Thousand-fold Conductivity Increase in 2D Perovskites by Polydiacetylene Incorporation and Doping.

Two-dimensional (2D) organic-inorganic perovskites have rapidly become an attractive alternative to traditional three-dimensional (3D) perovskite solar-cell absorbers owing to their improved stability and processability. Despite their advantages, the insulating nature of the organic cations and diminished light absorption limit their overall performance. Herein, it is demonstrated that the incorporation of conjugated diynes in hybrid 2D perovskites, and subsequent thermal treatment results in the formation of 2D perovskites that incorporate polydiacetylenes in their structure. Furthermore, it is shown that oxygen or iodine doping results in the formation of stable radicals within the material alongside a drastic shift of the band gap from 3.0 to 1.4 eV and in-plane conductivity improvements of up to three orders of magnitude, which lead to record conductivities for 2D halide perovskites (n=1).

Incorporation of Conjugated Diynes in Perovskites and their Post-Synthetic Modification.

Two-dimensional (2D) organic-inorganic hybrid perovskites have rapidly become an attractive alternative to three-dimensional (3D) perovskites as solar cell absorbers, owing to their improved stability, versatility, and ease of processing. Despite their advantages, the insulating nature of the organic cations makes these materials have lower absorbing and conducting properties, resulting in lower device efficiencies. A way to circumvent these issues is the integration of functional molecules that help mitigate these limitations. In this study, six new perovskites composed of three distinct diynes are synthesized, all of which can be thermally polymerized to form conjugated polymers within the perovskite layers. The incorporation of conjugated polymers results in drastic changes in these materials' optoelectronic properties and their overall stability. Furthermore, depending on the nature of the diyne and the inorganic layers, the materials show varying polymerization yields, optical bandgaps, and charge carrier densities. These results afford significant insight into the chemical nature of the polymerized species and thus highlight the versatility of this approach to post-synthetically generate conducting polymers within the layers of 2D perovskites, paving the way toward their use in optoelectronic devices.