Study On The Effect Of Potassium Doping On Aqueous Solution Processed Copper Indium Gallium Selenide Thin Film Solar Cells

The global energy problem is becoming more and more serious,and the development and utilization of new energy is a top priority.Therefore,solar cells have become a research hotspot of scientific researchers from all over the world.Copper indium gallium selenide（Cu（In,Ga）Se₂,CIGS）thin-film solar cells are promising low-cost thin-film solar cells for commercialization due to their high power conversion efficiency,good stability,and ability to be fabricated on flexible substrates.The preparation of CIGS thin film solar cells by the solution-processed can reduce the use of expensive vacuum equipment,improve the utilization rate of raw materials,and thus reduce the production cost,which is expected to overcome the cost problem that limits its large-scale application.The choice of solvent needs to consider whether it is cheap and easy to obtain and whether it is harmful to human body and the environment.Obviously,water is the most ideal solvent.In this thesis,the molecular precursor solution was prepared by using water as the solvent,copper indium gallium chloride and thiourea（TU）as the precursor compounds.The effects of different precursor compounds,the ratio of Ga/（Ga+In）and the selenization conditions on solar cells performance were systematically studied.The influence mechanism of KCl doping in the precursor solution on the preparation of CIGS thin-film solar cells by aqueous solution-processed was studied,and K-doped CIGS thin-film solar cells with an efficiency of 9.37%were obtained.The specific research contents and conclusions are as follows:（1）Preparation of CIGS thin film solar cells by aqueous solution-processed.The effects of precursor compounds,Ga/（Ga+In）ratio and selenization conditions on solar cells performance were studied.In the case of copper indium gallium chloride and TU as precursor compounds,the Ga/（Ga+In）feed ratio was 0.40,0.39 g selenium particles and selenization for 20 min,the prepared CIGS thin film solar cell has the best performance,and obtained a photoelectric conversion efficiency of 8.58%.（2）Influence of K doping on CIGS thin-film solar cells fabricated by aqueous solution.XPS results showed that the K-doped CIGS film formed a low-melting K-In-Se phase during the selenization process,which acted as a flux during the grain growth and acted as a selenium reservoir to provide selenium for the growth of CIGS grains.Compared with undoped CIGS films,K-doped films have larger grain size and denser films.The combination of the high-bandgap K-In-Se phase and higher Ga content increases the bandgap of K-doped CIGS.K-doping can also reduce the Urbach energy,suppress the band tail state,and improve the open-circuit voltage and fill factor,finally increasing the efficiency of K-doped CIGS thin-film solar cells by 33.1%to 9.37%.In this thesis,the effects of precursor compounds,Ga/（Ga+In）ratio and selenization conditions on solar cells performance were investigated,the photoelectric properties of CIGS thin-film solar cells were improved by K doping,and influence mechanism of K doping on CIGS thin-film solar cells fabricated by aqueous solution-processed was revealed,which provides a new idea for the commercial application of CIGS non-vacuum method.