ORCID Profile
0000-0002-2359-1304
Current Organisation
University of Adelaide
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Publisher: University of Adelaide
Date: 2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7NR05247B
Abstract: The carrier dynamics of lead sulphide quantum dot (PbS QD) drop cast films and closely packed ordered Langmuir–Blodgett films are studied with ultra-fast femtosecond transient absorption spectroscopy.
Publisher: American Chemical Society (ACS)
Date: 14-10-2016
Publisher: American Chemical Society (ACS)
Date: 15-05-2023
Publisher: American Chemical Society (ACS)
Date: 24-09-2018
Publisher: American Chemical Society (ACS)
Date: 19-02-2019
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0CE01505A
Abstract: Materials in which charge delocalization and migration can be tuned are critical for electronic applications.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9NR04787E
Abstract: The green fluorescence of CsPbBr 3 –Cs 4 PbBr 6 perovskite composites is ascribed to the emissions of band-edge and the defect trapped exciton of CsPbBr 3 .
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2CP03858G
Abstract: The search for quantum behaviour within a BODIPY light-harvesting complex reveals coherent oscillations at 100 cm −1 and 600 cm −1 .
Publisher: Springer Science and Business Media LLC
Date: 22-01-2018
DOI: 10.1038/NCHEM.2926
Abstract: Singlet fission is a process whereby two triplet excitons can be produced from one photon, potentially increasing the efficiency of photovoltaic devices. Endothermic singlet fission is desired for a maximum energy-conversion efficiency, and such systems have been considered to form an excimer-like state with multiexcitonic character prior to the appearance of triplets. However, the role of the excimer as an intermediate has, until now, been unclear. Here we show, using 5,12-bis((triisopropylsilyl)ethynyl)tetracene in solution as a prototypical ex le, that, rather than acting as an intermediate, the excimer serves to trap excited states to the detriment of singlet-fission yield. We clearly demonstrate that singlet fission and its conjugate process, triplet-triplet annihilation, occur at a longer intermolecular distance than an excimer intermediate would impute. These results establish that an endothermic singlet-fission material must be designed to avoid excimer formation, thus allowing singlet fission to reach its full potential in enhancing photovoltaic energy conversion.
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2CP01943D
Abstract: Time-resolved polarisation anisotropy and Monte Carlo simulations show that singlet fission preserves polarisation correlation between photons absorbed and emitted by a material through removing excitons decorrelated by migration.
Publisher: American Chemical Society (ACS)
Date: 11-03-2014
DOI: 10.1021/JZ500217F
Abstract: The dynamics of high-energy excitons of poly(3-hexylthiophene) (P3HT) are shown to consist of torsional relaxation and exciton dissociation to form free carriers. In this work, we use pump-push-probe femtosecond transient absorption spectroscopy to study the highly excited states of P3HT in solution. P3HT excitons are generated using a pump pulse (400 nm) and allowed to relax to the lowest-lying excited state before re-excitation using a push pulse (900 or 1200 nm), producing high-energy excitons that decay back to the original excited state with both subpicosecond (0.16 ps) and picosecond (2.4 ps) time constants. These dynamics are consistent with P3HT torsional relaxation, with the 0.16 ps time constant assigned to ultrafast inertial torsional relaxation. Additionally, the signal exhibits an incomplete recovery, indicating dissociation of high-energy excitons to form charge carriers due to excitation by the push pulse. Our analysis indicates that charge carriers are formed with a yield of 11%.
Publisher: Wiley
Date: 30-04-2019
Publisher: AIP Publishing
Date: 07-2021
DOI: 10.1063/5.0055528
Abstract: TIPS-pentacene is a small-molecule organic semiconductor that is widely used in optoelectronic devices. It has been studied intensely owing to its ability to undergo singlet fission. In this study, we aim to develop further understanding of the coupling between the electronic and nuclear degrees of freedom of TIPS-pentacene (TIPS-Pn). We measured and analyzed the 2D electronic spectra of TIPS-Pn in solutions. Using center line slope (CLS) analysis, we characterized the frequency-fluctuation correlation function of the 0–0 vibronic transition. Strong oscillations in the CLS values were observed for up to 5 ps with a frequency of 264 cm−1, which are attributable to a large vibronic coupling with the TIPS-Pn ring-breathing vibrational mode. In addition, detailed analysis of the CLS values allowed us to retrieve two spectral diffusion lifetimes, which are attributed to the inertial and diffusive dynamics of solvent molecules. Amplitude beating analysis also uncovered couplings with another vibrational mode at 1173 cm−1. The experimental results can be described using the displaced harmonic oscillator model. By comparing the CLS values of the simulated data with the experimental CLS values, we estimated a Huang–Rhys factor of 0.1 for the ring-breathing vibrational mode. The results demonstrated how CLS analysis can be a useful method for characterizing the strength of vibronic coupling.
