Organic photodetectors can achieve narrowband photodetection within a single optoelectronic device. This comprehensive review summarizes and compares the different approaches, introduces their application fields, and outlines current challenges.

The Organic Permeable Base Transistor (OPBT) is currently the fastest organic transistor with a transition frequency of 40 MHz. It relies on a thin aluminum base electrode to control the transistor current. This electrode is surrounded by a native oxide layer for passivation, currently created by oxidation in air. However, this process is not reliable and leads to large performance variations between samples, slow production and relatively high leakage currents. Here, we demonstrate for the first time that electrochemical anodization can be conveniently employed for the fabrication of high performance OPBTs with vastly reduced leakage currents and more controlled process parameters. Very large transmission factors of 99.9996% are achieved, while excellent on/off ratios of 5x10 5 and high oncurrents greater than 300 mA/cm² show that the C 60 semiconductor layer can withstand the electrochemical anodization. These results make anodization an intriguing option for innovative organic transistor design.Pre-peer reviewed version of communication published in Advanced Materials, March 2019 https://doi.

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Unfortunately, high-resolution patterning techniques operating in the nanometer regime are costly and currently incompatible with the promise of low-cost flexible electronics. Hence, new device concepts need to be conceived which allow for an ultra-short channel length in conjunction with low fabrication costs. In this regard, vertical organic transistors with a channel length of ≈100 nm have generated significant interest in recent years, [4][5][6][7][8][9][10] as the vertical dimensions of an organic transistor can be easily controlled over the nanometer regime. The organic permeable base transistor (OPBT) is a truly vertical device with a semiconductor thickness in the order of 100 nm. Due to the extraordinarily short channel and a reduced influence of the contact resistance, [11] the OPBT can drive very large current densities above 1 kA cm −2[12] and reaches record-high transition frequencies of 40 MHz, [3] making it the fastest organic transistor to date. The transistor consists of a vertical stack of three electrodes separated by organic semiconductor layers. The outer electrodes constitute emitter and collector, while the central electrode is the base. It has native nano-sized holes, making it permeable for electrons. Current leakage into the base is prevented by a native oxide film around the electrode. In the on-state, a charge-accumulation channel at the oxide interface is formed, ensuring efficient charge transport through the base, while in the off-state the base potential hinders the charge conduction through the pinholes. Figure 1 shows a cross-sectional transmission electron microscopy (TEM) image of an OPBT with C 60 semiconductor layers and the ultra-thin permeable base electrode of aluminum.These advances enable a broad range of possible applications for OPBTs, including display driver circuits where high currents and fast switching are needed, [13] and radio-frequency identification (RFID) systems with MHz operation. [14,15] Realworld applications, however, require a number of other properties like integrateablity, low power consumption, and stability. OPBTs operate on low voltages, generally enabling facile integration into electronic circuits. The static power consumption of OPBTs was recently dramatically reduced by the introduction of a controlled base oxidation technique. [16] Stability, though, has not yet been studied for OPBTs and there is little research regarding the behavior of short-channel vertical organic transistors under continued electrical stress.Vertical organic permeable base transistors (OPBT) can drive large current densities of kA cm −2 and achieve record-high transition frequencies of up to 40 MHz. They are therefore an interesting candidate for numerous applications, including the use in active-matrix organic light emitting display (AMOLED) backplanes. However, the transistor characteristics are required to be stable against electrical stress. Here, the threshold voltage shifts under current-and voltage-stress conditions over various temperatures and illumination condi...

Vertical organic transistors have emerged as a new device concept holding great promise to overcome the limitations of lateral organic transistors. In this regard, the organic permeable base transistor (OPBT), a special kind of vertical transistor, stands out due to excellent performance figures such as low‐voltage operation and high transition frequency measured in a pulse‐biasing mode. On the occasion of Prof. Karl Leo's 60th birthday, his contributions to the development of high‐performance OPBTs are honored and a perspective for the future of OPBT development is provided. The current state of the art of OPBTs is reviewed and the principles of the device operation are summarized. New insights into the formation of the permeable base layer, which is vital to the function of OPBTs, are discussed. Additionally, a full yield analysis on a batch of 144 equivalent OPBTs is reported and the device yield and temporal evolution of device parameters are statistically analyzed. This analysis proves a device yield of >90% for these short‐channel transistors, rendering the possibility for circuit integration. Finally, the scaling laws of OPBTs are derived and strategies for new materials and device layouts to push the performance to the gigahertz regime are concluded.

Organic permeable base transistors (OPBTs) are of great interest for flexible electronic circuits, as they offer very large on‐current density and a record‐high transition frequency. They rely on a vertical device architecture with current transport through native pinholes in a central base electrode. This study investigates the impact of pinhole density and pinhole diameter on the DC device performance in OPBTs based on experimental data and TCAD simulation results. A pinhole density of NPin = 54 µm−2 and pinhole diameters around LPin = 15 nm are found in the devices. Simulations show that a variation of pinhole diameter and density around these numbers has only a minor impact on the DC device characteristics. A variation of the pinhole diameter and density by up to 100% lead to a deviation of less than 4% in threshold voltage, on/off current ratio, and sub‐threshold slope. Hence, the fabrication of OPBTs with reliable device characteristics is possible regardless of statistical deviations in thin film formation.

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