Singlet Excitons: High Yields of Singlet Excitons in Organic Electroluminescence through Two Paths of Cold and Hot Excitons (Advanced Optical Materials 6/2014)

The initial ratio between the singlet (pink balls) and triplet (blue balls) excitons should be 1:3 according to spin statistics. On page 510, B. Yang, Y. Ma, and co‐workers describe how a very small singlet–triplet energy split between S 2 and T 2 with a dominant charge‐transfer character and a large energy gap between T 1 and T 2 could cause reverse intersystem crossing along the ‘hot exciton’ charge‐transfer state channel of T 2 →S 2 , resulting in a high singlet exciton ratio of >25%.