PDF Publication Title:
Text from PDF Page: 005
SCIENCE ADVANCES | RESEARCH ARTICLE slightly more than N1/2. For the region between A2 and A3, the average scaling of falls between N0 and N−1/2, Emax between N2 and N0, and Pmax between N2 and N1/2. As A2 is further into the coupling- dominated regime than A3 is into the decay-dominated regime, the average scaling values between A2 and A3 are skewed toward the coupling-dominated scalings. B1 and B2 operate in the crossover regime, with an average scaling with N that is between the decay- dominated and coupling-dominated scalings, as reflected in Table 1. Discussion We have provided direct experimental evidence of superextensive energy storage capacity and charging in an organic microcavity by using ultrafast optical spectroscopy. Our realization of a prototype Dicke QB highlights the fact that purely closed unitary dynamics is insufficient for realizing a practical QB. The retention of energy re- quires finely tuned decoherence processes, allowing the battery to charge quickly and yet discharge much more slowly. This stabiliza- tion of stored energy is a key step to exploit superextensive charging. Our observation of dephasing shows that realistic noisy environments can aid the implementation and application of useful QBs. A chal- lenge for future work is to explore further how concepts of ratchet states could keep a QB operating in the range of higher-lying energy states that are associated with maximum absorption enhancement, i.e., near the midpoint of the Dicke ladder (37). We conclude by discussing the potential for future applications based on superextensive charging. One practical challenge noted above is that quenching limits the performance of the QB at high concentrations. Overcoming this limitation requires careful choice of materials to suppress intermolecular quenching. We note that there are classes of materials where quenching is particularly sup- pressed. For example, in proteins such as green fluorescent protein (38), the active chromophore is surrounded by a cage, which suppresses exciton-exciton quenching at high intensities. These materials might provide a route to allow the study of higher concen- trations. Beyond energy storage, the key challenge for practical ap- plications of this effect is its integration in devices where energy can be efficiently extracted and used. While our focus has been on the quantum advantage in charging, there do exist approaches to effi- ciently extract energy. For example, this may be achieved by including charge transport layers between the active layer and the cavity layers (39). The transport layers allow charge separation of the excitons as well as preventing recombination. This transforms the top cavity layer into a cathode and the bottom cavity into an anode, giving rise to an electric current. Hence, our work provides a direct path for the integration of the superextensive energy absorption process in an organic photovoltaic device. The fast dynamics of such a device may also be useful as an optical sensor in low-light conditions or poten- tially for energy harvesting applications (40–43). More generally, the idea of superextensive charging may have wide-reaching conse- quences for sensing and energy capture and storage technologies. MATERIALS AND METHODS Device fabrication The microcavities constructed consist of a thin layer of LFO (Kremer Pigmente) dispersed in a PS (Sigma-Aldrich; average mo- lecular weight of ~192,000) matrix. The bottom DBR consisted of 10 pairs of SiO2/Nb2O5 and were fabricated using a mixture of thermal evaporation and ion-assisted electron beam deposition by Quach et al., Sci. Adv. 8, eabk3160 (2022) 14 January 2022 Helia Photonics Ltd. Solutions of LFO dissolved in PS (25 mg/ml) in dichloromethane were prepared at 0.5, 1, 5, and 10% concentra- tion by mass. Each LFO solution was then spin coated on top of the bottom DBR to produce a thin film with an approximate thickness of 185 nm. An eight-pair DBR was then deposited on top of the LFO layer using electron beam deposition. With this pair of mirrors, the reflectivity was >99% in the spectral region of interest (44). The diluted molecules are expected to be isolated at a low con- centration of 0.1 to 1%, but at higher dye concentrations, the 0-0 emission transition red-shifts by a few nanometers, and the second peak increases in intensity because of aggregation of the dye mole- cules. This is evident in fig. S2 (A and B), with additional broader features observed at longer wavelengths, which we assign to inter- molecular states such as excimers. The 0.5 and 1% cavities lie in the weak coupling regime, i.e., no polaritonic splitting could be seen in the cavity reflectivity spectrum, as shown in fig. S2. For the 5% cavity, we see a weak anticrossing feature in the reflectivity spectrum (a small kink near the crossing), indicating operation in the intermediate coupling regime. The 10% cavity operated in the strong coupling regime, showing a Rabi split- ting of around 100 meV around the 0-0 transition (along with inter- mediate coupling between the cavity mode and the 0-1 transition). Figure S3 shows a transfer matrix simulation of the electric field dis- tribution of the 1% cavity (the cavities exhibit similar distributions). Pump-probe spectroscopy Probe and pump pulses were generated by a NOPA. The NOPA was pumped by a fraction (450 J) of the laser beam generated by a re- generatively amplified Ti:Sapphire laser (Coherent Libra) produc- ing 100-fs pulses at 800 nm at a repetition rate of 1 kHz. A pair of chirped mirrors were placed at the output of the NOPA to compensate for temporal dispersion, and by using seven “bounces,” we were able to generate pulses with a temporal width below 20 fs. The laser beam was then split by a beam splitter, with the probe being delayed via a translation stage and the pump being modulated mechanically using a chopper at 500 Hz. Lindblad master equation As noted above, we find that the experimental behavior is well re- produced by the dynamics of the Dicke model, a model of a micro- cavity photon mode coupled to TLSs representing the molecules. As further discussed in the Supplementary Materials, such a model is generally an approximation for organic molecules but for some sys- tems can become a very accurate approximation in the limit of low temperatures (45). The open driven nature of the experimental system is modeled with the Lindblad master equation i Nzz−− ̇ (t)=−─[H(t),(t)]+∑( L[]+ L[ ])+L[a] (2) where(t)isthedensitymatrix,andL[O]≡OO − O O− O O is the Lindbladian superoperator. a† and a are the cavity photon creation and annihilation operators, and xj ,y,z are the Pauli spin matrices for each molecule, with the raising and lowering spin operators defined as ±j = (xj ± i yj )/2. There are three decay chan- nels corresponding to the cavity decay (), dephasing (z), and relaxation rate (−) of the individual TLSs. The Hamiltonian for the LFO molecules in cavity is modeled as a collection of noninteracting TLSs with characteristic frequency equal to that of the cavity ħ j=1 j j † 1_2 † 1_2 † 5 of 7 Downloaded from https://www.science.org on June 26, 2022PDF Image | Superabsorption organic microcavity Toward a quantum battery
PDF Search Title:
Superabsorption organic microcavity Toward a quantum batteryOriginal File Name Searched:
sciadvabk3160.pdfDIY PDF Search: Google It | Yahoo | Bing
Sulfur Deposition on Carbon Nanofibers using Supercritical CO2 Sulfur Deposition on Carbon Nanofibers using Supercritical CO2. Gamma sulfur also known as mother of pearl sulfur and nacreous sulfur... More Info
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)