Synergistic Fluorine⋅⋅⋅Sulfur Intra- and Intermolecular Interactions on Dopant-free Hole Transport Material for Efficient and Stable Inverted Perovskite Solar Cells

Designing dopant-free small-molecular hole transport materials (HTMs) with a self-assembly behavior via noncovalent interactions has been considered one effective strategy to achieve high-performance inverted perovskite solar cells (PSCs). Here, we present two donor-π bridge-donor (D-π-D) HTMs, TPASF and TPAOF, containing 3,6-dimethoxythieno[3,2-b]thiophene as a core part with 3-fluoro-N,N-bis(4-(methylthio)phenyl)aniline and 3-fluoro-N,N-bis(4-methoxyphenyl)aniline as side groups. The synergistic F (fluorine)⋅⋅⋅S (sulfur) dipole-dipole intra- and intermolecular interactions in TPASF drive the self-assembly of this molecule into a supramolecular nanofibrillar network, leading to high hole mobility, superior interfacial properties, and providing a good growth template for the perovskite layer atop. The corresponding dopant-free TPASF-based inverted devices exhibit a promising power conversion efficiency of 21.01% with a long T80 lifetime of ~632 h under operational conditions. This work paves the way for the further development of new dopant-free self-assembled HTM designs for highly efficient and stable inverted PSCs.