NOVELTY - Preparation of a benzodithiophene compound involves reacting at least one monohalogenated dithiophene compound with at least one internal alkyne in the presence of at least one catalyst containing palladium and of at least one co-catalyst containing copper in oxidation state +1.    USE - For the preparation of benzodithiophene compounds (claimed) used in the construction of photovoltaic devices (or solar devices) such as, e.g. photovoltaic cells (or solar cells), photovoltaic modules (or solar modules) on rigid and flexible supports; as a constituent unit of luminescent solar concentrators (LSCS); and as a precursor of monomeric units in the preparation of semiconductor polymers.    ADVANTAGE - The method exhibits relative synthesis easiness, a low production cost, a reduced weight of the relative organic photovoltaic devices (or solar devices), and allows the recycling of organic materials at the end of the life-cycle of the organic photovoltaic device (or solar device) in which the compound formed by the method are used. The process allows benzodithiophene compounds to be obtained with good yields (i.e. yields of 70% to 80%), avoids lengthy reaction times (preferably times of 15 hours to 72 hours) with a consequent decrease in the process costs and avoids degradation of compounds obtained. The method causes reduction in the number of synthetic steps with a relative reduction in the processing times and process costs; uses monohalogenated starting products which are generally more economical and more stable than the corresponding dihalogenated compounds; uses internal alkynes which are more economical and more stable than diboron esters of internal alkenes; exhibits greater safety conditions (e.g. absence of corrosive and/or flammable reagents such as e.g. titanium tetrachloride, lithium diisopropylamide (LDA)) for both the health of the operators and also from an environmental point of view; is applicable at relatively low temperatures and has short reaction times thus avoiding the possible degradation of the product obtained and higher process costs. The process allows benzodithiophene compound to be obtained with high yields (i.e. yields approximately 85%).    DETAILED DESCRIPTION - Preparation of a benzodithiophene compound of formula (I) involves reacting at least one monohalogenated dithiophene compound of formula (II) with at least one internal alkyne of formula R1-C?=C-R2 (III) in the presence of at least one catalyst containing palladium and of at least one co-catalyst containing copper in oxidation state +1 of formula CuX1 (IV).    R1 and R2=hydrogen atom, a linear or branched 1-20C alkyl, cycloalkyl optionally substituted, aryl optionally substituted, or heteroaryl optionally substituted;    X=halo selected from I, Cl, or Br;    X1=halo selected from I, Cl, or Br.