The invention provides a kind of preparation method of ammonium thioglycolate, comprising the following process steps: (1), sodium thioglycolate impurity removal: (2), vacuum distillation: the lower sodium thioglycolate obtained in step 1 is distilled under vacuum: ( 3) Filtration: The mixture cooled in step 2 is subjected to low-temperature vacuum filtration to remove solids to obtain a relatively transparent high-concentration sodium thioglycolate solution; (4) acidification: the transparent thioglycolic acid solution obtained in step 3 is added dropwise to the sodium solution , acidification of sodium thioglycolate to obtain a relatively pure thioglycolic acid solution; (5), ammoniation: to obtain thick ammonium thioglycolate; (6), filtration: a small amount of impurities are removed by vacuum filtration of the solution obtained in step 5, and pink ammonium thioglycolate is obtained product. The invention utilizes the sodium thioglycolate by-produced in the production of thiocarbamate to obtain the product through a series of physical and chemical reactions, and has low cost and good application effect.
We investigated the effect of excess PbI2 in the precursor solution on the structural and optical properties of a model hybrid perovskite methylammonium lead iodide (MAPbI3) thin film. We found that excess PbI2 in the precursor solution resulted in crystalline PbI2 in the final film located at the grain boundaries. From UPS we found that this crystalline PbI2 has no direct effect on the electronic structure of MAPbI3. In contrast, temperature-dependent absorption measurements reveal a systematic change in the temperature dependence of the exciton binding energy in perovskites. We also observe a decrease in the critical temperature and the concomitant blurring of the tetragonal-orthorhombic phase transition as a function of excess PbI2. Therefore, our results contribute to a better understanding of the exact role of PbI2 in the perovskite layer and pave the way for the customized design of perovskite solar cells.