In recent years, flexible electronic technology has achieved remarkable progress and has become increasingly important to sectors such as consumer electronics, automotive, retail, and healthcare. It is a technology that allows us to build electronic circuits on a flexible substrate thus making them bendable and stretchable. As predicted by IDTechEx, the overall market for flexible and organic electronics will grow from $31.7 billion in 2018 to $77.3 billion in 2029. Field effect transistors are fundamental building blocks for electronic circuits and systems. At present, planar structure organic field effect transistors are widely used in organic and optoelectronics due to low cost, low weight, and easy fabrication, and are attractive for flexible electronic devices. However, advancing their commercial applications poses challenges in realizing fast operation speed, low operation voltage, large current density, miniaturization/integration, lack of standardization, and mechanical flexibility. An effective approach to solve these problems is the vertical organic field effect transistor (VOFET), a vertically stacked source/drain electrode structure, due to its inherent small channel length and unique working principles. Several researchers have reported device structure optimization for improved performance based on source electrode, gate electrode, and vertical channel transportation. High performance novel organic semiconductors and their operation mechanism need further studies to explore their potential.

Potential applications of VOFET range from active matrix displays, vertical OLETs, flexible electronics and logic circuits, organic memory elements, and vertical field effect phototransistors. For next generation applications, we need wireless connections with users and to realize such systems, a series of functions, including accurate and complex signal processing, power management, communication, and wireless interface for data output are required for different sensors. Additionally, during the last decade, the exponential growth of mobile devices and wireless services created a considerable demand for radio frequency-based technologies. Meanwhile, the lighting industry has also been revolutionized due to the popularization of LED light bulbs, which are more economical and efficient. In that context, visible light communication (VLC) is a disruptive technology based on LEDs that offers a free spectrum and high data rate, which can potentially serve as a complementary technology to the current radio frequency standards.

The aim of this Special Issue is to collate articles in this field of opto-electronics. Original research and review articles are welcome.

Potential topics include but are not limited to the following:

• Novel device structure optimization techniques and deep understanding of the fundamental mechanisms in VOFET
• Optical properties of VOFET light emitting materials
• Electrophoretic displays (EPD)
• VOFET based enzyme biosensors and wireless interfaces
• Accurate compact device models for efficient circuit and system design
• Development of EDA tools for simulation of heterogeneous and homogeneous circuits
• Organic Photovoltaics (OPV)
• Lightwave System Applications
• Optical Wireless Communication for 5G Technology
• Deep reinforcement learning (DRL)
• 5G NR (New Radio) massive MIMO (Multiple Input Multiple Output) technology