Publisher: American Chemical Society (ACS)
Date: 13-01-2020
Abstract: In two-dimensional electronic spectroscopy (2DES), precise control of the arrival time of ultrashort laser pulses is critical to correlating the molecular states that are accessed in the experiment. In this work, we demonstrate a 2D electronic spectrometer design with an interferometric phase stability of ∼λ/250 at 600 nm. First, we present a new method for controlling pulse delay times based on transmission through pairs of optical flats rotated perpendicular to the beam propagation direction. Second, the calibration methods required to achieve adequate timing precision are also reported. Compared to existing designs using translating wedges, the rotating optical flats can achieve equivalent optical delay with a shorter path length in glass, reducing errors due to spectral dispersion of the broadband laser pulses used in 2DES. Our approach presents a simple, low-cost technique for multidimensional optical spectroscopy that is capable of resolving complex light-induced dynamics.
Publisher: American Chemical Society (ACS)
Date: 09-06-2017
DOI: 10.1021/ACS.JPCLETT.7B01053
Abstract: The excited states of conjugated polymers play a central role in their applications in organic solar photovoltaics. The delocalized excited states of conjugated polymers are short-lived (τ < 40 fs) but are imperative in the photovoltaic properties of these materials. Photoexcitation of poly(3-hexylthiophene) (P3HT) induces an excited-state absorption band, but the transitions that are involved are not well understood. In this work, calculations have been performed on P3HT analogues using nonlinear response time-dependent density functional theory to show that an increase in the oligomer length correlates with the dominance of the S
Publisher: AIP Publishing
Date: 26-08-2022
DOI: 10.1063/5.0100619
Abstract: Singlet fission (SF), a process that produces two triplet excitons from one singlet exciton, has attracted recent interest for its potential to circumvent the detailed-balance efficiency limit of single-junction solar cells. For the potential of SF to be fully realized, accurate assignment and quantification of SF is necessary. Intersystem crossing (ISC) is another process of singlet to triplet conversion that is important to distinguish from SF to avoid either over- or under-estimation of SF triplet production. Here, we quantify an upper bound on the rate of ISC in two commonly studied SF chromophores, TIPS–pentacene and TIPS–tetracene, by using transient absorption spectroscopy of solutions of varying concentrations in toluene. We show that SF in solutions of these acenes has previously been misidentified as ISC, and vice versa. By determining a bimolecular SF rate constant in concentrated solutions in which SF dominates over ISC, we distinguish triplet formation due to SF from triplet formation due to ISC and show that the characteristic time scale of ISC must be longer than 325 ns in TIPS–pentacene, while it must be longer than 118 ns in TIPS–tetracene. We additionally note that no excimer formation is observed in the relatively dilute (up to 8 mM) solutions studied here, indicating that previous excimer formation observed at much higher concentrations may be partially due to aggregate formation. This work highlights that an accurate quantification of ISC is crucial as it leads to accurate determination of SF rate constants and yields.
Publisher: Wiley
Date: 14-08-2017
Publisher: Springer Science and Business Media LLC
Date: 20-01-2017
DOI: 10.1038/NCOMMS14120
Abstract: The hot-phonon bottleneck effect in lead-halide perovskites (APbX 3 ) prolongs the cooling period of hot charge carriers, an effect that could be used in the next-generation photovoltaics devices. Using ultrafast optical characterization and first-principle calculations, four kinds of lead-halide perovskites (A=FA + /MA + /Cs + , X=I − /Br − ) are compared in this study to reveal the carrier-phonon dynamics within. Here we show a stronger phonon bottleneck effect in hybrid perovskites than in their inorganic counterparts. Compared with the caesium-based system, a 10 times slower carrier-phonon relaxation rate is observed in FAPbI 3 . The up-conversion of low-energy phonons is proposed to be responsible for the bottleneck effect. The presence of organic cations introduces overlapping phonon branches and facilitates the up-transition of low-energy modes. The blocking of phonon propagation associated with an ultralow thermal conductivity of the material also increases the overall up-conversion efficiency. This result also suggests a new and general method for achieving long-lived hot carriers in materials.
Publisher: Wiley
Date: 20-08-2019
Publisher: American Chemical Society (ACS)
Date: 17-01-2019
Publisher: American Chemical Society (ACS)
Date: 19-03-2015
No related grants have been discovered for Patrick Tapping.