Intermolecular π-π Conjugation Self-Assembly to Stabilize Surface Passivation of Highly Efficient Perovskite Solar Cells.

Li, Hongshi; Shi, Jiangjian; Deng, Jun; Chen, Zijing; Li, Yiming; Zhao, Wenyan; Wu, Jionghua; Wu, Huijue et al. · Adv Mater · 2020

basic_science · Level V

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Abstract

Surface passivation is an effective approach to eliminate defects and thus to achieve efficient perovskite solar cells, while the stability of the passivation effect is a new concern for device stability engineering. Herein, tribenzylphosphine oxide (TBPO) is introduced to stably passivate the perovskite surface. A high efficiency exceeding 22%, with steady-state efficiency of 21.6%, is achieved, which is among the highest performances for TiO<sub>2</sub> planar cells, and the hysteresis is significantly suppressed. Further density functional theory (DFT) calculation reveals that the surface molecule superstructure induced by TBPO intermolecular π-π conjugation, such as the periodic interconnected structure, results in a high stability of TBPO-perovskite coordination and passivation. The passivated cell exhibits significantly improved stability, with sustaining 92% of initial efficiency after 250 h maximum-power-point tracking. Therefore, the construction of a stabilized surface passivation in this work represents great progress in the stability engineering of perovskite solar cells.