FTA: > UCLA professor Yang Yang’s lab chock-full of coffee drinkers spent several years searching for a stability-enhancing additive to turn famously unstable perovskite PV cells into a useful product. Then, on a lark, Yang's graduate student Rui Wang suggested they try adding caffeine to the mix.

They tested different compounds for years before finding one that works - I don' think it would add much to the article to list every one of them.