We report data for a pair of singlestack all-phosphorescent organic light emitting-diode (OLED) light panels with high efficacy, long lifetime, and very low operating temperature: Panel 1 has efficacy, and lifetime to at , while Panel 2 has efficacy, and lifetime to at . Operating at a higher luminance of , Panel 2 has efficacy with lifetime to . Excellent panel lifetime is enabled by a stable light blue phosphorescent materials system. Panel temperatures are within 10°C of ambient temperature at . Panel 2 was further used as a building block to demonstrate an all-phosphorescent OLED luminaire for under-cabinet lighting applications. Operating at approximately , the luminaire delivers 570 lm with total system efficacy, and .