Ultrafast Excited-State Dynamics of all-trans-Capsanthin in Organic Solvents

Abstract

The C carotenoid capsanthin is of photophysical interest because it belongs to the family of terminally carbonyl-substituted apocarotenes. These have the potential to exhibit intramolecular charge transfer (ICT) character in the excited state. We studied its ultrafast dynamics in different solvents using broadband transient absorption spectroscopy in the 260-1600 nm range. Photoexcitation initially populated the S(1B) state which decayed to the S(2A) state in 120-150 fs. The lifetime of the S state decreased from 10.3 ps (isooctane) to 9.1 ps (methanol). Together with the absence of stimulated emission this suggested a weak ICT character of S. A steric influence of the five-membered ring in capsanthin was identified based on a comparison with the sister apocarotenone citranaxanthin which features methyl substitution at the keto group. While both apocarotenones exhibit the same S lifetime in isooctane, the decrease in lifetime in polar solvents is weaker for capsanthin because presumably the five-membered ring sterically perturbs stabilization of ICT character by the solvent. For the S state of capsanthin we further observed intramolecular vibrational redistribution and collisional energy transfer to the solvent with time constants of 340-420 fs and 8.5-9.1 ps, respectively. No evidence for excited-state photoisomerization of capsanthin was found.

Enhanced On–Off Ratio Photodetectors Based on Lead‐Free Cs3Bi2I9 Single Crystal Thin Films

“…The recorded transient profiles were shown in Figure a,b and Figure S5 (Supporting Information). A typical oscillatory triple‐peak signal was shown up with a negative peak at 488 nm, which can be assigned to the relaxed carriers at the indirect band edge 32,41. The bleach kinetic at 488 nm was monitored and further analyzed by a single exponential fitting mode, as displayed in Figure 4c.…”

Effects of annealing temperature on photovoltaic properties of lead-free (CH₃NH₃)₃Bi₂I₉ solar cells

“…33) All diffraction reflections could be indexed as a hexagonal (CH 3 NH 3 ) 3 Bi 2 I 9 with space group P6 3 /mmc. 34) The (CH 3 NH 3 ) 3 Bi 2 I 9 layers annealed at 120140 °C were randomly oriented. On the other hand, 002, 004, and 006 diffraction reflections at 7.9, 16.1, and 24.4°, respectively, were observed for the film annealed at 150 °C.…”

From Pb to Bi: A Promising Family of Pb‐Free Optoelectronic Materials and Devices

“…Besides, Miyasaka et al investigated different device structures, e.g., anatase or brookite TiO 2 as the mesoscopic scaffold and planar structure, correspondingly. They found that the physical junction was poorly formed and MA 3 Bi 2 I 9 film was nonuniform on brookite TiO 2 and planar substrates, in accordance with the conclusion made by Lenzer et al that MA 3 Bi 2 I 9 should employed bulk heterojunction architecture to render the efficient carrier separation. Considering its absorbance edge of 620 nm, the highest J sc would be 10 mA cm −2 .…”