OPTICAL-PROPERTIES OF CDS NANOCRYSTALLINE FILMS PREPARED BY A PRECIPITATION TECHNIQUE

CdS semiconductor films of different crystalline size have been grown by a precipitation technique. The crystalline sizes were controlled by the reaction time period, pH/temperature of the solution and thicknes s of the deposit. From the optical absorption, the band gap of bulk-Cd S is found to be 2.405 eV and is increased to 2.97 eV for nanocrystall ine samples of average crystalline size 5.0 nm estimated from the blue shift. AFM analysis were performed to estimate the average crystallin e size. Photoluminescence studies of CdS nanocrystalline samples show a red shift. The intensity of red luminescence(similar to 1.8 eV) decr eases and its peak position shifts to the lower energy upon increasing the particle size. Photovoltage as a function of crystalline size/ban d gap has been studied using a photoelectrochemical solar cell configu ration Ti/CdS/S2-, S-2(2-)/Pt. (C) 1998 Elsevier Science S.A. All righ ts reserved.