This review gives a comprehensive overview of recent progress made in mixed-halide hybrid perovskite materials, focusing in particular on the impact of halide substitution on optoelectronic properties and trends in carrier dynamics.

The self-assembly of colloidal nanocrystals into ordered architectures has attracted significant interest enabling innovative methods of manipulating physicochemical properties for targeted applications. This study reports the self-assembly of CsPbBr3 perovskite nanocrystals (NCs) in one-dimensional (1D) superlattice chains mediated by ligand–solvent interactions. CsPbBr3 NCs synthesized at ≥170 °C and purified in a nonpolar solvent, hexane, self-assembled into 1D chains, whereas those purified in polar solvents, including toluene and ethyl acetate, were disordered or formed short-range two-dimensional (2D) assemblies. The NCs assembled into 1D chains showed red shifts in both the absorbance and photoluminescence spectra relative to those of disordered NCs purified in a 50/50 hexane/ethyl acetate mixture. Microscopy and X-ray diffraction results confirmed the formation of polymeric nanostrands in hexane followed by organization of the NCs into 1D chains along the nanostrands. Our results suggest that excess aliphatic ligands remaining after purification of the NCs complex with ionic Cs+ and Br– species through a hydrophobic effect; further, the alkyl chains of these ligands interlace with each other through van der Waals forces. Collectively, these interactions give rise to the nanostrands and subsequent self-assembly of CsPbBr3 into 1D chains. In polar solvents, the minimization of repulsive forces between the solvent and the ligands drives proximal CsPbBr3 NCs together into short-range 2D assemblies or disordered clusters. Our solvent-assisted self-assembly approach provides a general strategy for designing 1D superlattice chains of nanocrystals of any geometry, dimension, and composition by simply tuning the ligand–solvent interactions.

In this work, we examine the impact of hybrid bimetallic Au/Ag core/shell nanostructures on the carrier dynamics of methylammonium lead tribromide (MAPbBr) mesoporous perovskite solar cells (PSCs). Plasmon-enhanced PSCs incorporated with Au/Ag nanostructures demonstrated improved light harvesting and increased power conversion efficiency by 26% relative to reference devices. Two complementary spectral techniques, transient absorption spectroscopy (TAS) and time-resolved photoluminescence (trPL), were employed to gain a mechanistic understanding of plasmonic enhancement processes. TAS revealed a decrease in the photobleach formation time, which suggests that the nanostructures improve hot carrier thermalization to an equilibrium distribution, relieving hot phonon bottleneck in MAPbBr perovskites. TAS also showed a decrease in carrier decay lifetimes, indicating that nanostructures enhance photoinduced carrier generation and promote efficient electron injection into TiO prior to bulk recombination. Furthermore, nanostructure-incorporated perovskite films demonstrated quenching in steady-state PL and decreases in trPL carrier lifetimes, providing further evidence of improved carrier injection in plasmon-enhanced mesoporous PSCs.