FeCl3-functionalized graphene oxide/single-wall carbon nanotube/silicon heterojunction solar cells with an efficiency of 17.5%

Single-wall carbon nanotube/silicon (SWCNT/Si) heterojunction solar cells are no longer a laboratory curiosity, but the commercial manufacture of devices with a high and stable conversion efficiency remains a big challenge. Here we report the fabrication of a FeCl3-functionalized GO/SWCNT/Si heterojunction solar cell by using a simple drop-casting method. It was found that the GO layer not only serves as an antireflection layer, leading to reduced incident light loss and a similar to 20% increase in photocurrent, but also acts as a carrier transport bridge and physical barrier that traps more metal chloride. The FeCl3 acts as a solid-state redox functional material doping both the GO and the SWCNT film, resulting in a higher-conductivity composite film, which increases the work function and the charge carrier transport, contributing to a significant increase of the photovoltage and fill factor. As a result, the FeCl3-GO/SWCNT/Si heterojunction solar cell achieved a high conversion efficiency of 17.5% and good stability, where more than 90% of original efficiency was retained after exposure to air for 15 days.