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• The new materials of T-6TPA with high hole mobility of 2.06 × 10−3 cm2V−1s−1 was synthesized for dopant‐free HTL. • The infiltration strategies can further improve the interface hole extraction and transport between HTL and perovskite. • Anti-solvent drip strategy can construct a more effective charge transport channel in the perovskite. • The PCE of PSC with dopant-free T-6TPA HTL has increased from 18.5% to 20.3% with the assistance of antisolvent dripping. • The PSCs with T-6TPA dopant-free HTL presents good long-term stability in both humid air and high temperature of 60 °C. Perovskite solar cells (PSCs) with dopant‐free hole transporting layers (HTLs) deserved extensive research by merits of their outstanding hydrophobicity and stability. However, the low carrier mobility and poor interfacial hole extraction lead to the inferior power conversion efficiency (PCE) than that of conventional Li+ doped Spiro-OMeTAD. Here, a design of triphenylamine groups grafted triphenylene derivative (T-6TPA) as dopant-free HTLs has been presented. The larger π-conjugation in T-6TPA give rise to high hole mobility of 2.06 × 10−3 cm2V−1s−1. Moreover, the interfacial hole extraction of T-6TPA was significantly promoted when the molecules were infiltrated into perovskite before HTL deposition. The infiltration method of anti-solvent dripping (An) strategy increased PCE from 18.5% up to 20.3%, which is superior to another additive doping strategy (Ad-strategy, 19.3%). The effectiveness of An-strategy can be attributed to the construction of a coherent and homogeneous hole transport channel. The hydrophobicity and high glass transition temperature of T-6TPA also granted excellent moisture and thermal stabilities that the initial PCE could remain 80% for 60 days in air or 600 h at 60 °C. This work highlights the synergistical optimization by design of highly hole-mobile materials as well as the interfacial network construction for charge transport. [ABSTRACT FROM AUTHOR]

[Display omitted] • Lewis base groups are introduced into HTMs to restrict ion migration of Li+. • Phen-TPA effectively restricts ion migration of Li+ by strong coordination effect. • PSC based on Phen-TPA achieves a PCE of 20.02% with negligible hysteresis effect. • PSC based on Phen-TPA exhibits preferable humid and thermal stability. • The performance of PSCs is promoted with enhanced coordination ability of HTMs. Li-TFSI as an indispensable dopant for hole transporting materials (HTMs) suffers from inherent hydrophilicity and ion migration, which seriously damages the stability of perovskite solar cells (PSCs). Herein, a facile design strategy is proposed to restrict ion migration of Li+ by introducing different Lewis base groups (pyridine, 1,10-phenanthroline and pyrazine) into HTMs. Owing to the coordination effect of Lewis base groups to Li+, the doped HTMs (Pyrd-TPA, Phen-TPA and Pyra-TPA) exhibit significantly enhanced conjugation and hole mobility. Particularly, theoretical calculation and Fourier-transform infrared spectroscopy (FTIR) results demonstrate that Phen-TPA forms the strongest coordination with Li+ due to the most negative electrostatic potential region existing around 1,10-phenanthroline group. The generated Li+-coordinated Phen-TPA contributes to preferable energy levels, morphology uniformity and hydrophobicity. Element mapping analysis shows that Li-ion migration in doped Phen-TPA is restricted effectively. In addition, Phen-TPA can also passivate the perovskite surface defects dramatically, which facilitates more efficient charge transfer to hole transporting layer. Consequently, PSCs based on Phen-TPA achieve promising power conversion efficiency (PCE) of 20.02% with negligible hysteresis effect. More importantly, it maintains over 88% of the initial PCE after 1056 h storage in ambient condition of 40–60% RH and about 81% of the original efficiency after 264 h storage at 60–70 °C. This work systematically revealed the relation between coordination ability of HTMs and the performance of PSCs for the first time, which provides new design strategies to develop efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new strategy of developing high-performance dopant-free HTMs for PSCs is presented. • Two novel HTMs with intramolecular π-π interactions were developed for PSCs. • Crystal structures offer information on molecular configuration and interactions. • PSCs based on BFM-C6 showed a PCE of 19.06% with enhanced long-term stability. The development of hole-transporting materials (HTMs), especially dopant-free ones, is of great significance for simultaneously improving the efficiency and stability of perovskite solar cells (PSCs). Herein, two molecularly engineered HTMs (BFM-C1 and BFM-C6) featuring intramolecular π-π interactions are designed based on the well-known spiro-OMeTAD and synthesized via simple synthetic routes. Unlike the spiro-OMeTAD with orthogonal conformation, both BFM-C1 and BFM-C6 are revealed to adopt a "face-to-face" stacking orientation with evident intramolecular π-π interactions, and display about five times higher hole mobilities (≈ 10-4 cm2V-1s−1) than pristine spiro-OMeTAD. Moreover, both the HTMs exhibit high hole extraction capacity likely owing to good electronic contact with the perovskite. Notably, the incorporated long alkyl chains endow BFM-C6 with better film morphology and superior hydrophobicity, as compared with BFM-C1 , thereby resulting in enhanced charge extraction at the perovskite/HTM interface as well as the moisture stability of the perovskite underneath. Consequently, the PSCs employing BFM-C6 as HTM without dopants achieve a power conversion efficiency of 19.06%, along with preferable durability. Furthermore, BFM-C6 -based PSCs also exhibit improved thermal stability as compared to the devices based on doped spiro-OMeTAD. This work not only enriches the variety of dopant-free HTMs for PSCs, but also provide a new strategy for developing high-performance dopant-free HTMs. [ABSTRACT FROM AUTHOR]