peri-Fused polyaromatic molecular contacts for perovskite solar cells.

Molecule-based selective contacts have become a crucial component to ensure high-efficiency inverted perovskite solar cells 1-5 . These molecules always consist of a conjugated core with heteroatom substitution to render the desirable carrier-transport capability 6-9 . So far, the design of successful conjugation cores has been limited to two N-substituted π-conjugated structures, carbazole and triphenylamine, with molecular optimization evolving around their derivatives 2,5,10-12 . However, further improvement of the device longevity has been hampered by the concomitant limitations of the molecular stability induced by such heteroatom-substituted structures 13,14 . A more robust molecular contact without sacrificing the electronic properties is in urgent demand, but remains a challenge. Here we report a peri-fused polyaromatic core structure without heteroatom substitution that yields superior carrier transport and selectivity over conventional heteroatom-substituted core structures. This core structure produced a relatively chemically inert and structurally rigid molecular contact, which considerably improved the performance of perovskite solar cells in terms of both efficiency and durability. The champion device showed an efficiency up to 26.1% with greatly improved longevity under different accelerated-ageing tests.