Manipulating nanoscale structure to control functionality in printed organic photovoltaic, transistor and bioelectronic devices

Abstract

Printed electronics is simultaneously one of the most intensely studied emerging research areas in science and technology and one of the fastest growing commercial markets in the world today. For the past decade the potential for organic electronic (OE) materials to revolutionize this printed electronics space has been widely promoted. Such conviction in the potential of these carbonbased semiconducting materials arises from their ability to be dissolved in solution, and thus the exciting possibility of simply printing a range of multifunctional devices onto flexible substrates at high speeds for very low cost using standard roll-to-roll printing techniques. However, the transition from promising laboratory innovations to large scale prototypes requires precise control of nanoscale material and device structure across large areas during printing fabrication. Maintaining this nanoscale material control during printing presents a significant new challenge that demands the coupling of OE materials and devices with clever nanoscience fabrication approaches that are adapted to the limited thermodynamic levers available. In this review we present an update on the strategies and capabilities that are required in order to manipulate the nanoscale structure of large area printed organic photovoltaic (OPV), transistor and bioelectronics devices in order to control their device functionality. This discussion covers a range of efforts to manipulate the electroactive ink materials and their nanostructured assembly into devices, and also device processing strategies to tune the nanoscale material properties and assembly routes through printing fabrication. The review finishes by highlighting progress in printed OE devices that provide a feedback loop between laboratory nanoscience innovations and their feasibility in adapting to large scale printing fabrication. The ability to control material properties on the nanoscale whilst simultaneously printing functional devices on the square metre scale is prompting innovative developments in the targeted nanoscience required for OPV, transistor and biofunctional devices.

Printable Organic Semiconductors for Radiation Detection: From Fundamentals to Fabrication and Functionality

“…An increase in the degree of crystallinity of an OSC material is a frequently applied approach to improve carrier mobility [62]. When coating OSCs from ink solutions, rapid solvent evaporation prevents the spontaneous molecular ordering toward an equilibrium morphology, instead confining molecules in kinetically trapped states [63]. To counter this, several researchers have employed a strategy of slowing the OSC crystal growth down by precipitating OSC materials from solutions with high solubility into an orthogonal solvent.…”

“…Consequently, the structure-function relationships that have been so carefully elucidated on the laboratory scale over decades for many of the solar cell, transistor, and sensor devices that will be described in the following section do not translate directly to the larger scale. This discrepancy explains the significant gap between the high performance of small-scale devices and the lack of largerscale examples [63]. To bridge this "lab to fab" gap, a systematic pathway is used to transition from small-scale to roll-to-roll production environments in stages.…”

“…However, their generally low carrier mobility values (10 −3 -10 −5 cm 2 V −1 s −1 ) and poor radiation hardness present challenges for the assembly of practical radiation detectors [165]. To circumvent some of these limitations, the nanostructure of the OSC polymers can be manipulated as discussed previously [63]. However, the materials still face radiation hardness limitations and have historically been examined as disposable devices due to limited their shelf-life under irradiation from high-energy particles [1].…”

Flexible Polymer X-ray Detectors with Non-fullerene Acceptors for Enhanced Stability: Toward Printable Tissue Equivalent Devices for Medical Applications

“…From a fabrication perspective, the solubility of organic semiconductors allows for materials to be blended together into functional inks with control over the density and equivalent atomic number to tune the tissue equivalency match. Furthermore, these inks can be printed over large areas onto a variety of substrates at low cost, ,, including mechanically flexible substrates. , Organic photodetectors (OPDs) fabricated on flexible poly­(ethylene terephthalate) (PET) substrates have been previously reported, , demonstrating a mechanically flexible and optically transparent substrate for radiation detection. However, the plastic substrates commonly used for printed electronics [PET and poly­(ethylene naphthalate) (PEN)] have been reported to show fluorescence under high intensity X-ray radiation, such as commonly encountered in medical applications .…”

Controlling Nanostructure in Inkjet Printed Organic Transistors for Pressure Sensing Applications

“…The emergence of functional electronic devices created by low-cost printing techniques has created substantial interest in organic semiconductors as a particularly attractive class of materials for printed electronics [ 1 , 2 , 3 , 4 ]. The interest in organic semiconductors arises from two key features of these materials.…”