T-shaped-N-doped polycyclic aromatic hydrocarbons: A new concept of dopant-free organic hole-transporting materials for perovskite solar cells

Although metal halide perovskites are positioned as the most powerful light-harvesting materials for sustainable energy conversion, there is a need for a thorough understanding of molecular design principles that would guide better engineering of organic hole-transporting materials (HTMs), which are vital for boosting the performance and stability of perovskite solar cells (PSCs). To address this formidable challenge, here, we developed a new design strategy based on the curved N-doped polycyclic aromatic hydrocarbon (N-PAHs) merged with T-shaped phenazines being decorated with (phenyl)- di-p-methoxyphenylamine (OMeTAD) – N-PAH23/24 and -3,6-ditertbutyl carbazole. (TBCz) – N-PAH25/26. As N-PAH23/24 exhibited satisfying thermal stability, the comparative studies performed with various experimental and simulation methods revealed a pronounced correlation between the depth of the central cyclazine core and the form of T-shape units. This proved to be a crucial factor in controlling their π-π intermolecular interaction as well as self-assembly behavior with the perovskite layer, leading to enhanced humidity resistance, operational stability, and a maximum power conversion efficiency (PCE) of 20.39% denoted for N-PAH23, which is superior to the benchmarked device with doped spiro-OMeTAD (19.23%). These studies resulted not only in optimized stability and device performance but also opened a conceptually new chemical space in photovoltaic technology.

National Science Centre: grant SONATA BIS 10, no. 2020/38/E/ST5/00267; National Science Centre, Poland, grant no. 2018/31/D/ST5/00426; scholarship awarded by the Polish Ministry of Education and Science to outstanding young scientists (2/DSP/2021); Foundation for Polish Science: START (093.2023).