Boosting Spiro‐OMeTAD Doping via Structurally Asymmetrical Nanohorns for High‐Performance Carbon‐Based Perovskite Solar Cells

Carbon nanohorns (CNH) to enhance the doping level of Spiro-OMeTAD is reported. The unique asymmetry and polar structure of CNH not only enable effective charge transfer between CNH and Spiro-OMeTAD, also exhibit confinement effect to trap Li⁺ ions and O₂, promoting the consecutive chemical doping processes.

Abstract

The doping level of 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (Spiro-OMeTAD), a commonly used hole transport layer in perovskite solar cells (PSCs), is crucial for its electrical conductivity and the final photovoltaic performance. The routine oxygen-oxidation doping strategy falls short in achieving high-level doping due to the sparsity and random distribution of dopants within the solid Spiro-OMeTAD film. Here the use of carbon nanohorns (CNH) as a promoter to significantly enhance the doping level of Spiro-OMeTAD is reported. The unique asymmetry and polar structure of CNH not only enable effective charge transfer between CNH and Spiro-OMeTAD, also exhibit confinement effect to trap Li⁺ ions and O₂, promoting the consecutive chemical doping processes. Corresponding carbon-based PSCs achieved a power conversion efficiency of 23.24% (22.51% certified), and demonstrated exceptional long-term durability, retaining 95.3% of the initial PCE (power conversion efficiency) after 1500 h of tracking at maximum power point (MPP) under 100 mW cm⁻² illumination.