Study On The Preparation And Properties Of CsPbI₃ Light Absorption Layers For Perovskite Solar Cells

With the continuous development of the economy,the energy crisis and environmental pollution have become important issues affecting human life.Among many new energy sources,solar energy is regarded as a clean and safe energy source.Therefore,solar cells have become one of the promising research directions.Perovskite materials are widely used in perovskite solar cells due to their high absorption coefficient,adjustable forbidden band width,and high carrier mobility.At present,the power conversion efficiency?PCE?of perovskite solar cells has exceeded25%,which is comparable to that of silicon-based solar cells.Perovskite solar cells are expected to become ideal high-efficiency,low-cost photovoltaic devices.In recent years,inorganic perovskite solar cells have attracted attention because of the hope of obtaining better thermal stability.Among inorganic perovskites,the perovskite-structured CsPbI₃ has attracted attention in inorganic perovskite solar cells because of the suitable band gap width.Perovskite solar cells are mainly composed of a perovskite light absorbing layer,an electron transport layer and a hole transport layer.The high quality perovskite absorption layer can not only increase the absorption of light,but also inhibit the recombination of carriers,and promote the charge extraction process of electron transport layer and hole transport layer.Therefore,the quality of the perovskite light-absorbing layer film is important for the entire perovskite solar cell.In this paper,the light absorption layer in the inorganic CsPbI₃ perovskite solar cell is taken as the research object,and two aspects of work are done:1.We used lead acetate?Pb?AC?₂?and lead iodide?PbI₂?as lead sources,while using ethylenediamine iodide?EDAI₂?as an additive,we mixed EDAI₂ in the form of EDAPbI₄ solution into the CsPbI₃ precursor solution to prepare calcium CsPbI₃ thin film with titanium structure.The study found that the CsPbI₃ film prepared with Pb?AC?₂ as the lead source is denser,more crystalline,and larger in particle size.And by space charge limiting current?SCLC?characterization,it was found that the defect density of CsPbI₃ thin films prepared with Pb?AC?₂ as the lead source was lower.We assembled the CsPbI₃ thin films prepared by the two lead sources into TiO₂ as the positive device of the electron transport layer/CsPbI₃ light absorption layer/Spiro-OMeTAD hole transport layer.The PCE of the device was 10.4%?PbI₂?and12.9%?Pb?AC?₂?.Photoluminescence?PL?and device impedance studies have shown that the CsPbI₃ light-absorbing layer prepared based on Pb?AC?₂ as a lead source is more beneficial to the charge transport process and can effectively suppress the charge recombination process.These results indicate that Pb?AC?₂ is promising as another lead source for the preparation of inorganic perovskite solar cells.2.The CsPbI₃ perovskite composition is controlled by an additive method to prepare a high-quality perovskite film.With guanidium iodide?GuaI?as an additive,GuaI was incorporated into the CsPbI₃ perovskite precursor solution as a GuaPbI₃solution.By regulating the crystal growth of CsPbI₃,a CsPbI₃ thin film with almost no pinhole,dense,and high crystallinity perovskite structure was prepared.The process of light absorption,charge transport and charge collection of the CsPbI₃light-absorbing layer is effectively improved,thereby improving the performance of the CsPbI₃ perovskite solar cell.By optimizing the amount of GuaPbI₃ doped,we increased the average PCE of upright devices based on the TiO₂ electron transport layer,CsPbI₃ light absorption layer,and Spiro-OMeTAD hole transport layer from 8.6%to 11.1%.