Mercury‐Mediated Organic Semiconductor Surface Doping Monitored by Electrolyte‐Gated Field‐Effect Transistors

Abstract

Surface doping allows tuning the electronic structure of semiconductors at near-surface regime and is normally accomplished through the deposition of an ultrathin layer on top or below the host material. Surface doping is particularly appealing in organic field-effect transistors (OFETs) where charge transport takes place at the first monolayers close to the dielectric surface. However, due to fabrication restrictions that OFET architecture imparts, this is extremely challenging. Here, it is demonstrated that mercury cations, Hg 2+ , can be exploited to control doping levels at the top surface of a thin film of a p-type organic semiconductor blended with polystyrene. Electrolyte-or water-gated field-effect transistors, which have its conductive channel at the top surface of the organic thin film, turn out to be a powerful tool for monitoring the process. A positive shift of the threshold voltage is observed in the devices upon Hg 2+ exposure. Remarkably, this interaction has been proved to be specific to Hg 2+ with respect to other divalent cations and sensitive down to nanomolar concentrations. Hence, this work also opens new perspectives for employing organic electronic transducers in portable sensors for the detection of an extremely harmful water pollutant without the need of using specific receptors.

Synergistic Effect of Solvent Vapor Annealing and Chemical Doping for Achieving High-Performance Organic Field-Effect Transistors with Ideal Electrical Characteristics

“…It should be noticed that UV–vis–NIR absorption, working in transmission configuration, probe both the doped surface and the deeper OSC layers, which could be much less affected by the doping, masking the effects of the iodine by averaging the signal over the entire film. 32 UV resonance Raman showed no changes or vibrational modes shift in the spectral pattern comparing the pristine C8-BTBT-C8 with the doped films in the different experimental conditions ( Figure S5 ), which confirms the absence of charge transfer complex or other chemical species formation.…”

Single‐Cell Membrane Potential Stimulation and Recording by an Electrolyte‐Gated Organic Field‐Effect Transistor

“…[23,24] The resulting films are highly crystalline and show high EGOFET performance and stability [23,24] and, thus, have already been applied for the development of sensors. [17,27,28] Figure 1c,d report the transfer and output characteristics of our device, highlighting that the field-effect current modulation is still present after cell seeding and culture.…”

Improving Nonvolatile Properties of Solid‐Electrolyte‐Based Artificial Synapses via Ion Dynamics Modulation in Organic Electrochemical Transistors

“…This is because after the first pulse stimulation was removed, the [TFSI] − was not completely dedoped, and the second stimulation further enhanced the doping level of [TFSI] − , thereby increasing the current of the device. This enhancement of the current gradually decreases with increasing time interval and can be fitted by Equation () [3, 23]. $$$\text{PPF}=1+{C}_{1}\text{exp}(-\unicode{x02206}t/{\tau }_{1})+{C}_{2}\text{exp}{\rm{}}(-\unicode{x02206}t/{\tau }_{2}).$$$where C 1 and C 2 are facilitation magnitudes; Δ t is the interval time; and τ 1 and τ 2 are the characteristic relaxation times for each phase.…”

“…Notably, the [TFSI] − OECT demonstrated superior LTP characteristics. Following the application of 300 consecutive pulses, the state retention of the different devices was compared and quantified using the memory level, which was defined as Memory level = 100% × (EPSC after − EPSC before )/(EPSC max − EPSC before ) (Figure 2G) [23]. The results revealed that the [TFSI] − OECT maintained 64% of the maximum current within 1000 s. In contrast, devices based on [BF 4 ] − and [OTf] − exhibited memory levels of only 31% and 28%, respectively, which are significantly lower than that of the [TFSI] − OECT.…”

“…Additionally, the fundamental performance characteristics (output curves) of the devices are shown in Supporting Information S1: Figure . To quantify the hysteresis phenomenon, the hysteresis window was defined as the voltage difference corresponding to half of the maximum I ds ( I on,max ) within a complete cycle of the linear transfer curve (Supporting Information S1: Figure ) [23]. The electrical performance of the devices was evaluated and compared using metrics such as maximum transconductance ( g m,max ), On/Off ratio, hysteresis window, and response time ( τ ) (Supporting Information S1: Figure ).…”