Luminescent Cu(I) complexes have recently attracted increasing attention from researchers as promising environmentally friendly emitters due to their structurally tunable photophysical properties. Typically, Cu(I) derivatives exhibit long-lived phosphorescence due to metal-ligand charge transfer (MLCT) and/or intraligand transitions. At the same time, these complexes can exhibit thermally activated delayed fluorescence (TADF), which allows achieving 100 % internal quantum efficiency. Until recently, most examples of the TADF mechanism were found for platinum metal compounds, the cost and prevalence of which do not allow for the widespread introduction of devices based on them into production. It is known from the literature that TADF luminescent Cu(I) complexes can be conditionally divided into two main classes: mononuclear and polynuclear complexes, with the latter being much more numerous. Mononuclear Cu(I) TADF complexes include predominantly cationic and neutral tetracoordinated compounds, mainly belonging to the [Cu(N^N)2] and [Cu(N^N)(P^P)] types. However, in 2011, Hitomi Ohara proposed rather simple mononuclear Cu(I)-halide complexes, [CuX(PPh3)2(L)] (X=halide ion, PPh3=triphenylphosphine, L=N-heteroaromatic ligand), demonstrating extremely intense luminescence realized by the TADF mechanism. Using this approach, in the present work, 3-pyridin-4-yl-5-(4-chlorophenyl)-1H-1,2,4-triazole was selected as an N-heterocyclic ligand for the creation of new representatives of mononuclear TADF–copper(I) phosphors. The synthesized complexes have fundamentally different spatial structures, despite the difference only in the halogen ion during the synthesis of the compounds. Copper(I) bromide forms a mononuclear complex of monoclinic syngony in the space group P21/n, while copper(I) iodide is a binuclear complex of triclinic syngony with a flat core of the rhombic form Cu2I2 in the space group P‾1.