Improve the Stability of Hybrid Halide Perovskite via Atomic Layer Deposition on Activated Phenyl-C61 Butyric Acid Methyl Ester.

Atomic layer deposition (ALD) of oxide film on [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) shows a great promise to dramatically improve the ambient stability of hybrid halide perovskite. The nucleation of an ALD oxide on PCBM is critical to reliably apply this strategy. In this paper, we present the first study of the nucleation behavior of ALD oxides, including Al2O3 and ZnO, on PCBM. We find that PCBM film acts a gas diffusion barrier blocking the ALD reactants (diethyl zinc) from etching the underlying CH3NH3PbI3. However, ZnO is not able to nucleate on PCBM. We further identify that trimethyl aluminum, a strongly Lewis acid, reacts readily with C═O on PCBM to generate a seeding layer for nucleating ZnO ALD. This new chemical route is highly reliable and can be used to synthesize ALD ZnO coatings over PCBM. The synthesized PCBM/Al2O3-ZnO dramatically improves the stability of CH3NH3PbI3 against the ambience and even against liquid water. The result signifies the importance of understanding of nucleation of ALD in enabling reliable barrier coatings for hybrid halide perovskites.