Partial shading of CIGS modules can lead to permanent damage of the module in the shaded area. This is caused by harmful reverse bias voltages in the shaded area which lead to reverse bias induced defects, also known as wormlike defects. A lot is already known about the origin and propagation of wormlike defects. However, the fundamental question; why is CIGS so sensitive to reverse bias damage? has not yet been answered. In this study we show that CIGS semiconductor material in the presence of an electric field will spontaneously decompose.