- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Molecular vibrations reduce the maximum achievable photovoltage in organic solar cells
摘要： The low-energy edge of optical absorption spectra is critical for the performance of solar cells, but is not well understood in the case of organic solar cells (OSCs). We study the microscopic origin of exciton bands in molecular blends and investigate their role in OSCs. We simulate the temperature dependence of the excitonic density of states and low-energy absorption features, including low-frequency molecular vibrations and multi-exciton hybridisation. For model donor-acceptor blends featuring charge-transfer excitons, our simulations agree very well with temperature-dependent experimental absorption spectra. We unveil that the quantum effect of zero-point vibrations, mediated by electron-phonon interaction, causes a substantial exciton bandwidth and reduces the open-circuit voltage, which is predicted from electronic and vibronic molecular parameters. This effect is surprisingly strong at room temperature and can substantially limit the OSC’s efficiency. Strategies to reduce these vibration-induced voltage losses are discussed for a larger set of systems and different heterojunction geometries.
关键词： molecular vibrations,exciton bands,electron-phonon interaction,organic solar cells,photovoltage
更新于2025-09-23 15:19:57
-
Formation of thioglucoside single crystals by coherent molecular vibrational excitation using a 10-fs laser pulse
摘要： Compound crystallization is typically achieved from supersaturated solutions over time, through melting, or via sublimation. Here a new method to generate a single crystal of thioglucoside using a sub-10-fs pulse laser is presented. By focusing the laser pulse on a solution in a glass cell, a single crystal is deposited at the edge of the ceiling of the glass cell. This finding contrasts other non-photochemical laser-induced nucleation studies, which report that the nucleation sites are in the solution or at the air-solution interface, implying the present crystallization mechanism is different. Irradiation with the sub-10-fs laser pulse does not heat the solution but excites coherent molecular vibrations that evaporate the solution. Then, the evaporated solution is thought to be deposited on the glass wall. This method can form crystals even from unsaturated solutions, and the formed crystal does not include any solvent, allowing the formation of a pure crystal suitable for structural analysis, even from a minute amount of sample solution.
关键词： crystallization,coherent molecular vibrations,single crystal,thioglucoside,laser-induced nucleation
更新于2025-09-19 17:13:59
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Field-Resolved Infrared Spectroscopy of Human Blood to Tackle Lung, Prostate and Breast Cancer Detection
摘要： Broadband mid-infrared spectroscopy of biofluids carries great potential for biological and biomedical applications, as it provides fast, reliable and label-free access to the molecular composition of the sample. When applied to human blood serum, a range of molecular contents can be quantified and specific changes in the absorption spectra, driven by diseases (e.g. cancer) can be identified and used for diagnostic purposes. One remaining challenge is the complexity of human serum: physiological phenotypes are driven by minor changes in concentration of thousands of different molecules. At the same time, although many low-abundance molecules are very informative for disease detection, these are often not detectable with conventional Fourier-Transform Infrared (FTIR) spectroscopy and quantum-cascade laser (QCL) based approaches due to a lack of sensitivity and specificity. Here we show how field-resolved spectroscopy (FRS) of few-cycle-excited molecular vibrations can be utilised to address these shortcomings and demonstrate its applicability for the measurement of human blood serum in a clinical setting. In a preparatory experiment, we quantitatively investigate the ability of FRS to detect small changes in the sample response by spiking blood serum with a defined concentration of dimethyl sulfone (DMSO2). We demonstrate that FRS is able to detect changes in molecular concentration down to the sub-μg/ml level in human blood serum, outperforming the sensitivity of FTIR- and QCL-based approaches. Hence, the smallest changes currently detectable by FRS are five orders of magnitude below the concentration of the most highly-abundant molecules in blood, implying a detectable concentration dynamic range of 105. Based on these results, we apply FRS for the first time in a real-world setting, a clinical study with a well-matched cohort of 195 control individuals and 58 lung, 41 prostate and 42 breast cancer patients and compare the obtained results to state-of-the-art FTIR measurements of the same samples. Corresponding infrared molecular fingerprints were recorded as time-domain sampled field oscillations emerging from the excited molecules in the serum samples (Fig. 1a). We find that investigation at different time windows (Fig. 1c-d) reveals a distinct temporal response of the samples originating from controls as compared to lung cancer patients. Preliminary analysis of the time-domain data with a random forest classifier reveals a high detection accuracy for cancer detection. Even though FRS, in this early stage of development, has considerably smaller spectral coverage as compared to FTIR, it reaches a similar rate of cancer detection efficiency. This suggests that the next generation FRS, with several octave spectral coverage, holds promise for outperforming FTIR fingerprinting substantially.
关键词： cancer detection,molecular vibrations,field-resolved spectroscopy,infrared spectroscopy,human blood
更新于2025-09-11 14:15:04
-
Quantitative mobility evaluation of organic semiconductors using quantum dynamics based on density functional theory
摘要： We present an order-N methodology to evaluate mobilities of charge carriers coupled with molecular vibrations using quantum dynamics based on first-principles calculations that can be applied to micron-scale soft materials. As a demonstration, we apply it to several organic semiconductors and show that the calculated intrinsic hole mobilities and their temperature dependences are quantitatively in good agreement with those obtained in experiments. We also clarified which vibrational modes dominate the transport properties. The methodology paves the way for quantitative prediction of the transport properties of various soft materials.
关键词： quantum dynamics,density functional theory,charge-carrier mobility,organic semiconductors,molecular vibrations
更新于2025-09-04 15:30:14