The effect of the substrate on photothermal deflection spectroscopy measurements of optical absorption in a-Si:H

Rodley, David; Jones, D. I.; Stewart, A. D.

doi:10.1080/09500838908206336

Cited by 9 publications

(2 citation statements)

References 10 publications

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“…In this report, dark-state energies are assessed in two ways. Experimentally, the assessment is through highly sensitive photothermal deflection spectroscopy (PDS) measurements of energy dissipation resulting from optical excitation − in concentrated carotenoid filmsexpected to feature robust conformational disorder in the ground state. Computationally, the assessment is through multireference perturbation theory (MRPT) with the density matrix renormalization group (DMRG) − so as to investigate the impact of bond-length alternation on the manifold of states.…”

Section: Introductionmentioning

confidence: 99%

Carotenoid Nuclear Reorganization and Interplay of Bright and Dark Excited States

et al. 2019

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We report quantum chemical calculations using multireference perturbation theory (MRPT) with the density matrix renormalization group (DMRG) plus photothermal deflection spectroscopy measurements to investigate the manifold of carotenoid excited states and establish their energies relative to the bright state (S 2 ) as a function of nuclear reorganization. We conclude that the primary photophysics and function of carotenoids are determined by interplay of only the bright (S 2 ) and lowest-energy dark (S 1 ) states. The lowest-lying dark state, far from being energetically distinguishable from the lowest-lying bright state along the entire excited-state nuclear reorganization pathway, is instead computed to be either the second or first excited state depending on what equilibrium geometry is considered. This result suggests that, rather than there being a dark intermediate excited state bridging a non-negligible energy gap from the lowestlying dark state to the lowest-lying bright state, there is in fact no appreciable energy gap to bridge following photoexcitation. Instead, excited-state nuclear reorganization constitutes the bridge from S 2 to S 1 , in the sense that these two states attain energetic degeneracy along this pathway.

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Section: Introductionmentioning

confidence: 99%

Carotenoid Nuclear Reorganization and Interplay of Bright and Dark Excited States

et al. 2019

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“…The higher value for the lc-Si:H sample can be attributed to the coexistence of amorphous and crystalline phases in it. The defect related absorption a 0 at E g 1.3 eV of both untreated (flat) samples levels out at a 0 % 10 1 cm À1 , indicating that the PDS measurements have been partially affected by additional glass substrate absorption at long wavelengths, 23 which was not avoided in our experiment. This assumption is supported by ESR measurements of the untreated (flat) a-Si:H samples, which show dangling bond densities of about 10 16 cm À3 , corresponding to an optical absorption coefficient at 1.3 eV of a 0 % 10 0 cm À1 .…”

Section: B Photothermal Deflection Spectroscopymentioning

confidence: 91%

Black thin film silicon

Koynov

Brandt

Stutzmann

2011

Journal of Applied Physics

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“Black etching” has been proposed previously as a method for the nanoscale texturing of silicon surfaces, which results in an almost complete suppression of reflectivity in the spectral range of absorption relevant for photovoltaics. The method modifies the topmost 150 to 300 nm of the material and thus also is applicable for thin films of silicon. The present work is focused on the optical effects induced by the black-etching treatment on hydrogenated amorphous and microcrystalline silicon thin films, in particular with respect to their application in solar cells. In addition to a strong reduction of the reflectivity, efficient light trapping within the modified thin films is found. The enhancement of the optical absorption due to the light trapping is investigated via photometric measurements and photothermal deflection spectroscopy. The correlation of the texture morphology (characterized via atomic force microscopy) with the optical effects is discussed in terms of an effective medium with gradually varying optical density and in the framework of the theory of statistical light trapping. Photoconductivity spectra directly show that the light trapping causes a significant prolongation of the light path within the black silicon films by up to 15 μm for ∼1 μm thick films, leading to a significant increase of the absorption in the red.

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Optical absorption of high quality a-Si:H and a-SixN1−x:H in the low energy region 0.43 eV ≈1.5 eV by PDS

Nonomura

Nishiwaki

Kusakabe

et al. 1993

Journal of Non-Crystalline Solids

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The effect of the substrate on photothermal deflection spectroscopy measurements of optical absorption in a-Si:H

Cited by 9 publications

References 10 publications

Carotenoid Nuclear Reorganization and Interplay of Bright and Dark Excited States

Carotenoid Nuclear Reorganization and Interplay of Bright and Dark Excited States

Black thin film silicon

Optical absorption of high quality a-Si:H and a-SixN1−x:H in the low energy region 0.43 eV ≈1.5 eV by PDS

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