Spin-dependent exciton formation in π-conjugated compounds

被引:427
作者
Wilson, JS
Dhoot, AS
Seeley, AJAB
Khan, MS
Köhler, A
Friend, RH
机构
[1] Univ Cambridge, Cavendish Lab, Cambridge CB3 0HE, England
[2] Sultan Qaboos Univ, Dept Chem, Al Khoud 123, Oman
关键词
D O I
10.1038/35101565
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
The efficiency of light-emitting diodes (LEDs) made from organic semiconductors is determined by the fraction of injected electrons and holes that recombine to form emissive spin-singlet states rather than non-emissive spin-triplet states. If the process by which these states form is spin-independent, the maximum efficiency of organic LEDs will be limited to 25 per cent(1). But recent reports have indicated fractions of emissive singlet states ranging from 22 to 63 per cent(2-5), and the reason for this variation remains unclear. Here we determine the absolute fraction of singlet states generated in a platinum-containing conjugated polymer and its corresponding monomer. The spin-orbit coupling introduced by the platinum atom allows triplet-state emission, so optically and electrically generated luminescence from both singlet and triplet states can be compared directly. We rnd an average singlet generation fraction of 22 +/- 1 per cent for the monomer, but 57 +/- 4 per cent for the polymer. This suggests that recombination is spin-independent for the monomer, but that a spin-dependent process, favouring singlet formation, is effective in the polymer. We suggest that this process is a consequence of the exchange interaction, which will operate on overlapping electron and hole wavefunctions on the same polymer chain at their capture radius.
引用
收藏
页码:828 / 831
页数:4
相关论文
共 24 条
  • [1] Excitonic singlet-triplet ratio in a semiconducting organic thin film
    Baldo, MA
    O'Brien, DF
    Thompson, ME
    Forrest, SR
    [J]. PHYSICAL REVIEW B, 1999, 60 (20): : 14422 - 14428
  • [2] Effect of metal films on the photoluminescence and electroluminescence of conjugated polymers
    Becker, H
    Burns, SE
    Friend, RH
    [J]. PHYSICAL REVIEW B, 1997, 56 (04) : 1893 - 1905
  • [3] THEORETICAL INVESTIGATION OF THE LOWEST SINGLET AND TRIPLET-STATES IN POLY(PARA-PHENYLENE VINYLENE)OLIGOMERS
    BELJONNE, D
    SHUAI, Z
    FRIEND, RH
    BREDAS, JL
    [J]. JOURNAL OF CHEMICAL PHYSICS, 1995, 102 (05) : 2042 - 2049
  • [4] Spatial extent of the singlet and triplet excitons in transition metal-containing poly-ynes
    Beljonne, D
    Wittmann, HF
    Kohler, A
    Graham, S
    Younus, M
    Lewis, J
    Raithby, PR
    Khan, MS
    Friend, RH
    Bredas, JL
    [J]. JOURNAL OF CHEMICAL PHYSICS, 1996, 105 (09) : 3868 - 3877
  • [5] Temperature dependent electron-hole recombination in polymer light-emitting diodes
    Blom, PWM
    deJong, MJM
    Breedijk, S
    [J]. APPLIED PHYSICS LETTERS, 1997, 71 (07) : 930 - 932
  • [6] Spin effects on the luminescence yield of organic light emitting diodes
    Burin, AL
    Ratner, MA
    [J]. JOURNAL OF CHEMICAL PHYSICS, 1998, 109 (14) : 6092 - 6102
  • [7] Improved quantum efficiency for electroluminescence in semiconducting polymers
    Cao, Y
    Parker, ID
    Yu, G
    Zhang, C
    Heeger, AJ
    [J]. NATURE, 1999, 397 (6718) : 414 - 417
  • [8] Synthesis and electronic structure of platinum-containing poly-ynes with aromatic and heteroaromatic rings
    Chawdhury, N
    Kohler, A
    Friend, RH
    Younus, M
    Long, NJ
    Raithby, PR
    Lewis, J
    [J]. MACROMOLECULES, 1998, 31 (03) : 722 - 727
  • [9] Evolution of lowest singlet and triplet excited states with number of thienyl rings in platinum poly-ynes
    Chawdhury, N
    Köhler, A
    Friend, RH
    Wong, WY
    Lewis, J
    Younus, M
    Raithby, PR
    Corcoran, TC
    Al-Mandhary, MRA
    Khan, MS
    [J]. JOURNAL OF CHEMICAL PHYSICS, 1999, 110 (10) : 4963 - 4970
  • [10] Electroluminescence in conjugated polymers
    Friend, RH
    Gymer, RW
    Holmes, AB
    Burroughes, JH
    Marks, RN
    Taliani, C
    Bradley, DDC
    Dos Santos, DA
    Brédas, JL
    Lögdlund, M
    Salaneck, WR
    [J]. NATURE, 1999, 397 (6715) : 121 - 128