Optical exciton features in structurally diverse phenyl group-based inorganic–organic hybrid semiconductors

Abstract

A novel series of inorganic–organic (IO) hybrid semiconductors with varying crystal dimensions and structural reorganizations, arising from the unusual conformation of organic ammonium cation (R–NH3)+ within the MX6 inorganic octahedral networks, are investigated. Here, we report the systematic investigations of exciton behavior in a new IO hybrid series resulted out of phenyl group-based R = (C6H5–(CH2)n–NH3)+ (n = 1–4) organic moieties interactions with inorganic lead iodide (PbI2). The resultant IO hybrid semiconductors of n = 1 and n = 2 show an infinitely extended corner-sharing PbI6 octahedral 2D network, resembling natural multiple quantum wells, whereas the rest show staggered with edge sharing layered networks. Consequently, these hybrids demonstrate strong room-temperature Mott-type excitons having structural dependency. One-photon (1PA, ħω ≥ Eg) and two-photon (2PA, 2ħω ≥ Eg) absorption-induced photoluminescence (PL) studies highlight the presence of different types of excitons associated with variations in their bandgaps. The comprehensive analysis of transient absorption studies and PL spectral mapping reveal many important features of exciton behavior, specifically about their structural dependency, excited-state charge carrier dynamics, and relaxation pathways.