Self-Heating, Bistability, and Thermal Switching in Organic Semiconductors

Kaschura

et al. 2017

Sci Rep

In spite of interesting features as flexibility, organic thin-film transistors have commercially lagged behind due to the low mobilities of organic semiconductors associated with hopping transport. Furthermore, organic transistors usually have much larger channel lengths than their inorganic counterparts since high-resolution structuring is not available in low-cost production schemes. Here, we present an organic permeable-base transistor (OPBT) which, despite extremely simple processing without any high-resolution structuring, achieve a performance beyond what has so far been possible using organic semiconductors. With current densities above 1 kA cm−2 and switching speeds towards 100 MHz, they open the field of organic power electronics. Finding the physical limits and an effective mobility of only 0.06 cm2 V−1 s−1, this OPBT device architecture has much more potential if new materials optimized for its geometry will be developed.

Section: Resultsmentioning

confidence: 98%

Organic Power Electronics: Transistor Operation in the kA/cm2 Regime

Klinger

Kaschura

et al. 2017

Sci Rep

“…According to Langevin recombination, the charge carrier mobilities of both charge carrier types mediate the possibility for free electrons and free holes to find each other. The temperature dependence can well be approximated by an Arrhenius law, especially for the temperature range investigated in this work . The reason is that charges in the GDOS have to be activated from the equilibrium energy level, where most charge carriers sit at low concentrations, to a transport energy level, where finally the charge transport takes place .…”

Section: Resultsmentioning

confidence: 87%

Investigating Free Charge‐Carrier Recombination in Organic LEDs Using Open‐Circuit Conditions

Advanced Optical Materials

Reineke

2019

Although organic light‐emitting diodes (LEDs) are widely used in commercial applications, a comprehensive knowledge about the occurring recombination pathways is still absent. Especially access to the bandgap is needed to figure out which path the charge carriers take, key to further understand and optimize the latest generations of thin film LED technology. Here, state‐of‐the‐art organic LEDs are treated like solar cells by measuring the open‐circuit voltage under UV illumination. A variation of the illumination intensity and temperature gives access to the effective bandgap, the ideality factor and the recombination strength. A differential evaluation approach is implemented, yielding the full temperature and intensity dependence of these parameters. A radiative and a non‐radiative recombination process are identified and used to reconstruct the current density dependence of the external quantum efficiency. All recombination events are related to an effective bandgap that suggests free charge recombination between the guest and the host material of the emission layer. This approach will thus help to identify and eliminate non‐radiative recombination losses in LEDs based on other type of molecules emitters and materials, such as perovskites or quantum dots, as well. Knowing the effective bandgap will also be essential to realize LEDs with the lowest possible driving voltages.

“…An isothermal measurement of the transistor can only be attained in a pulsed measurement mode preventing the heat up of the device. A more detailed view on the self‐heating also describing the dynamics of heating is given by Fischer et al…”

Section: Overview Over Device Principles and State‐of‐the‐artmentioning

confidence: 99%

A Review of Vertical Organic Transistors

Kleemann

Krechan

et al. 2020

Adv Funct Materials

125

110

Powerful electronic devices require performant short‐channel transistors. For organic electronics, though, promising low‐cost and flexible electronic circuits, high processing costs for short channel devices are not acceptable. In this regard, vertical organic transistors (VOTs) are an attractive alternative, and in fact, today they reach the highest transition frequency (40 MHz) and the highest footprint current density (>1 MA cm−2) among all organic transistors. Here, all VOT concepts are reviewed, while discussing device physics, integration approaches, and highlighting the recent developments. The upcoming challenges for the VOT technology are also presented with a guideline for further developments.