Boron-doped zinc oxide thin films for large-area solar cells grown by metal organic chemical vapor deposition

Boron-doped zinc oxide (ZnO:B) films were grown by metal organic chemical vapor deposition using diethylzinc (DEZn), and H2O as reactant gases and diborane (B2H6) as an n-type dopant gas. The structural, electrical and optical properties of ZnO films doped at different B2H6 flow rates were investigated. X-ray diffraction spectra and scanning electron microscopy images indicate that boron-doping plays an important role on the microstructure of ZnO films, which induced textured morphology. With optimized conditions, low sheet resistance (similar to 30 Omega/square), high transparency (> 85% in the visible light and infrared range) and high mobility (17.8 cm(2) V-1 s(-1)) were obtained for 700-nm ZnO:B films deposited on 20 cm x 20 cm glass substrates at the temperature of 443 K. After long-term exposure in air, the ZnO:B films also showed a better electrical stability than the un-doped samples. With the application of ZnO:B/Al back contacts, the short circuit current density was effectively enhanced by about 3 mA/cm(2) for a small area a-Si:H cell and a high efficiency of 9.1% was obtained for a large-area (20 cm x 20 cm) a-Si solar module. (c) 2006 Elsevier B.V. All rights reserved.