Effect of Cu/In Ratio in Crystal Growth of CuInSe2 Thin Films Fabricated by Reduction and Selenization Using Cu and In2O3 Paste Materials

Chalcopyrite CuInSe2 thin films were formed from paste precursors including Cu and In2O3 fine particles. The compositions of the pastes were In- and Cu-rich. Paste was coated on Mo/soda-lime glass by screen printing. The precursors were annealed at 450 °C under N2:H2 (97:3) ambient to reduce them. The reduced films consisted of the Cu11In9 and In phases. The reduced precursor showed granular shape and poor adhesion with the Mo layer because the melting point of Cu11In9 was about 300 °C and Cu11In9 does not wet with Mo. The reduced precursors were annealed at 600 °C under Se and Ar ambient to form the CuInSe2 thin films. The In-rich CuInSe2 thin film consisted of small grains. The Cu-rich CuInSe2 thin film was dense and consisted of large grains of about 3 µm.