Extending the π-Conjugated System in Spiro-Type Hole Transport Material Enhances the Efficiency and Stability of Perovskite Solar Modules

Hole transport materials (HTMs) are a key component of perovskite solar cells (PSCs). The small molecular 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl)-amine-9,9'-spirobifluorene (spiro-OMeTAD, termed Spiro) is the most successful HTM used in PSCs, but its versatility is imperfect. To improve its performance, we developed a novel spiro-type HTM (termed DP) by substituting four anisole units on Spiro with 4-methoxybiphenyl moieties. By extending the p-conjugation of Spiro in this way, the HOMO level of the HTM matches well with the perovskite valence band, enhancing hole mobility and increasing the glass transition temperature. DP-based PSC achieves high power conversion efficiencies (PCEs) of 25.24 % for small-area (0.06 cm(2)) devices and 21.86 % for modules (designated area of 27.56 cm(2)), along with the certified efficiency of 21.78 % on a designated area of 27.86 cm(2). The encapsulated DP-based devices maintain 95.1 % of the initial performance under ISOS-L-1 conditions after 2560 hours and 87 % at the ISOS-L-3 conditions over 600 hours.

Automated summary

In this study, a novel spiro-type HTM named DP was developed by substituting four anisole units on Spiro with 4-methoxybiphenyl moieties, improving the performance of perovskite solar cells. The DP-based PSC achieved high power conversion efficiencies of 25.24% for small-area devices and 21.86% for modules, with a certified efficiency of 21.78% on a designated area. The encapsulated DP-based devices maintained 95.1% of the initial performance after 2560 hours under ISOS-L-1 conditions and 87% under ISOS-L-3 conditions over 600 hours.