Dion-Jacobson (DJ) phase 2D layered perovskites are developed by removing the van der Waals gap between organic layers and inorganic slabs in Ruddlesden-Popper (RP) phase counterparts. The hydrogen bonding formed at both sides of diammonium cations with perovskite layers in the DJ phase 2D perovskite endows it with extremely high structural stability, compared with that at only one side in the RP phase one. The devices exhibit a PCE of 13.3% with unprecedented stability, even when subjected to very harsh testing conditions.

Inspired by the structural feature of the classical hole-transport material (HTM), Spiro-OMeTAD, many analogues based on a highly symmetrical spiro-core were reported for perovskite solar cells (PSCs). However, these HTMs were prone to crystallize because of the high molecular symmetry, forming non-uniform films, unfavorable for the device stability and large-area processing. By lowering the symmetry of spiro-core, we report herein a novel spirobisindane-based HTM, Spiro-I, which could form amorphous films with high uniformity and morphological stability. Compared to the Spiro-OMeTAD-based PSCs, those containing Spiro-I exhibit similar efficiencies for small area but higher ones for large area (1 cm ), and especially much higher air stability (retaining 80 % of initial PCE after 2400 h storage without encapsulation). Moreover, the Spiro-I can be synthesized from a cheap starting material bisphenol A and used with a small amount for the device fabrication.

No abstract

No abstract

Methoxydiphenylamine-substituted carbazole (MODPACz) is widely used to construct hole-transporting materials (HTMs) for perovskite solar cells (PSCs), whose performances rely highly on the linking way of the MODPACz units and the simplicity of the π-bridge. In this paper, we report a new HTM, pPh-2MODPACz, using one of the simplest πbridges p-phenylene to link the MODPACz units. The structural feature endows pPh-2MODPACz with high hole mobility and conductivity, efficient hole extraction ability, and good film-forming property. MAPbI 3 -based PSCs using doped and undoped pPh-2MODPACz as the HTM offer efficiencies of ∼20% and 16.07%, respectively; both are better than those of the devices with spiro-OMeTAD as the HTM. The device stability of pPh-2MODPACz-based PSCs is also greatly enhanced. This work demonstrates that the simplest p-phenylene bridge for linking MODPACz can derive a promising HTM with a high device performance, providing a distinctive pathway to develop new HTMs.

No abstract

Various substituents have been incorporated into nonfullerene acceptors (NFAs) to modulate absorption scopes and energy levels for boosting efficiencies of organic solar cells (OSCs). The manipulation of the NFAs' molecular order and crystallinity via those substitutions is equally crucial to OSC performances, which yet remains interesting and challenging. The hydroxyl group, which can potentially form strong intermolecular hydrogen bonds (H‐bonds) for improving molecular arrangements, has, however, never been considered. Herein, two hydroxyl‐functionalized NFAs, IT‐OH with one hydroxyl and IT‐DOH with two hydroxyls, are synthesized to tune the molecular packing and crystallinity. The ordered molecular arrangement and higher crystallinity are observed for the IT‐OH and IT‐DOH than the parent ITIC. This is assigned to the formation of intermolecular H‐bonds induced by the hydroxyls, which elongates molecular conjugated planes leading to long‐range‐ordered structures via π–π stacking. By the appropriate crystallinity and miscibility with donor polymer, an IT‐DOH‐based nonannealed OSC affords an efficiency of 12.5% with good device stability. This work provides a promising strategy to tune the molecular packing and crystallinity to design NFAs by introducing hydroxyl groups.

No abstract