Delayed fluorescence spectrum completely overlaps with the prompt fluorescence spectrum with the only difference of their lifetime (Longer than fluorescence but shorter than phosphorescence). It is of two type: E-type (Eosin type also called Thermally activated) and P-type (Pyrene type also called triplet triplet annihilation). P-type delayed fuorescence intensity has a characteristic quadratic dependence with excitation light intensity while E type shows linear dependence. P type delayed fuorescence is a collisional energy transfer process while E -type delayed fuorescence is not an energy transfer process but occurs due to smaller energy gap between singlet and triplet state which results in reverse intersystem crossing of electron from triplet to singlet state due to thermal activation.

If you type your question in google a lot of good answers. I found three to start

https://answers.yahoo.com/question/index?qid=20100902081203AA6cV6L

and a nice paper

http://pubs.acs.org/doi/pdf/10.1021/jp0214110

"Delayed fluorescence is a non-collisional energy transfer process. This process

has the fluorescence characteristic emission spectrum but a lifetime only a

bit shorter than phosphorescence" Taken from:

https://physik.unibas.ch/Praktikum/VPII/Fluoreszenz/Fluorescence_and_Phosphorescence.pdf

Google and Scholar are great places to start, tons of info. Hopefully it will help you.

Delayed fluorescence spectrum completely overlaps with the prompt fluorescence spectrum with the only difference of their lifetime (Longer than fluorescence but shorter than phosphorescence). It is of two type: E-type (Eosin type also called Thermally activated) and P-type (Pyrene type also called triplet triplet annihilation). P-type delayed fuorescence intensity has a characteristic quadratic dependence with excitation light intensity while E type shows linear dependence. P type delayed fuorescence is a collisional energy transfer process while E -type delayed fuorescence is not an energy transfer process but occurs due to smaller energy gap between singlet and triplet state which results in reverse intersystem crossing of electron from triplet to singlet state due to thermal activation.

http://old.iupac.org/goldbook/D01579.pdf

https://www.nature.com/articles/213385a0

Difference between Prompt and Delayed Fluorescence Spectra

http://old.iupac.org/goldbook/D01579.pdf

https://www.nature.com/articles/213385a0

Colleagues answered correctly. The maxima of the spectrum of fast and delayed fluorescence coincide, since the radiation occurs from the same zero vibrational level of the first excited state. However, in the excited state due to the singlet-triplet transition and vice versa, the lifetime of delayed fluorescence is several orders of magnitude longer. The maximum of the phosphorescence spectrum will be shifted to the long-wavelength region with respect to any fluorescence, since the radiation comes from the triplet level, whose energy is less. The phosphorescence spectrum also has a large half-width and does not immediately disappear when the exciting light is turned off.