Vedran Derek1 Marie Jakesova1 Tobias Cramer2 Marek Havlicek3 David Rand4 Yael Hanein4 Daniel Simon1 Magnus Berggren1 Fredrik Elinder5 Eric Glowacki1

1, Laboratory of Organic Electronics, Department of Science and Technology, Linkoping University, Norrkoping, , Sweden
2, Department of Physics and Astronomy, Università di Bologna, Bologna, , Italy
3, Department of Nanometrology and Technical Length, Czech Metrology Institute, Brno, , Czechia
4, School of Electrical Engineering, Tel Aviv University, Ramat-Aviv, Tel-Aviv, , Israel
5, Department of Clinical and Experimental Medicine, Linkoping University, Linkoping, , Sweden

We have recently developed the organic electrolytic photocapacitor (OEPC), a nanoscale optoelectronic device for eliciting action potentials in neurons. Herein, we cover in detail the physical mechanisms behind the charge generation and dynamics of charging and capacitive coupling in these devices using optoelectronic/electrochemical measurements combined with simulation and modeling. Electrochemical impedance measurements allow corroboration of these models, and reveal the nature of photocapacitive and photofaradaic effects in the devices. Using scanning probe microscopy techniques, we have evaluated the mechanical properties of the nanocrystalline films, finding relatively low Young’s moduli in the range of 500 MPa. In order to take a reductive approach compared with previous measurements of neurons and electrogenic tissues, we have validated the performance of OEPCs using nonexcitable cells, xenopus laevis oocytes. We find rapid membrane potential changes in the range of tens to hundreds of millivolts are induced by OEPC devices, showing extremely effective capacitve coupling and explaining previous findings of action potential generation. The overall result of our work is a fuller physical and mechanistic understanding of this novel device platform, and a roadmap for guiding future development.