The role of cesium in retarding perovskite crystallization for enhanced grain size and ultra-smooth surface giving an efficiency of ∼19%.

The role of graphene nanoplatelets (GnPs) in a CH 3 NH 3 PbI 3 -based perovskite device was investigated for the first time. The activated GnPs were introduced in the mesoporous TiO 2 by a simple solution process. The morphology and optoelectronic properties of the anatase TiO 2 layer was modified with the presence of GnPs. The introduction of GnPs modified the bad-gap properties and passivated the oxygen-based surficial defects, leading to reduced interfacial recombination and efficient charge-carrier transportation. An overall increment in the efficiency of 25% was observed from ∼15 to 19% with the introduction of 2.0 wt % of GnPs. In addition, the device exhibits negligible hysteresis and enhanced stability. This work opens up new applications of GnPs to be utilized in solar cells and can be extended to other types of photovoltaic devices.

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