Improving the efficiency of cadmium sulfide-sensitized titanium dioxide/indium tin oxide glass photoelectrodes using sil
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NANO EXPRESS
Open Access
Improving the efficiency of cadmium sulfide-sensitized titanium dioxide/indium tin oxide glass photoelectrodes using silver sulfide as an energy barrier layer and a light absorber Chong Chen1,2*, Yong Zhai1,2, Chunxi Li1,2 and Fumin Li1,2*
Abstract Cadmium sulfide (CdS) and silver sulfide (Ag2S) nanocrystals are deposited on the titanium dioxide (TiO2) nanocrystalline film on indium tin oxide (ITO) substrate to prepare CdS/Ag2S/TiO2/ITO photoelectrodes through a new method known as the molecular precursor decomposition method. The Ag2S is interposed between the TiO2 nanocrystal film and CdS nanocrystals as an energy barrier layer and a light absorber. As a consequence, the energy conversion efficiency of the CdS/Ag2S/TiO2/ITO electrodes is significantly improved. Under AM 1.5 G sunlight irradiation, the maximum efficiency achieved for the CdS(4)/Ag2S/TiO2/ITO electrode is 3.46%, corresponding to an increase of about 150% as compared to the CdS(4)/TiO2/ITO electrode without the Ag2S layer. Our experimental results show that the improved efficiency is mainly due to the formation of Ag2S layer that may increase the light absorbance and reduce the recombination of photogenerated electrons with redox ions from the electrolyte. Keywords: Silver sulfide nanocrystals; Titanium dioxide; Photoelectrodes; Efficiency; Recombination
Background Dye-sensitized photoelectrodes consisting of a wide band gap semiconductor film and a dye form the basis of many applications in photocatalytic, optoelectronic, and photovoltaic devices [1-10]. In photovoltaic applications, the photoelectrodes are typically titanium dioxide (TiO2) films, which are sensitized by an organic or inorganic dye [7,9,11]. In dye-sensitized photoelectrodes, the dye plays an important role in light absorption and charge transfer. Compared with organic dyes, semiconductor nanocrystals (i.e., inorganic dyes) with their size-tunable absorption and high molar extinction coefficient [12,13] are superior in thermal and photochemical stability. Due to these advantages of semiconductor nanocrystals, theoretically, semiconductor nanocrystal-sensitized solar cells may have a maximum efficiency of 44%, which is much higher than that of organic dye-sensitized solar cells [14]. * Correspondence: [email protected]; [email protected] 1 Henan Key Laboratory of Photovoltaic Materials, Henan University, Kaifeng 475004, People's Republic of China 2 School of Physics and Electronics, Henan University, Kaifeng 475004, People's Republic of China
So far, various types of inorganic nanocrystals such as CdS [15-17], CdTe [15,16], CuInS2 [18,19], Ag2S [20-24], and PbS [25,26] have been incorporated on TiO2 photoelectrodes as sensitizers to enhance the light absorption of the TiO2 photoelectrodes in the visible light region. Among single nanocrystal-sensitized TiO2 photoelectrodes, CdS-sensitized TiO2 photoelectrodes show a better photoelectric conversion performance. The efficiency of over 4% has been reported for CdS-sensitized TiO2 nanotube array photoelec
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