There are no known grass-type pokemon which photosynthesize energy primarily from starlight, for starlight can not compare to the brightness of the Sun. There is, however, one bug-type pokemon which does exactly that. Ledian are quite unusual in this respect; their larval form of Ledyba subsist on smaller bug pokemon such as Caterpie, and other bugs eat the leaves and nectar of grass-types, but Ledian, unable to process sunlight or eat food, rely on the strange wavelengths of distant stars.
Oddly enough, despite their energy source being easiest by far to receive at night, Ledian are a morning pokemon, and many have speculated as to the reasons for this odd behavior. Grass-type pokemon are diurnal, and their movement is based on spreading pollen, finding good soil and open sky, or in some cases such as Victreebel, supplementing their sunlight with living food. Ledian, however, do none of these things; their mating is in the manner of insects, they do not eat, and they can not filter starlight from sunlight to absorb it in the daytime.
The only explanation which has been ventured for the morning activity of Ledian is one which is not based on evolutionary fitness at all. Ledian, it is argued, are used to an active life as Ledyba, and like humans are capable of feeling boredom. Therefore, after the nights restore their energy, they spend their mornings engaging in whatever activities they enjoy, until they tire in the afternoon and fall asleep once again. There are those who have not accepted this, who believe some hidden purpose for their daytime activity will be eventually found, but most Ledian specialists see this as just another piece of evidence that pokemon are more complex and intelligent than we tend to realize.