Role of Stabilizing Surfactants on Capacitance, Charge, and Ion Transport in Organic Nanoparticle-Based Electronic Devices

Abstract

Deposition of functionalized nanoparticles onto solid surfaces has created a new revolution in electronic devices. Surface adsorbates such as ionic surfactants or additives are often used to stabilize such nanoparticle suspensions; however, little is presently known about the influence of such surfactants and additives on specific electronic and chemical functionality of nanoparticulate electronic devices. This work combines experimental measurements and theoretical models to probe the role of an ionic surfactant in the fundamental physical chemistry and electronic charge carrier behavior of photodiode devices prepared using multicomponent organic electronic nanoparticles. A large capacitance was detected, which could be subsequently manipulated using the external stimuli of light, temperature, and electric fields. It was demonstrated that analyzing this capacitance through the framework of classical semiconductor analysis produced substantially misleading information on the electronic trap density of the nanoparticles. Electrochemical impedance measurements demonstrated that it is actually the stabilizing surfactant that creates capacitance through two distinct mechanisms, each of which influenced charge carrier behavior differently. The first mechanism involved a dipole layer created at the contact interfaces by mobile ions, a mechanism that could be replicated by addition of ions to solution-cast devices and was shown to be the major origin of restricted electronic performance. The second mechanism consisted of immobile ionic shells around individual nanoparticles and was shown to have a minor impact on device performance as it could be removed upon addition of electronic charge in the photodiodes through either illumination or external bias. The results confirmed that the surfactant ions do not create a significantly increased level of charge carrier traps as has been previously suspected, but rather, preventing the diffusion of mobile ions through the nanoparticulate film and their accumulation at contacts is critical to optimize the performance.

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

“…Furthermore, the nanoparticle approach also ensures that the thermodynamic control of the OSC film morphology is decoupled from the printing fabrication process, removing the need to consider solvent and thermal annealing treatments. Such nanoengineering approaches to building OSC devices thus enable the dual benefits of exquisite nanoscale film structure and low-cost, large-area printing of electronic devices to be simultaneously realized [86,87].…”

“…For example, the particle size can be customized between 20 and 200 nm to ensure that the crystalline domain feature size closely matches the exciton diffusion length in organic semiconductors [98,100]. The miniemulsion method does have the drawback of leaving residual insulating surfactant embedded in an electroactive device film [86,97]; however, recent progress has developed clever techniques to remove this surfactant using a temperatureinduced critical micelle concentration switching technique that reduces the temperature of the films, causing surfactants to aggregate and be washed out of the film [90]. Recently, the OSC nanoparticle approach was employed in a novel approach to indirect radiation detection, where the scintillator was embedded into a blended nanoparticle with a donor polymer material [7].…”

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

“…pore size) and molecular dynamics (e.g. flex-ibility) are provided by the conducting solid [10,11]. Polymer molecules can also be readily functionalised by various nanoengineering pathways in order to impart tunability to their optical, electronic, mechanical and physical properties through induced intermolecular interactions [55].…”

“…Organic electronic (OE) materials have attracted part-icular interest as ideal candidates for printed electronics applications. The suitability of OE materials for this purpose arises from the ability to easily modify their nanoscale che-mical, physical and electronic properties and thereby control their film-forming mechanisms and functionality in electronic devices [10]. Furthermore, it has been recently recognised that organic semiconductors have the unique advantage that the soft carbonbased materials are inherently compatible with the soft, elastic tissue in biological samples.…”

Effect of Different Ionic Surfactants on the Structural, Photophysical, and Morphological Properties of Water‐Based P3HT:PCBM Nanoparticle Dispersions and Films

“…[ 33–35 ] Also, different post‐process treatments have been proposed to minimize the effect of the surfactant. [ 36–38 ] Such studies usually focus on SPNs colloidal dispersion obtained using sodium dodecyl sulfate as the surfactant, in high concentration.…”