Integration of p-type-doped carbon nanostructures as additives for boosting spiro-OMeTAD performance in perovskite solar cells

Abstract

The application of chemically modified carbon nanotubes (CNTs) and nanohorns (CNHs) for perovskite solar cells (PSCs) has been almost limited to their use as electrodes, underutilizing their potential as charge-selective transporting materials. In this work, a comprehensive study of the implementation of carbon nanomaterials (CNMs) as additives for spiro-OMeTAD is presented. A detailed chemical characterization of the hybrid carbon nanostructures is performed, including optoelectronic and thermal properties, showing the potential of the modified CNMs to be implemented in photovoltaic devices. The incorporation of CNMs into spiro-OMeTAD induces an energy shift of the spiro-OMeTAD energy levels, optimizing the energy band alignment with the perovskite when spiro-OMeTAD is combined with porphyrin-functionalized single-wall CNTs (SWCNTs). CNM-doped spiro-OMeTAD resulted in improved power conversion efficiencies (PCEs) in comparison to the reference devices, reaching a maximum PCE of 19.8% for zinc-metalated porphyrin (ZnP)-SWCNT hybrids. The PCE enhancement is primarily attributed to the improved morphology and contact interface of the perovskite/hole-transporting material (HTM) layer, as well as to the increased hole mobility. Furthermore, stability tests show an improvement in the stability under ambient storage for the cells incorporating porphyrin-functionalized SWCNTs compared to the reference device, which is ascribed to the higher hydrophobicity resulting from the presence of CNMs.