Reinforcing self-assembly of hole transport molecules for stable inverted perovskite solar cells.

Power conversion efficiencies (PCEs) of inverted perovskite solar cells (PSCs) have been improved by the use of a self-assembled monolayer (SAM) hole transport layer. Long-term stability of PSCs requires keeping the SAM compact under the perovskite layer during operation. We found that strong polar solvents in the perovskite precursor desorb the SAM if it is anchored on substrates by hydrogen-bonded, rather than covalently bonded, hydroxyl groups. We used atomic-layer deposition to create an indium tin oxide substrate with a fully covalent hydroxyl-covered surface for SAM anchoring, as well as a SAM with a trimethoxysilane group that exhibited strong tridentate anchoring to the substrate. The resulting PSCs achieved PCEs of 24.8 (certified 24.6) and 23.2% with aperture areas of 0.08 and 1.01 square centimeters, respectively. The devices retained 98.9 and 98.2% of the initial PCE after 1000 hours damp-heat test and operation in maximum power point tracking at 85°C for 1200 hours under standard illumination, respectively.

Effective Passivation with Self-Organized Molecules for Perovskite Photovoltaics.

Perovskite solar cells (PSCs) have achieved power conversion efficiencies (PCEs) exceeding 25% over the past decade and effective passivation for the interface with high trap density plays a significant role in this process. Here, two organic molecules are studied as passivators, and it is demonstrated that an advantageous molecular geometry and intermolecular ordering, aside from the functional moieties, are of great significance for effective and extensive passivation. Besides, the passivation molecules spontaneously form a uniform passivation network adjacent to the bottom surface of perovskite films during a top-down crystallization via liquid medium annealing, which greatly reduces defect-assisted recombination throughout the whole perovskite/SnO2 interface. The champion device yields an in-lab PCE of 25.05% (certified 24.39%). The investigation provides a more comprehensive understanding of passivation and a new avenue to achieve effective bottom-interface engineering for perovskite photovoltaics.