Fundamental mechanisms underlying exciton formation in organic semiconductors are complex and elusive as it occurs on ultrashort sub-100-fs timescales. Some fundamental aspects of this process, such as the evolution of exciton binding energy, have not been resolved in time experimentally. Here, we apply a combination of sub-10-fs Pump-Push-Photocurrent, Pump-Push-Photoluminescence, and Pump-Probe spectroscopies to polyfluorene devices to track the ultrafast formation of excitons. While Pump-Probe is sensitive to the total concentration of excited states, Pump-Push-Photocurrent and Pump-Push-Photoluminescence are sensitive to bound states only, providing access to exciton binding dynamics. We find that excitons created by near-absorption-edge photons are intrinsically bound states, or become such within 10 fs after excitation. Meanwhile, excitons with a modest >0.3 eV excess energy can dissociate spontaneously within 50 fs before acquiring bound character. These conclusions are supported by excited-state molecular dynamics simulations and a global kinetic model which quantitatively reproduce experimental data.
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http://dx.doi.org/10.1038/s41467-022-32478-8 | DOI Listing |
Adv Sci (Weinh)
December 2024
Center on Nanoenergy Research, Carbon Peak and Neutrality Science and Technology Development Institute, School of Physical Science & Technology, Guangxi University, Nanning, 530004, China.
Nonfullerene acceptors are critical in advancing the performance of organic solar cells. However, unfavorable morphology and low photon-to-electron conversion in the acceptor range continue to limit the photocurrent generation and overall device performance. Herein, benzoic anhydride, a low-cost polar molecule with excellent synergistic properties, is introduced in combination with the traditional additive 1-chloronaphthalene to optimize the aggregation of nonfullerene acceptors.
View Article and Find Full Text PDFSmall
December 2024
Institute of Polymer Optoelectronic Materials & Devices, Guangdong Basic Research Center of Excellence for Energy & Information Polymer Materials, State Key Laboratory of Luminescent Materials & Devices, South China University of Technology, Guangzhou, 510640, China.
Polymer hole transport materials offer significant efficiency and stability advantages for p-i-n perovskite solar cells. However, the energetic disorder of amorphous polymer hole transport materials not only limits carrier transport but also impedes contact between the polymer and perovskite, hindering the formation of high crystalline quality perovskites. Herein, a novel low energetic disordered polymer hole transport material, PF8ICz, featuring an indeno[3,2-b]carbazole unit with extended π-conjugation is designed and synthesized.
View Article and Find Full Text PDFNano Lett
December 2024
School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022, P. R. China.
Room-temperature phosphorescent (RTP) carbon dots (CDs) demonstrate significant potential applications in the field of information anticounterfeiting due to their excellent optical properties. However, RTP emission of CDs remains significantly limited due to the spin-forbidden properties of triplet exciton transitions. In this work, an in situ nitrogen doping strategy was employed to design and construct strong spin-orbit coupling nitrogen-doped CDs with mesoporous silica with alumina (N-CDs@MS@AlO) RTP composites.
View Article and Find Full Text PDFChemosphere
December 2024
Centre for Nanoscience and Nanotechnology, Jamia Millia Islamia, New Delhi, 110025, India. Electronic address:
In this study, a novel 2D/2D nanocomposite of MXene and VO was synthesized using a facile hydrothermal approach for the efficient removal of crystal violet (CV), a textile dye from contaminated water to achieve Sustainable Development Goal (SDG) 14; "Save Lives Below Water". Here, the catalytic performance of pristine MXene was prominently boosted with the introduction of ball milled VO as an electron generating agent. The degradation efficiency of synthesized nanocomposite significantly enhanced from 57 % to 92 %, 41 % - 76 % and 7 % - 58 % with an error of ±2 % as compared to pristine MXene at 10, 20 and 30 ppm concentrations of CV, respectively.
View Article and Find Full Text PDFSci Adv
December 2024
Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA.
A fundamental requirement for photonic technologies is the ability to control the confinement and propagation of light. Widely used platforms include two-dimensional (2D) optical microcavities in which electromagnetic waves are confined in either metallic or distributed Bragg reflectors. Recently, transition metal dichalcogenides hosting tightly bound excitons with high optical quality have emerged as promising atomically thin mirrors.
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