Metal phthalocyanines have gained considerable research attention as hole-transport materials (HTMs) in perovskite solar cells (PSCs) because of their superb stability. In this work, Ze Yu and coworkers reported the application of a copper naphthalocyanine derivative (namely tBu-CuNc) as a hole-transport material in PSCs. Compared to its phthalocyanine analogue, the π-conjugation extension of tBu-CuNc leads to not only an enhanced hole-carrier mobility associated with a stronger intermolecular π-π stacking, but also an elevated glass transition temperature of 252°C. The resultant PSCs employing tBu-CuNc afford an excellent power conversion efficiency of 24.03%, which is the highest value reported thus far for metal complex-based HTMs in PSCs. More importantly, the encapsulated tBu-CuNc-based devices also exhibit dramatically improved thermal stability than the devices using the state-of-the-art HTM Spiro-OMeTAD, with a T80 lifetime after more than 1,000 h under damp-heat stress (85°C/85% relative humidity) following the ISOS-D-3 protocol. This work opens up a new direction for developing efficient and stable HTMs in PSCs (see the article on pages 2701–2709).

Metal phthalocyanines have gained considerable research attention as hole-transport materials (HTMs) in perovskite solar cells (PSCs) because of their superb stability. In this work, Ze Yu and coworkers reported the application of a copper naphthalocyanine derivative (namely tBu-CuNc) as a hole-transport material in PSCs. Compared to its phthalocyanine analogue, the π-conjugation extension of tBu-CuNc leads to not only an enhanced hole-carrier mobility associated with a stronger intermolecular π-π stacking, but also an elevated glass transition temperature of 252°C. The resultant PSCs employing tBu-CuNc afford an excellent power conversion efficiency of 24.03%, which is the highest value reported thus far for metal complex-based HTMs in PSCs. More importantly, the encapsulated tBu-CuNc-based devices also exhibit dramatically improved thermal stability than the devices using the state-of-the-art HTM Spiro-OMeTAD, with a T80 lifetime after more than 1,000 h under damp-heat stress (85°C/85% relative humidity) following the ISOS-D-3 protocol. This work opens up a new direction for developing efficient and stable HTMs in PSCs (see the article on pages 2701–2709).