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%.

Variable temperature and high-pressure crystal chemistry of perovskite formamidinium lead iodide: a single crystal X-ray diffraction and computational study.

We investigate the variable temperature (100-450 K) and high-pressure (p = ambient - 0.74 GPa) crystal chemistry of the black perovskite formamidinium lead iodide, [(NH2)2CH]PbI3, using single crystal X-ray diffraction. In both cases we find a phase transition to a tetragonal phase. Our experimental results are combined with first principles calculations, providing information about the electronic properties of [(NH2)2CH]PbI3 as well as the most probable orientation of the [(NH2)2CH]+ cations.