The OP535B from TT Electronics is a Phototransistor with Collector Emitter Voltage (Breakdown) 15 V, Collector-Dark Current 100 nA, Collector Emitter Voltage(Saturation) 1.10 V, Emitter Collector Voltage(Breakdown) 2 V, On-State Collector Current 3.5 to 32.0 mA. More details for OP535B can be seen below.