Microscopic Insights into Surface Molecular Doping of Small-Molecule OSCs for OFETs

Esther Barrena^a

^aMaterials Science Institute of Barcelona (ICMAB-CSIC), Barcelona, Spain

Proceedings of MATSUS Spring 2026 Conference (MATSUSSpring26)

B3 Chemical and Electrochemical Doping of Organic Semiconductors

Barcelona, Spain, 2026 March 23rd - 27th

Organizers: Mariano Campoy Quiles and Christian Müller

Invited Speaker, Esther Barrena, presentation 138
Publication date: 15th December 2025

This work presents a comprehensive structural and electronic investigation of surface molecular doping in molecular doping in small-molecule organic semiconductor thin films for organic field-effect transistor (OFET), by using two electron acceptor molecules (F6TCNNQ and C60F48) molecular dopants. We present several studies with pentacene [1,2] and benzothieno[3,2-b][1]benzothiophene (BTBT) derivatives [3-6], demonstrating that the nature of OSC side groups in BTBT or the quality of pentacene packing at nanoscopic level influences the nucleation, ordering and distribution of the acceptor onto the OSC surface On the other hand, the shape of the acceptor molecule (planar F6TCNNQ and bulky C60F48) has a profound impact on the doping mechanism (charge transfer vs. charge-transfer-complex formation) and the structural properties of the formed heterojunction. The implications for the performance and stability of the devices is also discussed. Collectively, these studies provide a microscopic view on the formation of the acceptor/OSC interfaces and the associated electronic effects.

References:

[1] F. Silvestri, M.J. Prieto, A. Babuji, L.C. Tănase, L. de Souza Caldas, O. Solomeshch, Th. Schmidt, C. Ocal, E. Barrena, Impact of Nanomorphology on Surface Doping of Organic Semiconductors: The Pentacene−C60F48 Interface, ACS Appl. Mater. Interfaces 12, 22, 25444–25452 (2020)

[2] F. Silvestri, L. Pithan, A. Babuji, C. Ocal, E. Barrena, Design Dependence of the Interface Structure and Crystalline Order of Organic Semiconductor/Dopant Heterojunctions: Pentacene/C60F48 J. Phys. Chem. C, 125, 9, 5363–5371 (2021)

[3] A. Babuji, I. Temiño, A. Pérez-Rodríguez, O. Solomeshch, N. Tessler, M. Vila, J. Li, M. Mas-Torrent, C. Ocal, E. Barrena, “Double Beneficial Role of Fluorinated Fullerene Dopants on Organic Thin Film Transistors: Structural Stability and Improved Performance” ACS Appl. Mater. Interfaces, 25, 28416 (2020) A. Babuji, I. Temiño, A. Pérez-Rodríguez, O. Solomeshch, N. Tessler, M. Vila, J. Li, M. Mas-Torrent, C. Ocal, E. Barrena, “Double Beneficial Role of Fluorinated Fullerene Dopants on Organic Thin Film Transistors: Structural Stability and Improved Performance” ACS Appl. Mater. Interfaces, 25, 28416 (2020)

[4] A. Babuji, A. Cazorla, E. Solano, C. Habenicht, H. Kleemann, C. Ocal, K. Leo, E. Barrena “Charge-Transfer Complexes in Organic Field-Effect Transistors: Superior Suitability for Surface Doping” ACS Appl. Mater. Interfaces 14, 39, 44632–44641 (2022).

[5] J. Li, A. Babuji, I. Temiño, T. Salzillo, F. D’Amico, R. Pfattner, C. Ocal, E. Barrena*, M. Mas-Torrent “Chemical Doping of the Organic Semiconductor C8-BTBT-C8 Using an Aqueous Iodine Solution for Device Mobility Enhancement” Adv. Mat. Technol. 2101535 (2022).

[6] A. Babuji, F. Silvestri, L. Pithan, A. Richard, Y. H. Geerts, N. Tessler, O. Solomeshch, C. Ocal, E. Barrena* “Effect of the Organic Semiconductor Side Groups on the Structural and Electronic Properties of Their Interface with Dopants”ACS Appl. Mater. Interfaces, 12, 51, 57578 (2020).

Acknowledgements:

ACKNOWLEDGMENTS
Funding by the Spanish Ministry of Science and Innovation (MCIN) and State Investigation Agency (AEI)
under Projects PID2022-136802NB-I00 (AEI/FEDER, UE), PID2019-110907GB-I00 and through the Severo Ochoa Programme for Centres of
Excellence in R&D (Grant CEX2023-001263-S) and UNFUTURE CEX2019-000917-S

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