Upconversion with ultrabroad excitation band: Simultaneous use of two sensitizers

Abstract

Articles you may be interested inDielectric controlled excited state relaxation pathways of a representative push-pull stilbene: A mechanistic study using femtosecond fluorescence up-conversion technique J. Chem. Phys. 138, 084308 (2013); 10.1063/1.4792933 Efficient organic light-emitting diodes through up-conversion from triplet to singlet excited states of exciplexes

Photochemical upconversion: present status and prospects for its application to solar energy conversion

“…Successful attempts to combine two or more porphyrin sensitizers providing triplets to the same emitter were presented above and mainly aim at extending the spectral harvest of the TTA system. 102,103 However, in contrast, employing more than one emitter species appears to yield a benefit in UC efficiency. First of all, the solubility problem can be mitigated if the sensitizer triplets are accepted by two separate species instead of one.…”

“…While the mentioned concept would in principle be applicable to TTA-UC materials as well, it appears more promising to employ combinations of multiple sensitizers whose combined absorption regions are staggered such that they straddle a larger region of the solar spectrum -a strategy first introduced by Baluschev et al, 102,103 which was shown to work with a single emitting species if the energy levels are correctly aligned. Broadening the upconvertor's spectral response through sensitization with semiconductor nanocrystals has been attempted, but this introduces reabsorption of upconverted light at the expense of a back-reflector.…”

“…However, it has already been demonstrated that a family of sensitizers can be combined with a single emitter species in such way that the sensitizer absorption bands are staggered in order to provide a quasi-continuous absorption band over more than 125 nm width. 102,103 In order to minimize parasitic absorption, the overlap between the emission band of the TTA emitter and the absorption bands of both emitter and sensitizer must be minimized. Figure 5 shows the situation for two TTA solutions employed in our studies, 47,93,95 plotted for typical concentrations.…”

Transition-Metal Complexes for Triplet–Triplet Annihilation-Based Energy Upconversion

“…The integral upconverted fluorescence of the acceptor by simultaneous excitation at two wavelengths (λ ¼ 695 nm for Pd-2 and λ ¼ 635 nm for Pd-3) was slightly more intense than the sum of the integral fluorescence for each single emitter/sensitizer system [30]. Then, A-6 as an acceptor with the sensitizer Pd-2 for TTA upconversion, a single-mode continuous-wave diode laser (λ ¼ 695 nm) was used as the excitation source, and the anti-Stokes shift was about 0.7 eV.…”

Efficient Broadband Triplet–Triplet Annihilation‐Assisted Photon Upconversion at Subsolar Irradiance in Fully Organic Systems

“…This concept was proposed for the fi rst time in 2007 by Baluschev and co-workers, who achieved NIR-to-vis conversion by exploiting two different sensitizers simultaneously excited by two lasers or by concentrated solar light (1 W cm −2 ), and only recently the same group developed a broadband absorption system probably because of a lack of suitable dyes available on the market. [ 29,30 ] Here, we have taken this approach to the extreme by synthesizing a full set of sensitizers that were designed ad hoc, and in which each sensitizer is able to transfer the harvested energy to the same emitter. In this way, we obtained an optimized sTTA-UC system with a continuous and broad absorption, which allowed achieving a QY UC as large as 10% under 1 sun of broadband non-coherent excitation light.…”