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Keywords:

  • BODIPY;
  • fullerenes;
  • photochemistry;
  • photosensitizers;
  • upconversion

Abstract

C60-boron dipyrromethene (BODIPY) dyads (C-1 and C-2) were prepared as heavy-atom-free organic triplet photosensitizers for triplet-triplet annihilation (TTA) based upconversion. BODIPY-C≡C-triphenylamine chromophores were used as the light-harvesting antennas and C60 was used as the singlet energy acceptor and the spin convertor to facilitate the intersystem crossing (ISC) of the dyads from the singlet excited state to the triplet excited state. The C60 dyads strongly absorb visible light (molar extinction coefficients of up to 118800 M−1 cm−1 at 539 nm) and have a long-lived triplet excited state (τT=32.3 μs). The photophysical properties of the C60-dyads were studied with steady-state and time-resolved spectroscopy. Photoexcitation of the dyad with visible light produces firstly the singlet excited state of the antenna, then the singlet excited state of the C60 unit through intramolecular energy transfer. In turn, the triplet excited state of the C60 unit will be populated because of the intrinsic ISC property of C60. As a proof of concept, the dyads were used as heavy-atom-free organic triplet photosensitizers for TTA-based upconversion.