4
1 Introduction: Functions and Performances Governed by the Work Function
Transistor
CMOS
Solar
cell
BaƩery
Fuel
cell
LED
OLED
Electron
transfer
Sensor
Fig. 1.4 Applications related to electron transfer phenomena. See text for explanation
(chemical energy), the work function is a key to extracting electricity from the energy.
Another field related to energy conversion is sensors, where the amount of energy to
be converted is small. Again, the energy conversion efficiency is related to the work
function, where the efficiency determines the sensitivity.
1.2 Contents of the Following Chapters
As briefly overviewed in the above section, the work function plays an important role
in a very wide range of scientific, technological, and industrial fields. In the following
chapters, we discuss the physical origin of the work function, how the work function
can be controlled on the basis of physics, and how to design interfaces. In this section,
a guide to the following chapters is given.
In Chap. 2, the definition and the origin of the work function are given, and factors
that determine the value of the work function are explained. The most important point
is that the work function is defined for the surface of a material as well as for bulk
materials. In Chap. 3, strategies for tuning the work function are demonstrated on the
basis of the discussion in Chap. 2. Examples of work function modifications using