Guanidine isothiocyanate is an organic compound with a molecular formula of C₂H₆N₄S. It is mainly used for denaturing and lysing cells, extracting RNA and DNA. In addition, guanidine isothiocyanate is also used in the field of solar cells to improve the crystallization performance of perovskite films and battery efficiency, battery stability, hysteresis effect and other issues, the following editor specifically introduces a method for preparing perovskite solar cells. 

1.Preparation of ZnO precursor: Dissolve 0.59g zinc acetate dihydrate in 25 mL methanol, and stir to dissolve in 65℃ water bath. Then 0.296g potassium hydroxide was dissolved in 13mL methanol solution under stirring at room temperature for dissolution, and the dissolved KOH solution was added dropwise to the zinc acetate solution, the reaction was continued for 2.5 hours, and then filtered and dried.

2.Spin-coating the ZnO precursor onto the surface of the transparent conductive electrode to form an electron transport layer.

3.An absorption layer is formed on the electron transport layer. Specifically:

① Dissolve PbI₂ in the mixed solution of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), the volume ratio of DMF to DMSO is 90:10～70:30, and PbI₂ in the mixed solution of DMF and DMSO, The concentration of PbI₂ in the mixed solution of DMF and DMSO is 1.1M.

② Add guanidine isothiocyanate, the molar ratio of guanidine isothiocyanate to PbI₂ is 1～4:50, stir to dissolve, and then spin-coat the mixed solution of PbI₂ and guanidine isothiocyanate on the electron transport layer, and proceed one baking, the first baking is sequentially baked at 60℃, 80℃ and 100℃ for 5 minutes.

③ Dip into the isopropanol (IPA) solution of CH₃NH₃I at a concentration of 10mg/ml, and then bake the second time form a hole transport layer on the absorption layer (the hole transport layer includes Sprio-OMeTAD, and the metal electrode includes Au electrode).A metal electrode is formed on the hole transport layer, and the transparent conductive electrode is FTO conductive glass.

The method belongs to the solution method, is simple to operate and easy to control, and the entire planar structure of the perovskite battery is prepared at a low temperature, and the maximum heat treatment temperature does not exceed 200℃. By introducing guanidine salt and thiocyanate ions, the photoelectric efficiency of the perovskite battery is effectively improved, and the stability of the battery is also greatly improved (the battery with guanidine thiocyanate can still maintain 80% of the initial efficiency after the same aging time). In addition, the introduction of guanidine salt and thiocyanate ions significantly improves the hysteresis of the battery (the efficiency difference of positive and negative scanning of the battery with guanidine thiocyanate is reduced to 3.09%).

References

CN 108987584 A  Perovskite solar cell and its preparation method.