Zero-dimensional (CH3NH3)3Bi2I9 perovskite for optoelectronic applications

Abstract

We present the preparation and characterization of solution processed lead free films of zero-dimensional methylammonium iodo bismuthate (CH3NH3)3Bi2I9 perovskite. Structural characterization reveals the formation of hexagonal micro-crystals with preferred growth orientation along the c-axis. The material exhibits a wide band gap of 2.9eV and upon optical excitation the photoluminescence emission is observed at 1.65eV (751nm). Photoelectron spectroscopy confirms the stoichiometry of the (CH3NH3)3Bi2I9 perovskite and yields an ionization energy of 6.24eV, while Raman spectra confirm the vibrational modes of the bioctahedral inorganic anion framework (Bi2I9)3− in the low wavenumber regime (<200cm−1) regime. Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TDDFT) are employed to evaluate the experimental results. We apply this novel bismuth-based hybrid perovskite in proof of principle simple heterojunction solar cell devices, which yield power conversion efficiencies of ~0.1%. Further enhancement is expected once the film morphology and device stack are optimized.