The OP552B from TT Electronics is a Phototransistor with Collector Emitter Voltage (Breakdown) 30 V, Collector-Dark Current 100 nA, Collector Emitter Voltage(Saturation) 0.40 V, Emitter Collector Voltage(Breakdown) 5 V, Power Dissipation 100 mW. More details for OP552B can be seen below.