Junyuan Ding

Abstract Flexible perovskite solar cells (pero‐SCs) are the best candidates to complement traditional silicon SCs in portable power applications. However, their mechanical, operational, and ambient stabilities are still unable to meet the practical demands because of the natural brittleness, residual tensile strain, and high defect density along the perovskite grain boundaries. To overcome these issues, a cross‐linkable monomer TA‐NI with dynamic covalent disulfide bonds, H‐bonds, and ammonium is carefully developed. The cross‐linking acts as “ligaments” attached on the perovskite grain boundaries. These “ligaments” consisting of elastomers and 1D perovskites can not only passivate the grain boundaries and enhance moisture resistance but also release the residual tensile strain and mechanical stress in 3D perovskite films. More importantly, the elastomer can repair bending‐induced mechanical cracks in the perovskite film because of dynamic self‐healing characteristics. The resultant flexible pero‐SCs exhibit promising improvements in efficiency, and record values (23.84% and 21.66%) are obtained for 0.062 and 1.004 cm 2 devices; the flexible devices also show overall improved stabilities with T 90 >20 000 bending cycles, operational stability with T 90 >1248 h, and ambient stability (relative humidity = 30%) with T 90 >3000 h. This strategy paves a new way for the industrial‐scale development of high‐performance flexible pero‐SCs.

Self-assembled monolayers (SAMs) based on carbazole with minimal parasitic absorption, such as the most widely used [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz), dominate the high-performance hole transport layer (HTL) for conventional organic solar cells (OSCs). However, the small dipole moment of the 2PACz molecules results in weak molecular dipole-dipole interactions, leading to disordered dipole orientation and restricting work function modulation, which causes serious interfacial energy loss. Here, we grafted thiophene groups at both ends of the carbazole in 2PACz to obtain an SAM material (Th-Cz), which formed a transient resonance structure during thermal annealing, resulting in a twice-enlarged dipole moment. This strengthened molecular dipole-dipole interactions, facilitating ordered arrangement and dipole orientation of the Th-Cz film, contributing to a higher work function, which enhanced hole extraction and suppressed energy losses at the SAM/active layer interface. Additionally, van der Waals interactions between Th-Cz and the donors enabled the donor crystallizing before the acceptor, and this phenomenon is different from the cocrystallization observed in 2PACz-based active layers. This manipulation of crystallization dynamics favors vertical phase separation with a donor-rich phase at the bottom of active layers, leading to balanced charge-carrier mobilities. The resultant OSCs based on PM6:Y6 and D18-Cl:N3:AT-β2O with Th-Cz as HTL achieved power conversion efficiencies (PCEs) of 19.34% and 20.91% (certified 20.67%), respectively, setting a record PCE for the PM6:Y6-based OSCs and achieving the highest certified PCE for single-junction OSCs to date. Notably, Th-Cz also demonstrated exceptional compatibility with flexible OSCs, delivering a record PCE of 19.63%.

Abstract High‐boiling‐point nonhalogenated solvents are superior solvents to produce large‐area organic solar cells (OSCs) in industry because of their wide processing window and low toxicity; while, these solvents with slow evaporation kinetics will lead excessive aggregation of state‐of‐the‐art small molecule acceptors (e.g. L8‐BO), delivering serious efficiency losses. Here, a heterogeneous nucleating agent strategy is developed by grafting oligo (ethylene glycol) side‐chains on L8‐BO (BTO‐BO). The formation energy of the obtained BTO‐BO; while, changing from liquid in a solvent to a crystalline phase, is lower than that of L8‐BO irrespective of the solvent type. When BTO‐BO is added as the third component into the active layer (e.g. PM6:L8‐BO), it easily assembles to form numerous seed crystals, which serve as nucleation sites to trigger heterogeneous nucleation and increase nucleation density of L8‐BO through strong hydrogen bonding interactions even in high‐boiling‐point nonhalogenated solvents. Therefore, it can effectively suppress excessive aggregation during growth, achieving ideal phase‐separation active layer with small domain sizes and high crystallinity. The resultant toluene‐processed OSCs exhibit a record power conversion efficiency (PCE) of 19.42% (certificated 19.12%) with excellent operational stability. The strategy also has superior advantages in large‐scale devices, showing a 15.03‐cm 2 module with a record PCE of 16.35% (certificated 15.97%).