in which N corresponds to the Avogadro's number, k 2 is the orientation factor regarding the transition vectors of the donor PL and acceptor absorption, 𝜙 𝑓 is the PLQY of the donor in the absence of acceptor, n is the refractive index of the medium, FD(λ) is the normalized fluorescence spectrum of the donor, εR(λ) is the molar absorption coefficient of the acceptor Equation 1