ABSTRACTChemical spray pyrolysis (CSP) is a technique in which compounds of the constituents of the thin film to be fabricated are dissolved in an aqueous solution which is subsequently sprayed onto a heated substrate using nitrogen as the atomizing gas. At relatively low substrate temperatures (150–400°C) chemical reactions take place in which film formation of the desired compound occurs concomitantly with the release of volatile chemical reactants. The technique has advantages that include: (1) simplicity, (2) low cost and simple equipment, (3) the ability to prepare films over large areas with various shapes with relative ease and (4) the possibility of varying the physical properties through chemical means in known ways at modest temperatures. Results on the preparation of CuInSe2 which is a defect dominated semiconductor of technological interest are presented. Both n- and p- type materials were prepared with resistivities varying from 10−2 – 104 ohm-cm illustrating the use of the control of solution chemistry to produce films with reproducibly controlled properties.