Optical measurements on doped C-60 films provide evidence for a transition from a high temperature conducting phase to a low temperature insulating phase in quenched Rb1C60 and K1C60 compounds, while Cs1C60 did not exhibit this behavior. For slow cooled samples our study confirms earlier results indicating phase separation of K1C60 to K3C60 and C-60, and the formation of a new Rb1C60 phase at low temperatures. Upon slow cooling Cs1C60 behaves similar to Rb1C60.