This Wikipedia page https://en.wikipedia.org/wiki/OLED#Material_technologies mentions a couple of molecules that are used for OLED.
The Ir-based compound has ~ 100% quantum efficiency, while Alq3 may ~30% quantum efficiency
But iridium is way more expensive than aluminum (2,550 USD per troy ounce ~ 82.00 USD per gram vs 2,846 USD per ton ). (Using cost of metal just a rough measure, e.g., The core compounds at the heart of OLED displays are often made with expensive substances such as iridium, a rare metal that sells for nearly $19 per gram., certainly complete comparison is more meaningful)
Higher quantum efficiency is an advantage. But, does it worth the price difference? Could lower quantum efficiency of Alq3 be compensated by higher energy consumption? Or Ir-based system is in exploration phase, so to speak.
And actually which one or something else is used in the OLED monitor currently in phone/monitor/TV?