Boron-doped zinc oxide thin films grown by metal organic chemical vapor deposition for bifacial a-Si:H/c-Si heterojunction solar cells

Abstract

Boron-doped zinc oxide (BZO) films were grown by metal organic chemical vapor deposition. The influence of B2H6 flow rate and substrate temperature on the microstructure, optical, and electrical properties of BZO films was investigated by X-ray diffraction spectrum, scanning electron microscope, optical transmittance spectrum, and Hall measurements. The BZO films with optical transmittance above 85% in the visible and infrared light range, resistivity of 0.9–1.0×10−3 Ωcm, mobility of 16.5–25.5cm2/Vs, and carrier concentration of 2.2–2.7×1020cm−3 were deposited under optimized conditions. The optimum BZO films were applied on the bifacial BZO/p-type a-Si:H/i-type a-Si:H/n-type c-Si/i-type a-Si:H/n+-type a-Si:H/BZO heterojunction solar cell as both front and back transparent electrodes. Meanwhile, the bifacial heterojunction solar cell with indium tin oxide (ITO) as both front and back transparent electrodes was fabricated. The efficiencies of 17.788% (open-circuit voltage: 0.628V, short-circuit current density: 41.756mA/cm2 and fill factor: 0.678) and 16.443% (open-circuit voltage: 0.590V, short-circuit current density: 36.515mA/cm2 and fill factor: 0.762) were obtained on the a-Si/c-Si heterojunction solar cell with BZO and ITO transparent electrodes, respectively.