Beyond the Sum of Its Parts: Alkyl-Chain Engineering Unlocks Dopant-Free Pyrene-Based Antenna Molecules for Efficient...

The pursuit of high-performance, dopant-free hole-transporting materials (HTMs) is central to advancing the efficiency and stability of perovskite solar cells (PSCs). Herein, three pyrene-based HTMs (PyTPA-9C, PyTPA-10C, and PyTPA-13C) were synthesized by covalently linking two pyrene-triphenylamine precursor units, which display a pronounced antenna effect analogous to the precursor which is quantitatively defined by a positive correlation between the number of TPA antenna moieties and key photophysical parameters (such as molar absorption coefficient and fluorescence quantum yield). Critically, the odd-even effect of the alkyl spacer plays a significant role in modulating the molecular conformation and electronic structure. Moreover, PyTPA-10C, featuring an even-carbon decyl chain as a dopant-free HTMs in n-i-p structured PSCs, achieves a champion power conversion efficiency (PCE) of 25.47%, representing the highest reported values for n-i-p PSCs employing dopant-free, organic small-molecule HTMs. Comprehensive analysis reveals that PyTPA-10C enables superior hole extraction/transport, effectively suppresses charge recombination, and passivates interfacial defects. Consequently, unencapsulated devices retain over 90% of their initial PCE after 1000 h under continuous heating and illumination at 65°C and 50%-60% relative humidity. This study not only presents high-performing materials but also establishes a general molecular design strategy: the integration of an "antenna effect" with precise alkyl-chain engineering.