transfer and Dexter energy transfer from excited PFBT to [Ir(ppy)2(biq)]+(PF6)−. The utilization of LECs based on blue-green FCPs and red Ir complexes looks very promising for the prospect of realizing white-light-emitting devices with very high CRIs.

KW - conjugated polymers

KW - electrochemical cells

KW - FRET

KW - phosphorescent triplet emitters

KW - white light emission

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