This manuscript concerned with the interaction of light with TCO matter and some of its applications. The efficient conversion of an electrical signal to an optical signal and vice versa, is now of utmost importance. Similarly, rapid progress in semiconductor materials growth technology and the emergence of novel techniques in device fabrication has led to a continual improvement in the performance of optoelectronic devices. The rise in cost that is associated with this progress has incited condensed investigations in the fabrication of inexpensive technologies, which are becoming more and more likely. One of the import components of any high frequency optical system is a large bandwidth, low noise photoreceivers which may be realized using high speed transistors to act as preamplifiers. A wide range of materials and devices, including semi-transparent metal/semiconductor Schottky photodiodes and P-I-N diodes with heterojunction bipolar transistors have been used for this purpose.