Degradation studies of transparent conducting oxide: a substrate for microcrystalline silicon thin film solar cells

Abstract

Aluminium doped ZnO films have been developed by RF-magnetron sputtering at 350 °C substrate temperature on glass substrate and commercially available SnO2-coated glass substrate. The developed ZnO and SnO2/ZnO films can be used as the substrates of microcrystalline silicon based solar cell. The electrical, optical properties and surface morphologies of ZnO film and SnO2/ZnO bi-layer films have been investigated and they are compared with the commercially available SnO2-coated glass substrate. The resistivities of ZnO and SnO2 films are comparable (∼10−4 Ω-cm). Surface morphologies of different transparent conducting oxide coated substrates before and after H-plasma exposure were studied by scanning electron microscopy. The optical transmission of ZnO, SnO2/ZnO and SnO2 films are comparable and varies from 85 to 90% in the visible region. The optical transmission reduces drastically to less than 20% in SnO2 films and for ZnO film it remains almost unchanged after H-plasma exposure. For SnO2/ZnO film transmission decreases slightly but remains considerably high (∼80%). The performance of microcrystalline silicon solar cells fabricated on different transparent conducting oxides as substrates (ZnO/glass, SnO2/glass and ZnO/SnO2/glass double layer) is investigated in detail.