Organic Photovoltaic Pseudocapacitors for Neurostimulation

Abstract

Neural interfaces are the fundamental tools to understand the brain and cure many nervous-system diseases. For proper interfacing, seamless integration, efficient and safe digital-to-biological signal transduction, and long operational lifetime are required. Here, we devised a wireless optoelectronic pseudocapacitor converting the optical energy to safe capacitive currents by dissociating the photogenerated excitons in the photovoltaic unit and effectively routing the holes to the supercapacitor electrode and the pseudocapacitive electrode–electrolyte interfacial layer of PEDOT:PSS for reversible faradic reactions. The biointerface showed high peak capacitive currents of ∼3 mA·cm –2 with total charge injection of ∼1 μC·cm –2 at responsivity of 30 mA·W –1 , generating high photovoltages over 400 mV for the main eye photoreception colors of blue, green, and red. Moreover, modification of PEDOT:PSS controls the charging/discharging phases leading to rapid capacitive photoresponse of 50 μs and effective membrane depolarization at the single-cell level. The neural interface has a device lifetime of over 1.5 years in the aqueous environment and showed stability without significant performance decrease after sterilization steps. Our results demonstrate that adopting the pseudocapacitance phenomenon on organic photovoltaics paves an ultraefficient, safe, and robust way toward communicating with biological systems.

Nanoengineering InP Quantum Dot-Based Photoactive Biointerfaces for Optical Control of Neurons

“…Different than capacitive double layer charging mechanism, the charging/discharging dynamics of photoelectrochemical current generation mechanism is dependent on the rates of electron transfer at electrode–electrolyte interface and the arrival rate of reaction ions to the interface ( Merrill et al, 2005 ). Capacitive biointerfaces have fast charging dynamics with rise times on the order of tens or hundreds of microseconds ( Ciocca et al, 2020 ; Han et al, 2020 ), whereas the decay times might be in milliseconds range ( Jakešová et al, 2019 ). On the other hand, faradaic devices have typically longer rise/fall times due to the slower charging–discharging kinetics governed by electron transfer rate and availability of ions at the reaction site ( Merrill et al, 2005 ; Bahmani Jalali et al, 2018b , 2019a ).…”

Bulk-heterojunction photocapacitors with high open-circuit voltage for low light intensity photostimulation of neurons

“…Moreover, a detailed stability study of the organic semiconductor materials with thiophene molecules as the building block in biological medium is discussed by Han et al, in which the time-dependent cyclic stability by measuring the peak value of the transient photocurrent is presented. 38 The recorded peak photocurrent density only decreased by 9.2% after 60 days, relative to the first day, which corresponds to a device half-time of B1.8 years in an aqueous environment.…”

Comprehensive Understanding of Sodium‐Ion Capacitors: Definition, Mechanisms, Configurations, Materials, Key Technologies, and Future Developments

“…Pseudocapacitance can be regarded as a complementary mechanism of EDLC because it is not the mechanism of electrostatic adsorption, but has similar shapes of cyclic voltammetry (CV) curves and comparable tendency of galvanostatic charge and discharge (GCD) curves compared to EDLC. [ 85 ] On the other hand, pseudocapacitive materials in anodes are also the main interests in SICs devises. Nevertheless, with the fast growth of nanotechnology and nanoscience in anodes, nanomaterial anodes have played an important role in electrochemical energy devices over these years.…”