Sub-10-fs observation of bound exciton formation in organic optoelectronic devices

• Type: Article in International Scientific Journal
• Date: 2022

Authors

Maimaris, M (Author) Other; Pettipher, AJ (Author) Other; Azzouzi, M (Author) Other; Walke, DJ (Author) Other; Zheng, XJ (Author) Other; Gorodetsky, A (Author) Other; Dong, YF (Author) Other; Tuladhar, PS (Author) Other; Crespo, H (Author) FCUP; Nelson, J (Author) Other; Tisch, JWG (Author) Other; Bakulin, AA (Author) Other

Journal

Title: Nature Communications

Vol. 11 No. 3203

ISSN: 2041-1723

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 1 Citation

Scopus - 1 Citation

Other information

Authenticus ID: P-00X-2P9

DOI: 10.1038/s41467-022-32478-8

Abstract (EN): Ultrafast action spectroscopies of organic optoelectronic devices reveal that the formation of bound exciton state occurs as fast as 10 fs. Excitons having excess energy can dissociate spontaneously within 50-fs before acquiring bound character. 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.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10