Increasing the Structural Rigidity and Quantum Yield of Highly Emissive Hybrid Antimony Chlorides Using a Diverse Set of Solvent Guests

0D organic–inorganic antimony halides have attracted increasing attention due to the non-toxicity, high stability, and superior photoluminescence quantum yield (PLQY). Here, a series of hybrid antimony chlorides with the same organic cation ethyltriphenylphosphonium (Ph 3 EtP + ), including non-emissive (Ph 3 EtP) 2 Sb 2 Cl 8 and nine (Ph 3 EtP) 2 SbCl 5 -based emissive compounds, are synthesized and characterized. These emissive compounds are namely, the guest-free (Ph 3 EtP) 2 SbCl 5 and (Ph 3 EtP) 2 SbCl 5 ·guest (guest = glycol, acetic acid, methanol, ethanol, n-propanol, i-propanol, acetone, and acetonitrile). The solvent used can alter the coordination mode of Sb because the solvation effect affects the reactivity of the anions ([SbCl 4 ] − and Cl − ), leading to the formation of either A 2 Sb 2 Cl 8 or A 2 SbCl 5 . The solvents can be even incorporated into the crystal structure, where stronger interaction with [SbCl 5 ] 2− leads to higher temperature of the escape of the solvent. The guest molecules could increase the structural rigidity of [SbCl 5 ] 2− via hydrogen bonding and dipole–dipole interactions, which tends to reduce the room-temperature photoluminescence (PL) Stokes shift and temperature-dependent PL shift by decreasing the [SbCl 5 ] 2− deformability, along with enhanced PLQY from 81% in guest-free to near-unity in (Ph 3 EtP) 2 SbCl 5 ·glycol. This work shows that targeted synthesis and diversified choices of solvents provide an efficient tool to generate steady variations in hybrid emissive materials for optoelectronics.