NOVELTY - Preparation of a benzohetero(1,3)diazole compound (I) disubstituted with brominated heteroaryl groups comprises reacting at least one dihalogenated benzohetero(1,3)diazole compound (II) with at least one brominated heteroaryl compound (III).    USE - The process is useful for preparing benzohetero(1,3)diazole compound (I), which is useful in the synthesis of compounds useful in the construction of solar concentrators (preferably luminescent solar concentrators) and in the synthesis of photoactive polymers useful in the construction of photovoltaic devices (solar devices) comprising photovoltaic cells (or solar cells), photovoltaic modules (or solar modules), on both rigid or flexible supports, and as precursor of monomeric units in the synthesis of semiconductor polymers.    ADVANTAGE - The process involves a simpler synthesis and consequently lower production costs and disposal costs of the waste products. The process uses compounds, which are nontoxic to the environmental and to the operators, and the production costs and disposal costs of the waste products is less. The process uses brominated or chlorinated aryl compounds which are more economical and more stable with respect to iodinated aryl compounds.    DETAILED DESCRIPTION - Preparation of a benzohetero(1,3)diazole compound of formula (I) disubstituted with brominated heteroaryl groups comprises reacting at least one dihalogenated benzohetero(1,3)diazole compound of formula (II) with at least one brominated heteroaryl compound of formula (III).    W1 = O, S, or NR;    R = H or 1-20C-alkyl;    Y1 = S, O, Se or NRR2;    RR2 = H or linear or branched 1-30C-alkyl;    Z = N or CR2; either    R2 = H or linear or branched 1-20C-alkyl; and    R1 = cycloalkyl or aryl (both optionally substituted), H, linear or branched 1-20C-alkyl, linear or branched 1-20C-alkoxyl, polyethyleneoxyl group of formula (R-O-(-CH2-CH2-O)n-), -R1a-OH, -R1a-OR2a, -COR, COOR, -CHO or -CN; and    R3, R4 = H, linear or branched 1-20C-alkyl, linear or branched 1-20C-alkoxyl, -COOR or -CN; or    CR1R2, CR3R4 = saturated, unsaturated or aromatic cycle or polycyclic system containing 3-14C (optionally containing one or more heteroatoms comprising O, S, N, Si, P or Se);    n = 1-4;    R1a = linear or branched 1-20C-alkylene;    R2a = linear or branched 1-20C-alkyl or polyethyleneoxyl group of formula (R-O-(-CH2-CH2-O)n-); and    X = halo comprising Br (preferred) or Cl.