To make a Sn precursor, I put SnCl2 in IPA and stirred it for about a day. Sometimes it would become opaque and sometimes transparent. It would be transparent at first, then become opaque, and then become transparent again after some time. I wonder why that is! And after spin coating the precursor solution, I made SnO2 through heat treatment and used it as a hole blocking layer, but when it was opaque (very small particles were visible inside the precursor), the performance was not good, and when it was transparent, the performance was good. Is there any connection between this? All cleaning was done thoroughly.