This paper reviews the three main thin film solar cell technologies: amorphous silicon (α-Si), copper indium gallium selenide (CIGS), and cadmium telluride (CdTe). The evolution of these three technologies is discussed in comparison to commercial applications, reliability, and market share. While the α-Si cell is almost extinct in terrestrial applications, CIGS and CdTe are comparable to multicrystalline solar cells, which have greater than 55% market share. Therefore, CIGS and CdTe thin film technologies are expected to compete with the crystalline solar cell technology. However, the longevity of thin film solar cells remains a problem that begs an answer before it can be explored on building integrated photovoltaic systems.