Publisher's Note: Upconversion-induced fluorescence in multicomponent systems: Steady-state excitation power threshold [Phys. Rev. B78, 195112 (2008)]

Triplet transport in thin films: fundamentals and applications

“…Among reported upconversion methods, it is the only one that has demonstrated potential for harvesting incoherent photons from the sun without concentrators. Monguzzi et al proposed a figure of merit for TTA-based upconversion: 103 the threshold excitation intensity, I th , at which the efficiency of TTA is 0.5. They showed that:…”

Photon Upconversion on Dye-Sensitized Nanostructured ZrO2 Films

“…This pair of dye molecules was chosen because of their commercial availability and previously reported photon upconversion in solution 10 and in poly(methyl methacrylate) (PMMA) films 11 under low excitation light intensities. The surface properties and refractive index of ZrO 2 are comparable to those of TiO 2 , 12 but its conduction band is approximately 1.3 eV higher than that of TiO 2 , 13 thus excluding the possibility of electron injection from the singlet excited emitter into the semiconductor and, therefore, quenching of the upconverted emission.…”

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

“…For both samples, φ eff follows linearly the excitation intensity at low powers, and then saturates becoming independent of the excitation above the respective power thresholds. [ 24 ] In the case of the single sensitizer solution, the slope change occurs at I th = 2.1 × 10 17 ph cm −2 s −1 , while for the multisensitizer solution we measure a three-fold reduction of the threshold, I th = 6.5 × 10 16 . By considering the solar power distribution under AM 1.5 global conditions, the I th value measured for the multisensitizer system corresponds to a sub-solar irradiance (0.9 suns ).…”

“…As previously introduced, to quantify the irradiance at which the high excitation limit starts for sTTA-UC we must consider the excitation intensity threshold I th , which is the power density at which φ TTA is 0.5, which can be written as [ 24 ] I Z d…”

“…To date, the best amongst the proposed sensitizers are phosphorescent metalated porphyrins, which have electronic properties suitable for i) effi cient sensitization of the dark triplets of the highly fl uorescent emitters used in sTTA-UC systems, and ii) prevention of reabsorption of upconverted light, thanks to their large transparency windows in the absorption spectrum (Figure 1 b). [ 24 ] On the other side, the low-energy absorption peak of these porphyrins, which is exploited in the sTTA-UC, shows a typical bandwidth of 10-20 nm, allowing the harvesting of only a small fraction of the solar photons. [ 23 ] This is a crucial bottleneck, already faced in rare-earth based upconverters, that prevents the employment of sTTA-UC in real world applications.…”