As stated in the article, you need to have all three spectra. Then normalize them, i.e. integrate each and equal that to 1. Then apply the new values for P, E and R into the integrals in the equation for QE. Hope this helps.

collect UV and PL spectra of the fluorescent material, make calibration plot of both.

Rahul Rade is Okay

The Internal quantum yield (iQY) is a ratio between the number of emitted photons from a sample (Es) and the photons absorbed by the same sample (As). Where As is the difference between reflectance from a standard white material (Rstd) (i.e. Spectralon, Barium sulfite, etc.) and reflectance from the studied material (Rs), or be As = (Rstd – Rs). Due to this, iQY = Es/(Rstd - Rs),

and

the External quantum yield (EQY) is the ratio between the number of emitted photons from the sample (Es) and the photons input onto the sample (Rstd) (It includes all photons coming in the sample, Absorbed and Reflected): EQY = Es/(Rstd)

Both (IQY and EQY) is obtained by an integrating sphere.

On the other hand, Quantum Efficiency (QE) is related to a single electronic level, and it is the ratio between the experimental lifetime and calculated lifetime determined by a theoretical method.

A simple method to calculate this using Reflectance spectra is provided in this paper: M.S. Wrighton, D.S. Ginley, D.L. Morse, A technique for the determination of absolute emission quantum yields of powdered samples, The Journal of Physical Chemistry, 1974, 78 (22), 2229.

You could also check the Supplementary Information of our paper ( New J. Chem., 2019, 43, 17446-17456 ) (Measured from PL spectra) on how both iQY and EQY were measured.