Study On The Double Perovskite Cs₂TiBr₆ Solar Cells

In recent years,the double perovskite structure A₂B’B"X₆ is expected to be promoted to commercial production as an alternative to ABX₃-type perovskite.The reason is that A₂B’B"X₆type perovskite does not contain lead ions,and has been proven to have good stability.Particularly,the double perovskite Cs₂TiBr₆ has been reported to possess excellent photovoltaic properties.Therefore,the specific research of this thesis is as follows:（1）The Cs₂TiBr₆ powder was synthesized by a full aqueous solution process and it was demonstrated to be highly unstable in ambient air.To reveal the decomposition mechanism,the individual investigations on its oxygen,moisture,thermal,and light stability were conducted.It is found that both oxygen and moisture are factors leading to the decomposition of Cs₂TiBr₆ powder in ambient air,and the moisture plays a major role in the decomposition process.Notably,it is demonstrated for the first time that Cs₂TiBr₆decomposes to amorphous TiO₂ under both individual oxygen and moisture conditions,and its decomposition products under moisture conditions also include（H₂O）_0.25·Ti₄O₇（OH）₂.Regarding the thermal stability,Cs₂TiBr₆ powder remains stable after 230 h of heating at 100°C,and the thermogravimetric analysis shows its intrinsic thermal decomposition temperature ranges from 400 to 600°C.Regarding the light stability,the Cs₂TiBr₆ powder remains stable after 100 h under the standard simulated one-sun AM 1.5 G irradiation condition.Further,it was demonstrated that the Cs₂TiBr₆film has the same excellent thermal and light stability as its powder.（2）The Cs₂TiBr₆ solar cell was designed using the numerical simulation software SCAPS-1D,and the hole transport layer material,electron transport layer material,back contact material,absorbing layer thickness,absorbing layer bulk defects,interface defects,and operating temperature were investigated.The predicted structure FTO（500 nm）/Sn O₂（30 nm）/Cs₂TiBr₆（100 nm）/PTAA（30 nm）/Au obtained the Voc of 1.62 V,the Jsc of 10.70 m A/cm~2,the FF of 84.33%,and the PCE of 14.61%at 300 K.It demonstrates the potential of double perovskite Cs₂TiBr₆ material in the photovoltaic field and provides a reference for the future design of Cs₂TiBr₆-based double perovskite solar cells.（3）Cs₂TiBr₆ nanocrystals solution was prepared by hot-injection route with rectangular and circular shapes,an average particle size of 22.57 nm,and a crystalline surface spacing d of 0.148 nm.Subsequently,the solution method was used to prepare three kinds of dense and homogeneous Cs₂TiBr₆ films with～54μm,～9μm,and～1μm thicknesses,respectively.Based on the films,the Cs₂TiBr₆ solar cell with structure of ITO/Sn O₂/Cs₂TiBr₆/Spiro-OMe TAD/Ag were prepared.The solar cell with～1μm film has the Voc of 0.59 V,the Jsc of 10.88μA/cm~2,the FF of 26.94%and the PCE of0.00171%.