We show the influence of species present in precursor solution during formation of lead halide perovskite materials on the structural defects of the films. The coordination of lead by competing solvent molecules and iodide ions dictate the type of complexes present in the films. Depending on the processing conditions all PbIS5 (+) , PbI2 S4, PbI3 S3 (-) , PbI4 S2 (2-) , PbI5 S2 (3-) , PbI6 (4-) and 1D (Pb2 I4 )n chains are observed by absorption measurements. Different parameters are studied such as polarity of the solvent, concentration of iodide ions, concentration of solvent molecules and temperature. It is concluded that strongly coordinating solvents will preferentially form species with a low number of iodide ions and less coordinative solvents generate high concentration of PbI6 (-) . We furthermore propose that all these plumbate ions may act as structural defects determining electronic properties of the photovoltaic films.

Temperature-modulated space-charge-limited-current spectroscopy (TMSCLC) is applied to quantitatively evaluate the density of trap states in the band-gap with high energy resolution of semiconducting hybrid lead halide perovskite single crystals. Interestingly multicomponent deep trap states were observed in the pure perovskite crystals, which assumingly caused by the formation of nanodomains due to the presence of the mobile species in the perovskites.

Versatile approaches to nanoparticle synthesis offer unprecedented opportunities for the development of optoelectronics, photonics, as well as bio sciences. With the current advancement of hybrid organic-inorganic metal halide perovskites, the next step is to expand their field of applications via utilization of functional and modifiable ligand chemistry. Here, we present a ligand assisted reprecipitation approach for highly luminescent perovskite nanoparticle synthesis using for the first time L-lysine and L-arginine for surface passivation. These nanoparticles exhibit emission within a narrow bandwidth of the visible spectrum and photoluminescence quantum yield close to 100%. Additionally, preferential ligand orientation is achieved via amino acids α-amino group blocking which results in blueshifted emission as well as smaller and more uniform particle size. These experimental results demonstrate the effectiveness of naturally occurring proteinogenic amino acids as surface ligands and offer possibilities for versatile modification of perovskite nanoparticle properties via well-studied amino acid chemistry.