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

Abstract

Boron-doped zinc oxide (ZnO:B) films were grown by metal organic chemical vapor deposition using diethylzinc (DEZn), and H 2O as reactant gases and diborane (B 2H 6) as an n-type dopant gas. The structural, electrical and optical properties of ZnO films doped at different B 2H 6 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 (∼ 30 Ω/□), 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 × 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 × 20 cm) a-Si solar module.