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Trap‐Assisted Triplet Emission in Ladder‐Polymer‐Based Light‐Emitting Diodes
Author(s) -
Khodabakhshi Elham,
Ramanan Charusheela,
Michels Jasper J.,
Bonus Sven,
Hertel Dirk,
Meerholz Klaus,
Forster Michael,
Scherf Ulrich,
Blom Paul W. M.
Publication year - 2020
Publication title -
advanced electronic materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.25
H-Index - 56
ISSN - 2199-160X
DOI - 10.1002/aelm.202000082
Subject(s) - electroluminescence , materials science , optoelectronics , diode , light emitting diode , trapping , oled , singlet state , polymer , photochemistry , atomic physics , chemistry , nanotechnology , physics , excited state , ecology , layer (electronics) , composite material , biology
The charge transport and recombination in light‐emitting diodes (LEDs) based on a methyl‐substituted poly( p ‐phenylene) ladder polymer (Me‐LPPP) are investigated. The transport is characterized by a high room‐temperature hole mobility of 2 × 10 −8 m 2 V −1 s −1 combined with anomalously strong electron trapping. Their electroluminescence (EL) spectrum is characterized by a blue singlet emission, a broad green featureless peak, and a yellow‐orange triplet emission. The voltage dependence of the EL spectrum and negative contribution to the capacitance indicate that the triplet‐emission is of trap‐assisted nature, consistent with the strong electron trapping. Consequently, the color purity of the blue emissive Me‐LPPP polymer LEDs can be strongly improved using trap dilution.