Aryl-Perfluoroaryl Interaction in Two-Dimensional Organic–Inorganic Hybrid Perovskites Boosts Stability and Photovoltaic Efficiency

Two-dimensional (2D) organic–inorganic
hybrid perovskites
(OIHPs) have showed impressive stability, compared to their three-dimensional
(3D) counterparts. However, tuning the chemical structure of the organic
cations to simultaneously improve the device performance and stability
of 2D OIHP solar cells is rarely reported. Here, we demonstrate that
by introducing a classic noncovalent aryl-perfluoroaryl interaction,
2D OIHP solar cells with 1:1 mixed phenethylammonium (PEA) and perfluorophenethylammonium
(F5-PEA) can achieve an efficiency of >10% with much enhanced stability
using a simple deposition at low temperature without using any additives.
The competing effects of surface morphology and crystal orientation
with an increased amount of F5-PEA result in the highest efficiency
at a 1:1 ratio, while single-crystal studies reveal the expected aryl-perfluoroaryl
interaction, accounting for the highest device stability of 2D OIHP
solar cell at 1:1 ratio as well. This work provides an example where
tuning the interactions of organic cations via molecular engineering
can have a profound effect on device performance and stability of
2D OIHP solar cells.

二维（2D）有机-无机杂化钙钛矿（organic–inorganic hybrid perovskites，OIHPs）相较于三维（3D）同类材料，展现出更为优异的稳定性。然而，通过调控有机阳离子的化学结构，同时提升二维有机-无机杂化钙钛矿太阳能电池的器件性能与稳定性的相关研究鲜有报道。本研究证实，引入经典的非共价芳基-全氟芳基相互作用后，采用简便的低温沉积工艺且无需添加任何助剂，即可制备出1:1混合苯乙胺（phenethylammonium，PEA）与全氟苯乙胺（perfluorophenethylammonium，F5-PEA）的二维有机-无机杂化钙钛矿太阳能电池，其光电转换效率可达10%以上，且稳定性得到显著增强。随着F5-PEA占比提升，表面形貌与晶体取向的竞争效应使得1:1配比下器件效率达到峰值；而单晶研究验证了预期的芳基-全氟芳基相互作用，这同样解释了1:1配比下二维有机-无机杂化钙钛矿太阳能电池具备最优稳定性的原因。本研究提供了一个范例：通过分子工程调控有机阳离子间的相互作用，可对二维有机-无机杂化钙钛矿太阳能电池的器件性能与稳定性产生深远影响。