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  • 1.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB.
    Murto, Petri
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB.
    Andersson, Mats R.
    Wang, Ergang
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB.
    On the Design of Host-Guest Light-Emitting Electrochemical Cells: Should the Guest be Physically Blended or Chemically Incorporated into the Host for Efficient Emission?2019In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 7, no 18, article id 1900451Article in journal (Refereed)
    Abstract [en]

    It has recently been demonstrated that light‐emitting electrochemical cells (LECs) can be designed to deliver strong emission with high efficiency when the charge transport is effectuated by a majority host and the emission is executed by a minority guest. A relevant question is then: should the guest be physically blended with or chemically incorporated into the host? A systematic study is presented that establishes that for near‐infrared‐(NIR‐) emitting LECs based on poly(indacenodithieno[3,2‐b]thiophene) (PIDTT) as the host and 4,7‐bis(4,4‐bis(2‐ethylhexyl)‐4H‐silolo[3,2‐b:4,5‐b′]dithiophen‐2‐yl)benzo[c][1,2,5]‐thiadiazole (SBS) as the guest the chemical‐incorporation approach is preferable. The host‐to‐guest energy transfer in LEC devices is highly efficient at a low guest concentration of 0.5%, whereas guest aggregation and ion redistribution during device operation severly inhibits this transfer in the physical‐blend devices. The chemical‐incorporation approach also results in a redshifted emission with a somewhat lowered photoluminescence quantum yield, but the LEC performance is nevertheless very good. Specifically, an NIR‐LEC device comprising a guest‐dilute (0.5 molar%) PIDTT‐SBS copolymer delivers highly stabile operation at a high radiance of 263 µW cm−2 (peak wavelength = 725 nm) and with an external quantum efficiency of 0.214%, which is close to the theoretical limit for this particular emitter and device geometry.

  • 2.
    Tang, Shi
    et al.
    The Organic Photonics and Electronics Group, Umeå University: LunaLEC AB, Umeå University, Umeå, Sweden Umeå, Sweden Umeå, Sweden.
    Murto, Petri
    Wang, Jia
    The Organic Photonics and Electronics Group, Umeå University, Umeå, Sweden.
    Larsen, Christian
    The Organic Photonics and Electronics Group, Umeå University; LunaLEC AB, Umeå University, Umeå, Sweden Umeå, Sweden Umeå, Sweden.
    Andersson, Mats R.
    Wang, Ergang
    Edman, Ludvig
    The Organic Photonics and Electronics Group, Umeå University; LunaLEC AB, Umeå University, Umeå, Sweden Umeå, Sweden.
    On the Design of Host-Guest Light-Emitting Electrochemical Cells: Should the Guest be Physically Blended or Chemically Incorporated into the Host for Efficient Emission?2019In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 7, no 18, article id 1900451Article in journal (Refereed)
    Abstract [en]

    It has recently been demonstrated that light-emitting electrochemical cells (LECs) can be designed to deliver strong emission with high efficiency when the charge transport is effectuated by a majority host and the emission is executed by a minority guest. A relevant question is then: should the guest be physically blended with or chemically incorporated into the host? A systematic study is presented that establishes that for near-infrared-(NIR-) emitting LECs based on poly(indacenodithieno[3,2-b]thiophene) (PIDTT) as the host and 4,7-bis(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b ']dithiophen-2-yl)benzo[c][1,2,5]-thiadiazole (SBS) as the guest the chemical-incorporation approach is preferable. The host-to-guest energy transfer in LEC devices is highly efficient at a low guest concentration of 0.5%, whereas guest aggregation and ion redistribution during device operation severly inhibits this transfer in the physical-blend devices. The chemical-incorporation approach also results in a redshifted emission with a somewhat lowered photoluminescence quantum yield, but the LEC performance is nevertheless very good. Specifically, an NIR-LEC device comprising a guest-dilute (0.5 molar%) PIDTT-SBS copolymer delivers highly stabile operation at a high radiance of 263 mu W cm(-2) (peak wavelength = 725 nm) and with an external quantum efficiency of 0.214%, which is close to the theoretical limit for this particular emitter and device geometry.

  • 3. Xiong, Wenjing
    et al.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Murto, Petri
    Zhu, Weiguo
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Ergang
    Combining Benzotriazole and Benzodithiophene Host Units in Host-Guest Polymers for Efficient and Stable Near-Infrared Emission from Light-Emitting Electrochemical Cells2019In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 7, no 15, article id 1900280Article in journal (Refereed)
    Abstract [en]

    A set of host-guest copolymers with alternating benzodithiophene and benzotriazole (BTz) derivatives as host units and 4,7-bis(5-bromothiophen-2-yl)-benzo[c][1,2,5]thiadiazole as the minority guest are synthesized, characterized, and evaluated for applications. A light-emitting electrochemical cell (LEC) comprising such a host-guest copolymer delivers fast-response near-infrared (NIR) emission peaked at 723 nm with a high radiance of 169 mu W cm(-2) at a low drive voltage of 3.6 V. The NIR-LEC also features good stability, as the peak NIR output only drops by 8% after 350 h of continuous operation. It is, however, found that the LEC performance is highly sensitive to the detailed chemical structure of the host backbone, and that the addition of electron-donating thiophene bridging units onto the BTz unit is highly positive while the inclusion of fluorine atoms results in a drastically lowered performance, presumably because of the emergence of hydrogen bonding within the active material.

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