Single layer electroluminescent (EL) devices based on soluble p type polymer PDDOPV doped by n type soluble polymer PPQ are successfully fabricated.Comparing with single layer devices of pure PDDOPV,the turn on voltage of doped single layer devices is drop from 4.5 V to 2.6 V at the same applied voltage,the current is higher but still at the same order of magnitude,the brightness and luminescent efficiency are both enhanced more than one order of magnitude.At 10 V,the current,brightness and luminescent efficiency of devices of blends are 1.95,30.9 and 16.0 times of those of devices of pure PDDOPV respectively.The remarkable enhancement of doped devices is attributed to the reduction of injection barrier of minority carrier and enhancement of minority carrier injection caused by the doping PPQ in PDDOPV.This result demonstrates that it is an effective way to improve the device performance by doping n type polymer in p type polymer.