The white organic light emitting devices (OLEDs) with a structure of ITO/NPB/mCP/(t-bt)2Ir(acac)/mCP/FIrpic/mCP/TPBi/Mg∶Ag were fabricated using a blue and yellow phosphorescent dyes of bis[(4,6 diflourophenyl) pyridinato N,C2’)](picolinato) Iridium(III) (FIrpic) and bis[2-(4-tertbutylphenyl)benzothiazolato N,C2,]iridium (acetylacetonate)[(t bt)2Ir(acac)] as ultrathin layers, respectively.The performance of white OLEDs has been optimized by adjusting the film thickness of (t bt)2Ir(acac) and Firpic.The results showed that a pure white organic light emission was obtained with a current efficiency of 13.08 cd/A and a power efficiency of 7.21 lm/W.The CIE (Commissions Internationale De L’Eclairage) coordinates near (0.33,0.33) was observed at 9 V with a slight variation of (±0.08,±0.08) in a wide range of voltages.The high power efficiency and stable electroluminescence were attributed to the confining emission zone function of direct carrier trapping in the ultrathin layers.