Chapter 8 - Cu(In 1− xGa x)Se 2 and CuIn(Se 1− xS x) 2 Thin Film Solar Cells

Abstract

The chapter discusses the first hand fabrication and characterizations of CuInSe2 (CIS), CuGaSe2, and their alloy based cells. The work on CuInS2 and CuIn (Se1–xSx)2 alloy based cells are also discussed. The role of each layer in the thin film solar cell is thoroughly discussed. The band diagrams of the heterojunction solar cells with different buffer layers and working functions are presented by citing several examples. The high efficiency is observed in only vacuum processed cells those are not cost-effective to the mankind. In order to reduce cost, the low-cost techniques are essential to build thin film solar cells. Hence, the cells made by low-cost fabrication techniques are given preference to discuss even though their efficiencies are low. The fabrication of modules, the efficiency that decreases with increasing module size and solutions for the problems are described in this chapter. The quaternary Cu(In1–xGax)Se2 and CuIn(Se1–xSx)2 (x=0 to 1) compounds based thin film solar cells perish well with high efficiencies. The CuInSe2 is one of the potential components in the thin film solar cells, therefore, the growth process determines quality of CIS layers for which selenization process can be adopted to lead efficient cells. This process reduces voids and improves the good mechanical adhesion between CIS and Mo. The main stream of alloying Zn with CdS is to decrease lattice mismatch with CIS that contribute to reduce stacking faults and point defects at interface of CIS and CdS. The transparent conducting oxide (TCO) layer replaces Mo as a back contact in the CIGS thin film solar cells, which is beneficial for the tandem solar cells owing to its transparency, if it is used as a front side TCO in the solar cell.