High‐Performance Organic Electrochemical Transistors and Neuromorphic Devices Comprising Naphthalenediimide‐Dialkoxybithiazole Copolymers Bearing Glycol Ether Pendant Groups

Abstract

Organic electrochemical transistors (OECTs) have emerged as building blocks for low power circuits, biosensors, and neuromorphic computing. While p-type polymer materials for OECTs are well developed, the choice of highperformance n-type polymers is limited, despite being essential for cation and metabolite biosensors, and crucial for constructing complementary circuits. N-type conjugated polymers that have efficient ion-to-electron transduction are highly desired for electrochemical applications. In this contribution, three non-fused, planar naphthalenediimide (NDI)-dialkoxybithiazole (2Tz) copolymers, which systematically increase the amount of polar tri(ethylene glycol) (TEG) side chains: PNDI2OD-2Tz (0 TEG), PNDIODTEG-2Tz (1 TEG), PNDI2TEG-2Tz (2 TEG), are reported. It is demonstrated that the OECT performance increases with the number of TEG side chains resulting from the progressively higher hydrophilicity and larger electron affinities. Benefiting from the high electron mobility, excellent ion conduction capability, efficient ion-to-electron transduction, and low-lying lowest unoccupied molecular orbital energy level, the 2 TEG polymer achieves close to 10 5 on-off ratio, fast switching, 1000 stable operation cycles in aqueous electrolyte, and has a long shelf life. Moreover, the higher number TEG chain substituted polymer exhibits good conductance state retention over two orders of magnitudes in electrochemical resistive random-access memory devices, highlighting its potential for neuromorphic computing.

Towards organic electronics that learn at the body-machine interface: A materials journey

“…Recently, naphthalenediimidebithiophene (NDI)-based polymers have demonstrated remarkable success in OECTs as well as neuromorphic devices, but further investigation on this class is warranted. [63,64] Similar to p-type counterparts, the design of n-type OECTs materials targets the placement and balancing of polar sidechains onto known good electron conductors. An exception can be made here for a highly rigid n-type conductor, poly(benzimidazobe nzophenanthroline) (BBL), which has recently demonstrated ground-breaking and unique performance in OECT devices.…”

n-Type Organic Electrochemical Transistors with High Transconductance and Stability

“…OECTs based on n-type conjugated polymers (electron conductors) have been introduced as a promising platform to monitor the integrity of lipid bilayers and ion channel activity, as they specifically respond to cation fluxes . They also serve as a platform for sensitive microscale sensors for metabolites when combined with catalytic enzymes and, when paired with p-type OECTs, can lead to low power and high gain complementary bioelectronic circuits, increasing the sophistication of current applications. − One of the major obstacles toward real-world applications is the poor performance and stability of n-type conjugated polymers with respect to their p-type counterparts . A main indicator of material performance as mixed electronic–ionic conductors is the figure of merit μ C *, where μ is the charge carrier mobility and C * is the volumetric capacitance.…”

“…μ C * for the currently top-performing n-type conjugated polymer is up to 41.3 F cm –1 V –1 s –1 ( f-BTI2g-TVTCN ) and 563 F cm –1 V –1 s –1 for pgBTTT , a p-type conjugated polymer . While n-type polymers were demonstrated to reach C * values higher than those of p-type analogs, , their poor electronic mobility, up to 10 –2 cm 2 V –1 s –1 , limits the overall device performance. , …”

Donor Engineering Tuning the Analog Switching Range and Operational Stability of Organic Synaptic Transistors for Neuromorphic Systems

“…[ 9–11 ] Organic semiconducting materials provide the perfect platform for three‐terminal synaptic devices with the merits of being facile solution processable, mechanical flexibility, large‐area printing and favorable biocompatibility. [ 12–15 ] In particular, organic conjugated polymer as core components of organic synaptic devices have been widely implemented. Several types of conjugated polymers have been developed, including poly(3,4‐ethylendioxythiophene) ( PEDOT) , [ 16 ] poly(3‐hexylthiophen‐2,5‐diyl ( P 3 HT ), [ 17 ] glycolated polythiophene ( P(g 4 2T‐T ), [ 18 ] etc., and their synaptic performance has been demonstrated to be comparable with biological synapses, thus highly promising in processing biological signals.…”