To study the influence of host material on the performances of organic light emitting diodes, a series of single-emitting layer (EML) devices are prepared by selecting energy-matching electron transport material Tm3PyP26PyB as electron-type host material and comparing it with single-EML devices prepared by using the bipolar host material CzSi. Additionally, TcTa, which has better hole transporting ability, is used as the first EML’s host material while Tm3PyP26PyB and CzSi are used as the second EML’s host materials, respectively, to prepare a series of double-EML devices for comparison. In comparison with Tm3PyP26PyB, CzSi has bipolar properties that make it superior in balancing holes and electrons and in broadening recombination zones. This allows better performance to be obtained from single-EML and double-EML devices. Consequently, the optimized single-EML device using CzSi host material has a maximum brightness, current efficiency, and power efficiency of up to 8634 cd/m ², 18.70 cd/A, and 16.78 lm/W, respectively; while the maximum brightness, current efficiency, and power efficiency of the optimized double-EML device with TcTa and CzSi host materials are up to 10770 cd/m ², 30.12 cd/A, and 30.52 lm/W, respectively.