Noncovalent Conformational Dopant-Free Hole Transport Materials with Multisite Passivation for Stable n-i-p Perovskite Solar Cells

High-performance, dopant-free hole transport materials (HTMs) play a crucial role in stabilized perovskite solar cells (PSCs). Skillfully using noncovalent bonding strategies to construct dopant-free HTM is both attractive and challenging. In this work, two dopant-free HTMs with multisite passivation are designed and synthesized. The core backbone is a heterocyclic lactam, and the intramolecular F···S noncovalent bonds are tuned by adjusting the position of F atoms. In TTPA-iF molecule, the noncovalent conformational lock minimizes the rotation of the core-terminal unit. This, in turn, reduces unfavorable reorganization energy and increases the molecular dipole moment. Compared to the amorphous films of TTPA-mF, the TTPA-iF films exhibit ordered molecular stacking and higher hole mobility. The rigid molecular conformation of TTPA-iF allows for more effective reduction of interfacial traps through multiple passivation sites and promotes carrier transport. As a result, PSCs with dopant-free TTPA-iF achieve a top efficiency of 24.28% and show significantly enhanced stability under various conditions in comparison to conventional doped HTMs. This research offers valuable insights and material options for the development of high-performance, dopant-free HTMs.