Bipolar device configurations

The single-layer devices, the bilayer devices (with and without the PAN-CSA network electrode), and the inverted devices discussed are unipolar devices operating under a single-bias condition. We now discuss two novel device configurations that can be operated in both forward and reverse dc biases as well as in ac modes the SCALE devices and color-variable bipolar/ac light-emitting devices. 

This chapter concentrates on organic bipolar transistors, including details about the basic operation principles, device configurations, and processing methods, and describing the various strategies that have been applied to achieve ambipolar transport. Touching upon small molecule-based FETs and the hybrid approach, the main focus will be on polymer-based bipolar transistors since they can provide one of the ultimate solutions for simple, low-cost fabrication of flexible bipolar FETs. 

Specific device configurations in which curtailment of misfit dislocation formation enhances performance are the heterojunction bipolar transistor and the modulation doped field effect transistor. In order to suppress misfit dislocation for-... 

Ma and coworkers [154] synthesized a bipolar luminescent PPV-based polymer 111, which contained both donor triarylamine and acceptor oxadiazole moieties in the backbone. A device fabricated with this polymer (ITO/PEDOT/111/CsF/Al) showed a maximum brightness of 3600 cd/m2 and a maximum luminescent efficiency of 0.65 cd/A (< el = 0.3%), about 15 times brighter and more efficient than the device of the same configuration with a nonoxadiazole polymer 112. 

The second alternative is an electronic load. This device is a circuit that has a controllable switch (typically a Darlington configured pair of bipolar transistors or a MOSFET) that can be modulated to conduct any level of current the user desires. An example of an electronic load circuit is presented in this chapter. The electronic load will be constructed piece by piece and tested separately. When all the pieces are constructed and simulated, the whole sum of the electronic load can be assembled and tested as a unit. 

Figure 3. Schematic of droplet configuration and PDLC device operation A) bipolar configuration, B) radial configuration.

When bipolar materials are available, i.e.- have the ability to carry both holes and electrons, the device structure can have a three layer configuration wherein the LE layer is sandwiched between the HTL and ETL, i.e.-... 

CMOS devices can develop a serious problem called latchup, in which junctions in different devices connect and form a forward-biased diode structure, leading to a catastrophic current which destroys the circuit. As illustrated in Fig. 14.5a, the latchnp is caused by the formation of a pnpn device between the terminal of VSS and VDD (see Chap. 9, Sect. 1.3). In a latchup condition, the pnpn device is biased snch that the collector current of the pnp bipolar transistor supplies a base current to the npn bipolar transistor in a positive feedback situation. The latchup can cause device function failure or even self-bumout. Figure 14.5b shows the bipolar components and resistive components of a latchup configuration. The conduction state of a pnp device requires Vq, and the conduction state... 

Electrodes are arranged in a bipolar configuration. These are low-voltage devices and breakdowns occur due to decomposition of solvent. The thermodynamic limit for an aqueous solution is around 1.2 V, while for a non-aqueous system it is 3.35 V... 

Suga T, Sugita S, Ohshiro H et al (2011) p- and n-type bipolar redox-active radical polymer toward totally organic polymer-based rechargeable devices with variable configuration. Adv Mater 23(6) 751-754... 

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