Lead-free low-dimensional tin halide perovskites with functional organic spacers: breaking the charge-transport bottleneck

Low-dimensional organic-inorganic halide perovskites (OIHPs) have received intense interest largely due to their remarkable stability compared to their 3D counterparts for potential optoelectronic and photovoltaic (PV) applications. However, 2D OIHPs encounter a 'bottleneck' of ultra-low conductivity between the inorganic sheets, owing to the intrinsic quantum and dielectric confinements, which usually results in unsatisfactory device performance. Herein, we predict and design a new family of 2D OIHPs to break the charge-transport 'bottleneck'. The newly designed 2D OIHPs consist of π-conjugated organic species as the spacers. As such, we find that the electronic structures exhibit type-II band alignment (staggered bandgap). Such a band-structure feature by design, if confirmed in the laboratory, re-enforces a materials design strategy for enhancing optoelectronic or PV device performance with 2D OIHPs.