Preparation of CuInSe2 and CuInGaSe2 nanoparticles and thin films for solar cells applications (2010)

In present work, thin films and nanoparticles of copper selenide (Cu2-xSe), indium selenide (In2Se3), copper indium diselenide (CuInSe2), copper gallium diselenide (CuGaSe2) and copper indium gallium diselenide (CuIn(1-x)GaxSe2) were deposited from diisopropyldiselenophosphinatometal complexes Mx[iPr2PSe2]y (M = Cu, In, Ga). Thin films were deposited onto glass substrates by AACVD method whereas nanoparticles were grown by colloidal method which involved thermal decomposition of precursors in HDA/TOP system at desired growth temperature. The semiconductor thin films and nanoparticles obtained were characterized by UV-Vis spectroscopy, X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis. Thin films of copper selenide were deposited at temperatures ranging from 300 to 475 �C, using copper complex [Cu4(iPr2PSe2)4] as single source precursor (SSP). Berzelianite phase of Cu2-xSe (ICDD pattern 00-006-680) with predominantly triangular morphology was deposited at 350 and higher temperatures whereas thermal degradation of precursor in HDA/TOP system resulted in growth of colloids having 15 � 2.5 nm size. AACVD process involving In(iPr2PSe2)3 as SSP yielded uniform and well adhered films of ?-In2Se3 (ICDD pattern 00-040-1407) having cylinderical morphology. Bandgap of the films deposited at 400 �C was found to be 1.82 eV. Nanoparticles representing hexagonal phase of In2Se3 (ICDD pattern 00-012-0117) were obtained by degradation of this precursor in HDA/TOP at 270 �C. Size of the nanocrystals was found to be 5.0 nm (� 1.1). Copper indium diselenide (CuInSe2) thin films were deposited from 1:4 molar equivalents of [Cu4(iPr2PSe2)4] and [In(iPr2PSe2)3] precursors, respectively at temperatures ranging from 350 to 500 �C. Tetragonal phase of CuInSe2 (ICDD pattern 01-075-0107) was deposited and the films had an optical bandgap of around 1.17 eV. Similarly, thermolysis of 1:4 molar equivalents of [Cu4(iPr2PSe2)4] and [In(iPr2PSe2)3] precursors in HDA/TOP at temperatures ranging from 120 �C to 210 �C yielded monodispersed spherical particles. Size of the nanoparticles obtained showed strong dependance upon the growth temperature and reaction duration. Higher growth temperatures and longer reaction durations resulted in formation of larger nanoparticles. Tetragonal phase of chalcopyrite CuGaSe2 (ICDD pattern 00-035-1100) was deposited from AACVD of 1:4 molar equivalents of [Cu4(iPr2PSe2)4] and [Ga(iPr2PSe2)3] precursors at 400 - 500 ?C. Similarly, thermolysis of 1:4 molar equivalents of these precursors in HDA/TOP at 250 ?C yielded polycrystalline tetragonal chalcopyrite nanocrystals of CuGaSe2. Thin films of CIGS material were deposited at temperatures ranging from 300 to 500 �C by using different molar equivalents of copper, indium and gallium precursors. Best films were deposited and by using 1:2:2 molar equivalents of copper, indium and gallium precursor, respectively at 450 ?C. Colloidal synthesis of CuIn(1-x)GaxSe2 nanoparticles was also carried out by thermolysing different molar equivalents of copper, indium and gallium precursors in HDA/TOP at 250 ?C. Tetragonal chalcopyrite phase of the material was deposited in all cases. It was possible to tune the In/Ga ratio across the whole range of stoichiometric compositions with value of x ranging from 0 to 1 using this approach. Different stoichiometric compositions of CIGS nanoparticles grown in the present work include CuIn0.81Ga0.19Se2, CuIn0.68Ga0.32Se2, CuIn0.54Ga0.46Se2, CuIn0.47Ga0.53Se2, and CuIn0.19Ga0.81Se2. Size of the nanoparticles was found to be around 14 nm with standard deviation of 2.21 nm.