Precise Control of Interfacial Charge Transport for Building Functional Optoelectronic Devices

Abstract

studies have not only improved device performance, but have even built novel functions. At present, interface engineering has become a research hotspot and has great potential for further applications in diverse fields, ranging from integrated circuits and energy conversion to catalysis and chemical/biosensors. Scientists with various backgrounds have been devoting great efforts to this area, which has moved from the simple improvement of device performance to branch out in broad directions, indicating its interdisciplinarity.As shown in Figure 1c, an important interface for an FET is the semiconductor/ electrode interface, which typically determines the efficiency of charge carrier injection and extraction. In general, the charge injection of a metal/organic semiconductor (OSC) junction can be described in terms of thermal electron emission or tunneling mechanisms, depending on the concentration of defect states inside the bandgap (Figure 1c, left and middle). [1] By carefully selecting the self-assembled monolayer (SAM) or thin buffer interlayer to modify the metal electrode (Figure 1c, right), the interface charge injection barrier can be fine-tuned, thereby significantly reducing the contact resistance of the device. More interestingly, by using a stimuli-responsive conformational isomer as a functional layer to modify the electrode interface, functionalization of the electrodes can be achieved. This concept laid the foundation for the construction of functional devices such as optical/electrical switches, memory, and photodetectors.The semiconductor/dielectric interface is another important interface in FETs, that governs carrier transport (Figure 1d, left), because generation, transport, and regulation of charge carriers all occur in the first few layers (<10 nm) of semiconductors at the interface (Figure 1d, middle). In addition, the modification of the dielectric surface has been shown to help reduce the defects, improve the roughness, change the polarity, and modulate the surface hydrophilic/hydrophobic properties. These changes further affect the transport of carriers at the semiconductor/dielectric interface (Figure 1d, right) and have a significant impact on the morphology of the semiconductor layer. Furthermore, modification of the interface with SAMs or stimuli-responsive layers offers an important and general methodology to improve device performance and even integrate new molecular functionalities, such as photocontrollable memory, superconductivity, and charge-trap memory, into organic electrical circuits. Optoelectronic devices and interfaces therein have captured great attention in both scientific and industrial communities because of the wide variety of their unique properties. From a materials chemistry point of view, each layer and individual component of an optoelectronic device possesses the possibility of flexible chemical modification, making it feasible to dope, mix, and physically/chemically modify the interface. Exploiting the novel properties in optoelectronic devices with diverse la...

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