| Energy is nowadays the symbol of the level of the social development, the sourceof solar energy is inexhaustible with stability and high security, which has largerpotential than other renewable energy in the technology, which fully showed that solarenergy is one of the main energy in the future. And in the utilization of solar energy,in addition to the use of light and heat, the main idea is the photovoitaic powergeneration, through the composite of P-type and N-type semiconductor material, theycan form P-N junction barrier in their interface, and prompt photoinducedelectron-hole pairs are effectively separated, therefore, the semiconductor materialswith different properties have been widely studied by scientists.Cadmium telluride (CdTe) is an P-type semiconductor material with band gap of1.45eV at room temperature, which is a direct transition band structure, it is veryclose to optimal energy gap of solar cells needed, it’s absorption coefficient is verystrong and can effectively absorb the visible light energy. Meantime, it is a goodphotovoitaic material with high theoretical conversion efficiency (28%), therefore,CdTe is an ideal adsorber material for high-efficiency, lawcost thin filmpolycrystalline. Cadmium sulfide (CdS) is a direct n-type semiconductor with a bandgap of about2.4eV and large absorption coefficient of104~105cm1, and we canobtain a low-resistance ohmic contact between CdS and SnO2.Electrochemical method has shown importance in the synthesis of films, since it is a low-temperature, low-cost, and facile technique with good control of thedeposited composition. Conventional production methods of CdTe solar are sputtering,evaporation proximity, thermal evaporation, chemical deposition,et al. In view ofimproving the performance of CdTe thin film solar cells and reduce process cost CdTethin film solar cell target for the realization of low-cost large-scale production, weshould requires new structural of designing CdTe solar cells and new researchpreparation.In this paper, we prepared CdTe films by electrochemical deposition on the Nisubstrate, the effects of electrochemical parameters on properties of electrodepositedCdTe films was studied, while CdS thin film growth by electrochemical on CdTesurface and their photoelectric properties have been researched. Finally we assembledinto a whole CdTe/CdS films battery module, and its properties were studied. Themain work is as follows:（1）We use an electrochemical method to synthesize CdTe films with differentmorphologies on a nickel substrate in cadmium sulfate and sodium tellurite acidicsolution system. Under the deposition potential of-0.50V, we prepared a uniform anddense CdTe nanorods array with good crystalline. Under deposition potential of-0.75V, we prepared cauliflower-like CdTe array thin films. CdTe films have asphalerite structure and preferential growth along the [111] direction. The film of twomorphology have photoelectric conversion efficiency of0.32%and0.61%,respectively. Also we found that the deposition potential can be adjusted to change theratio of CdTe compounds and adjust the bandgap of CdTe within a certain range. Byadding an appropriate amount of the cationic surfactant CTAB in the electrolyte, weprepared whole dense texture, flat sphalerite-type CdTe films. CTAB plays a veryimportant role in controlling the elements proportion of CdTe thin films in theelectrodeposition process, and we analyze its action mechanism.（2）We deposited CdS films on the surface of CdTe thin films in a cadmium sulfate,sodium thiosulfate and citric acid electrolyte system by electrochemical depositionmethod for the first time. The effect of reaction conditions on the ratio of the elements of the film, morphology, crystal structure and orientation of the crystal quality werestudied. We found that the citric acid in the electrolyte is conducive to obtain thedense CdS layer, and deposition potential can be adjusted by changing the ratio ofelements deposited CdS thin films, optimum deposition potential to get n-CdS thinfilm is-0.9V. The CdS film we prepared have a wurtzite structure and a [002]preferred orientation.（3）We prepared CdTe/CdS thin film solar cell module with a structure of thenickel foil/Ni2.86Te2/p-CdTe/n-CdS/CdS: In/ITO. We make both the CdCl2heattreatment and SnO2transparent conductive thin film grown by thermal evaporation inthe air process at the same time, we found that with the increase of heat treatmenttemperature, the efficiency of the battery module improved, the optimum heattreatment temperature is integrated450℃. The efficiency of solar cell we got was3.0%. We deposited the mixture of SnCl2and InCl3on the surface of CdS thermalevaporation, and grown In-doped SnO2transparent conductive film. The efficiency ofphotovoltaic cell module can reach to5.05%, which is higher significantly than thecase of SnO2transparent conductive film. The reason is that the formation of In-dopedSnO2: In can improves the conductivity of the film, while the In-doped to form CdSCdS: In layer of a low resistivity, make the collection efficiency of charge separationimprove.In this paper, we proposed CdTe/CdS solar cells with a structure of nickel foil/Ni2.86Te2/p-CdTe/n-CdS/CdS: In/ITO is a novel and simple method for preparing asolar cell. By further optimization of preparation parameters, there is considerableroom for improvement in the efficiency. |
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