A curable organopolysiloxane composition, a Light Emitting Diode (LED) encapsulant and a semiconductor device, employ a curable organopolysiloxane composition containing a branched organopolysiloxane bearing alkenyl groups and aryl groups, a linear organopolysiloxnae bearing terminal Si—H functionality, and a low molecular weight component having at least one alkenyl group. As an encapsulant, the composition displays improved stability.