The second tier of OLED Light-Emitting Layer Host Material segmentation classifies materials by functional type, each underpinning distinct performance envelopes. Phosphorescent hosts constitute the largest share, typically 45 %, because they enable near‑100 % internal quantum efficiency by harvesting both singlet and triplet excitons, a prerequisite for high‑end displays. Thermally activated delayed fluorescence (TADF) hosts represent roughly 30 %, offering comparable efficiency without rare‑metal catalysts, thereby reducing cost and improving sustainability for mid‑range panels. Fluorescent hosts account for about 15 %, remaining viable in low‑cost lighting and monochrome applications where simplicity and lower triplet‑related degradation are valued. Mixed‑host systems—blends of phosphorescent and TADF or fluorescent components—cover the remaining 10 %, engineered to balance charge transport, exciton confinement, and operational stability across diverse device architectures. The proportional weight of each type reflects R&D investment, material pricing, and end‑use specifications, collectively shaping the total addressable market and informing supply‑chain allocation.