Preparation Of ATO Transparent Conductive Thin Film And The Thin Film Solar Cell Prototype Device

Thin film solar cells have attracted wide attention for their notable advantages.Among them,copper zinc tin sulfide?CZTS?device is one of the promising solar cells for its merits of high photoelectric conversion efficiency and low environmental hazardous,antimony selenide?Sb₂Se₃?thin film solar cells permit a high device efficiency and simple preparation process,both of them have become the research hotspots in recent years.However,the cost,efficiency and stability of thin film solar cells still need to be optimized.Looking for a transparent conductive electrode with excellent performance and favorable matching character is one of the effective ways to improve the energy conversion efficiency.Due to the prominent advantages as low cost,abundant resources and non-toxicity,ATO thin film has currently become one of the potential substitutes for ITO film.However,the structure,optical and electrical properties of ATO films will be obviously affected by a variety of factors including the crystallinity,valence state distribution of Sb element,carrier trasportation and so on,which makes it hard to prepare ATO films with both high transmittance and low resistivity.In this thesis,ATO thin films prepared by radio frequency magnetron sputtering after optimizing the processing parameters such as deposition temperature,oxygen flow rate are used as cathodes of the inorganic thin film solar cells to improve the photoelectric conversion efficiency.The relationship between composition,microstructure,Sb⁵⁺/Sb³⁺ratio and the physical properties have also been investigated.CdS layer is easy to be decomposed at high temperature,so we discussed the effects of oxygen flow rate and sputtering power on the microstructure,composition,optical and electrical properties of ATO thin films at a low temperature of 200 ^oC.The results show that the increase of oxygen flow rate can promote the lattice integrity of oxide films,which will make the visible light transmission increase.Proper oxygen flow rate is helpful to the conversion of Sb³⁺to Sb⁵⁺,which can contribute to the carrier concentration and finally results in a low resistivity.With the increase of the sputtering power,the film particles have more energies to move,which makes the film a better crystallinity,then lead to a higher carrier mobility.When the oxygen flow rate is 5 sccm,the sputtering power is 250 W,ATO film is observed that has a lower resistivity of 6.84×10^-3?·cm,a high transmittance of 89.96%.Subsequently,CZTS thin film solar cell devices with ATO film as cathode achieves an optimal photoelectric conversion efficiency of 1.66%,but the internal resistance of the device is still high and it has a poor stability in the high temperature and high humidity environment.It is an efficient way to improve the carrier concentration and mobility of ATO films by increasing the deposition and annealing temperature.Therefore,the process parameters of ATO films which will be applied into the Sb₂Se₃ devices are further optimized.The results show that with the increase of deposition and annealing temperature,the Sb⁵⁺/Sb³⁺ratio and crystallinity of ATO thin films are obviously enhanced.The lattice integrity of ATO thin film is raised and the defects decrease with the increase of annealing temperature,making it a high visible light transmittance.When the annealing temperature is up to 550 ^oC,the increase of carrier concentration makes the resistivity decreased to 7.5×10^-3?·cm.ATO film prepared at500 ^oC,annealed at 550 ^oC has the lowest resistivity of 2.82×10^-3?·cm,a transmittance of 85.45%,the quality factor is 4.7×10^-3?^-1.Finally,Sb₂Se₃ thin film solar cell device with ATO film as cathode achieves an optimal photoelectric conversion efficiency of 0.63%,but the internal resistance of the device is still high and the preparation process of Sb₂Se₃ is not mature enough,the efficiency of ATO/Sb₂Se₃ thin film solar device is not very well.