Investigation of formamidinium and guanidinium lead tri-iodide powders as precursors for solar cells

•The investigation of formamidinium and guanidinium lead iodide powders is reported.•Photoluminescence properties of guanidinium containing system are demonstrated.•Fabrication of devices starting from the dissolution of the prepared powders.

Formamidinium and guanidinium lead tri-iodide powders (FAPbI3 and GUAPbI3 respectively) were prepared by self-organization processes in solutions. The XRD analysis detected the formation, at room temperature, of a trigonal structure (α-FAPbI3, space group P3m1), of a (non-perovskitic) hexagonal structure (δ-FAPbI3, space group P63mc) for FAPbI3, and the presence of orthorhombic (space group Pnma) and hexagonal structures for GUAPbI3 respectively. The morphological investigation revealed the growth of aggregated (α-FAPbI3 phase) and stripe-like crystallites (GUAPbI3) respectively. The infrared spectra (IR) confirmed the strong influence of additional C–N bonds on vibrational properties of GUA-containing system. Optical absorption measurements indicated that α-FAPbI3 and GUAPbI3 systems reveal direct energy band gaps of 1.42 eV and 1.92 eV respectively at room temperature. Photoluminescence measurements revealed emissions in the infra-red (IR) (for α-FAPbI3) and visible (Vis) ranges (for GUAPbI3). Films formation of GUAPbI3 was demonstrated, and solar cells devices were fabricated with average power conversion of 0.3%.

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