Page 140 - Organic Electronics in Sensors and Biotechnology

CHAPTER 4

Integrated

Pyroelectric

Sensors

Barbara Stadlober, Helmut Schön,
Jonas Groten, Martin Zirkl, and Georg Jakopic
Institute of Nanostructured Materials and Photonics
Joanneum Research Forchungsgesellchaft
Weiz, Austria

4.1 Electrical Semiconductor and Dielectric Analysis

4.1.1 Impedance Spectroscopy (Basics, Impedance
Elements, Ideal and Nonideal MIS Structures)
This chapter deals with the characterization of the electronic proper-
ties of organic materials by impedance spectroscopy. The motivation
for this is novel organic devices, whose electronic properties are not
yet fully known, such as OFETs, OLEDs, and OPDs, which are
described in greater detail in other chapters. To understand an elec-
tronic device, it is essential to know its equivalent circuit (EC). If the EC
contains capacitive or inductive elements, its impedance will show
frequency dependence. Hence measuring the impedance spectrum (IS)
of an electronic device over a large frequency range enables determi-
nation of the elements of the underlying EC.
In practice, the determination of EC can be complicated by several
factors. First, the EC of the device under test (DUT) is often unknown. In
this case the problem is not only quantitative but also qualitative. This
requires an algorithm for the interpretation of the IS that cannot be given
for the general case. Second, the IS of an EC is not necessarily unique—
different ECs can have identical impedance spectra. Third, the DUT
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