Efficient and Air‐Stable Aqueous‐Processed Organic Solar Cells and Transistors: Impact of Water Addition on Processability and Thin‐Film Morphologies of Electroactive Materials

Abstract

transistors (OFETs), organic light emitting diodes and polymer solar cells (PSCs), developing ecofriendly processing methods suitable for industrial fabrication has become an important topic of recent investigations. [1,2] To this end, a great deal of research efforts have been devoted to phasing out halogenated solvents such as chloroform and chlorobenzene, which have been prevalent for optimizing the fabrication of lab-scale OFET and PSC devices, because they are detrimental to both human health and the environment. In this context, a wide range of halogenfree solvents including toluene, xylenes, and trimethylbenzenes have been recently proposed as greener solvent alternatives and some notable progress has been made. [3][4][5][6][7][8][9][10][11] However, it remains in question whether those halogen-free solvents, which are often claimed to be "green solvents," are indeed practically applicable at an industrial-scale for sustainable manufacturing of organic electronics due to the serious health hazards and harmful environmental impacts that they can pose (e.g., median lethal dose LD 50 for chlorobenzene: 1110 mg kg −1 , toluene: 5580 mg kg −1 , water: >90 000 mg kg −1 , and De minimis % limit allowed to release for chlorobenzeneThe authors report the development of a desirable aqueous process for ecofriendly fabrication of efficient and stable organic field-effect transistors (eco-OFETs) and polymer solar cells (eco-PSCs). Intriguingly, the addition of a typical antisolvent, water, to ethanol is found to remarkably enhance the solubility of oligoethylene glycol (OEG) side chain-based electroactive materials (e.g., the highly crystalline conjugated polymer PPDT2FBT-A and the fullerene monoadduct PC 61 BO 12 ). A water-ethanol cosolvent with a 1:1 molar ratio provides an increased solubility of PPDT2FBT-A from 2.3 to 42.9 mg mL −1 and that of PC 61 BO 12 from 0.3 to 40.5 mg mL −1 . Owing to the improved processability, efficient eco-OFETs with a hole mobility of 2.0 × 10 −2 cm 2 V −1 s −1 and eco-PSCs with a power conversion efficiency of 2.05% are successfully fabricated. In addition, the eco-PSCs fabricated with water-ethanol processing are highly stable under ambient conditions, showing the great potential of this new process for industrial scale application. To better understand the underlying role of water addition, the influence of water addition on the thinfilm morphologies and the performance of the eco-OFETs and eco-PSCs are studied. Additionally, it is demonstrated that the application of the aqueous process can be extended to a variety of other OEG-based material systems.

Molecular Engineering and Morphology Control of Polythiophene:Nonfullerene Acceptor Blends for High‐Performance Solar Cells

“…Recent studies demonstrated that replacing alkyls with oligo(ethylene glycol) side chains is able to generate water or alcohol soluble conjugated polymers and acceptors. [184][185][186][187] In addition, scalable coating methods such as blade coating, [188][189][190][191][192] and slot-die coating [193][194][195][196][197] and roll-to-roll printing [198,199] should be more extensively explored. 6) Development of PT-based all-polymer solar cells: All-polymer solar cells exhibit unique advantages, such as excellent mechanical property, good morphological stability, and readily tunable solution viscosity.…”

Managing Local Order in Conjugated Polymer Blends via Polarity Contrast

“…[8][9][10] Originally, alkyl side chains were introduced to aid solubility and, generally, processability; 11 while more recently polar side chains, such as those based on oligo(ethylene oxide) groups, have attracted interest as they render the base material more compatible with socalled 'green' solvents. 12,13 Moreover, polymer semiconductors, substituted with polar side chains, are interesting for bioelectronic applications, for instance, where mixed electron/ion conduction is required (e.g., in electrochemical transistors used for biomimetic signal transduction, ion pumps, bioactive sensing elements), or where high biocompatibility is needed, including biointegrated electronics and wearable devices. [14][15][16][17][18][19] However, side chains can inhibit backbone packing and aggregation, and often introduce undesired torsional backbone disorder.…”

Crystal structure of 2-butyl-6-(ethylamino)-1H-benzo[de]isoquinoline-1,3(2H)-dione, C18H20N2O2

“…Recently, organic conjugated molecular materials have become a research hotspot in the field of photoelectric molecular materials because of their wide application in photoluminescence [3][4][5], photoelectric devices [6,7], field effect transistors [8,9] and functional complexes [10]. 1,8-Naphthalimide derivatives are important organic conjugated molecules which can be used as fluorophores in the design of fluorescent probe [11] and prodrug [12].…”