Low temperature excitonic spectroscopy study of mechano-synthesized hybrid perovskite

Photo-physical properties of mechano-chemically synthesized organic-inorganic hybrid perovskites have been investigated. CH3NH3PbBr3 nano-particles were prepared using the wet ball milling technique. Three emission peaks have been observed using low temperature photoluminescence spectroscopy. We assign these peaks to originate from free excitonic (FE) and bound excitonic emission and impurity level transition. FE peak energy increases linearly with temperature and a lattice phase change (orthorhombic to cubic) induces a sudden lateral shift after 110 K. However, the simultaneous presence of two phases has not been observed in this case. Greater activation energy is found in the mechano-chemically synthesized material rather than reported solution processed samples which indicates higher excitonic stability.