Effective host materials are required to improve the performance of phosphorescent organic light-emitting diodes (PhOLEDs). Herein, a series of triazine-dibenzofuran-based n-type host materials, DBT1–DBT4, was prepared by varying the substitution position of dibenzofuran. The photophysical, thermal, and electrochemical properties as well as the device performance of these materials were investigated to establish structure–property relationships. The results demonstrated that the substitution position of dibenzofuran significantly affects the chemical structure, resulting in differences in electrochemical and photophysical properties. All the developed materials were utilized in green top-emitting PhOLEDs as an n-type host material mixed with a p-type host (BPCz), and their electroluminescence (EL) properties were assessed by systematically analysing 18 devices. Among them, the green PhOLEDs using a mixed host of DBT4/BPCz (DBP4-III) displayed the best EL performance with a high current efficiency up to 131.98 cd A⁻¹, an external quantum efficiency up to 30.90%, and a power efficiency up to 105.44 lm W⁻¹ with a device lifetime (T₉₅) of 180 h at 10 000 nits. These findings are expected to aid in the development of improved n-type host materials for highly efficient top-emitting PhOLEDs with long operational lifetimes.