  Sustainable efficient light emitter based solely on elements-of-hope are
needed to replace current compounds based on less-abundant materials.
Functionalized diamondoids are a potential solution for this challenge as they
offer efficient, octave-spanning emission across the visible spectrum in their
single-crystalline form. Its large quantum efficiency increases towards
higher-than-ambient temperatures to beyond 7 %. The stability beyond 200
{\deg}C renders such functionalized diamondoids as sustainable phosphors for
LED applications. Detailed structural and theoretical investigations suggest a
crucial role of exciton states accompanied by structural modifications
(self-trapped excitons) in the emission process.
