Enhancement in the photovoltaic performance of planar perovskite solar cells by perovskite cluster engineering using an interfacial energy modifier.

The grain size and quality of hybrid organic-inorganic perovskite (HOIP) films greatly affect the performance of perovskite solar cells (PSCs). However, dripping an anti-solvent during the spin coating process induces rapid nucleation and reduces the grain size. Here, a facile method is developed to engineer clusters in precursor solution and obtain high-quality perovskite films with an enlarged grain size. A cluster interfacial modifier, chlorobenzene (CB), is added to precursor solution. The modifier increases the interfacial energy between the precursor cluster and the solvent. The increased interfacial energy suppresses the nucleation and gives rise to HOIP films with large grains and high crystallinity. The efficiency of PSCs based on this method is greatly improved from 17.55% to 19.5%.

The Effect of Methylammonium Iodide on the Supersaturation and Interfacial Energy of the Crystallization of Methylammonium Lead Triiodide Single Crystals.

It is very important to study the crystallization of hybrid organic-inorganic perovskites because their thin films are usually prepared from solution. The investigation on the growth of perovskite films is however limited by their polycrystallinity. In this work, methylammonium lead triiodide single crystals grown from solutions with different methylammonium iodide (MAI):lead iodide (PbI2 ) ratios were investigated. We observed a V-shaped dependence of the crystallization onset temperature on the MAI:PbI2 ratio. This is attributed to the MAI effects on the supersaturation of precursors and the interfacial energy of the crystal growth. At low MAI:PbI2 ratio (<1.7), more MAI leads to the supersaturation of the precursors at lower temperature. At high MAI:PbI2 ratio, the crystal growing plans change from (100)-plane dominated to (001)-plane dominated. The latter have higher interfacial energy than the former, leading to a higher crystallization onset temperature.

Synthesis and characterization of mixed ligand chiral nanoclusters.

Chiral mixed ligand silver nanoclusters were synthesized in the presence of a chiral and an achiral ligand. While the chiral ligand led mostly to the formation of nanoparticles, the presence of the achiral ligand drastically increased the yield of nanoclusters with enhanced chiral properties.