The coherence time of sunlight in the context of natural and artificial light-harvesting

Abstract

The suggestion that quantum coherence might enhance biological processes such as photosynthesis is not only of fundamental importance but also leads to hopes of developing bio-inspired ‘green’ quantum technologies that mimic nature. A key question is how the timescale of coherent processes in molecular systems compare to that of the driving light source—the Sun. Across the quantum biology literature on light-harvesting, the coherence time quoted for sunlight spans about two orders of magnitude, ranging from 0.6 to ‘10s’ of femtoseconds. This difference can potentially be significant in deciding whether the induced light-matter coherence is long enough to affect dynamical processes following photoexcitation. Here we revisit the historic calculations of sunlight coherence starting with the black-body spectrum and then proceed to provide values for the more realistic case of atmospherically filtered light. We corroborate these values with interferometric measurements of the complex degree of temporal coherence from which we calculate the coherence time of atmospherically filtered sunlight as $$1.12\pm {0.04}\,{\hbox { fs}}$$ 1.12 ± 0.04 fs , as well as the coherence time in a chlorophyll analogous filtered case as $$4.87\pm {0.21}\,{\hbox { fs}}$$ 4.87 ± 0.21 fs .

Advanced VO2/Polymer Nanocomposite Smart Window Films Using VO2 Nanoparticles from High-Throughput Flow Synthesis

“…The absorption peaks for the NLETS are observed at 710 and 760 nm. The additional thermochromic system can boost the overall modulation of solar energy by ∼12%, with the solar radiance having a more significant effect in the visible light region . The second thermochromic system with our PFDA-coated VO 2 nanoparticles successfully improved the SM to 19.90% with the Δ T lum value at 38.45%.…”

“…The additional thermochromic system can boost the overall modulation of solar energy by ∼12%, with the solar radiance having a more significant effect in the visible light region. 63 The second thermochromic system with our PFDAcoated VO 2 nanoparticles successfully improved the SM to 19.90% with the ΔT lum value at 38.45%. The significance of secondary thermochromic materials allows for boosted thermochromic performance without interfering with the VO 2 nanoparticles and provides a more suitable color for daily use.…”

Light-Harvesting Efficiency Cannot Depend on Optical Coherence in the Absence of Orientational Order

“…This implies the requirement that T ≫ τ coh , the coherence time of the light, in agreement with earlier results. 31 For sunlight, τ coh ∼ 1 fs, 40 and for lasers, τ coh can reach 10 s, 41 both of which are much shorter than the days or years over which the performance of light-harvesting systems is typically evaluated.…”

Measuring Charge Carrier Lifetime in Solar Cells Using Pulsed Diode Laser and Terahertz Spectroscopy

“…Traditional THz carrier lifetime measurements use a femtosecond laser as the excitation source, and the reason for testing the steady-state measurement is that we introduced a new optical pump (ThorLabs LDC205C & ThorLabs LDM56 laser diode) to the setup. With the new profile of light sources such as their wavelength or the light intensity, it is necessary to check if charge carrier dynamics behave as expected [15].…”