Direct Growth of Vertically Aligned Carbon Nanotubes onto Transparent Conductive Oxide Glass for Enhanced Charge Extraction in Perovskite Solar Cells

Vertically aligned carbon nanotubes (VACNTs) present an exciting avenue for nanoelectronics due to their pre-determined orientation and exceptional transport capabilities along the tube length, with the potential to employ in a variety of optoelectronic applications. However, growth of VACNTs using conventional chemical vapour deposition (CVD) methods requires elevated temperatures (>720°C) and therefore, the suitability of commonly used transparent conductive oxide (TCO) glasses, such as fluorine-tin oxide (FTO) and indium-tin oxide (ITO), as the substrates for nanotube growth are limited by their temperature-sensitive nature. Here, the successful growth of multi-walled VACNTs directly onto commonly used TCO glasses, FTO and ITO, using the photo-thermal chemical vapour deposition (PTCVD) growth method is reported. The benefit of reflection, within the infrared region, of the TCO substrate and the effect of surface roughness on the growth of VACNTs is investigated. The application of VACNTs on ITO in inverted planar perovskite solar cells is investigated, which show superior charge transfer, larger grain sizes in the perovskite film, and a champion device efficiency approaching 16%.