Dramatic improvement of excitonic photoluminescence in metal halide films Review Article

So far, excitonic photoluminescence (PL) in metal halides (MHs) has exhaustively been studied by many workers, not only with the interest in the fundamental properties of excitons, but also with the expectation that excitonic luminescence in MHs is useful for application in optoelectronics because of its highly-light-emitting mechanism. In the actual MHs, however, excitonic PL is so weak that their excitonic luminescence is far beyond the scope of application—this is due to defect-rich problems native to MHs. Here we show dramatic improvements of excitonic PL in MHs recently achieved by two different methods, both of which employ simple techniques, i.e., solid-state chemical interaction/reaction (method 1) and amorphous-to-crystal transformation (method 2)—they are both applicable in several MHs. In the present paper, a systematic overview is given on the improvements achieved by method 1, together with a brief description of the improvements achieved by method 2.