where V DA = ⟨D| Ĥel |A⟩ is the donor-acceptor coupling strength, β = 1/k B T with Boltzmann constant k B and temperature T , λ ET is the reorganization energy associated with the electron transfer reaction (not to be confused by the light-matter coupling strength in Eq. 105), and ∆G is the difference in free energy between the donor and acceptor states (also known as the driving force). When including the ground state in this description, the ground, donor, and acceptor states can be thought of as parabolas that are shifted from each other in terms of their minimum energy and nuclear configuration, with coupling between the donor and acceptor parabolas. When a charge transfer reaction is coupled to an optical cavity, many of the key parameters in Eq. 167 are modified due to light-matter coupling. One of the most important modifications is to the driving force ∆G as shown in Fig. , adapted from Ref. 12. In this model, three diabatic electronic states are considered: a ground state |G⟩, an optically bright excited state denoted as the donor state |D⟩, and an optically dark excited state, denoted as the acceptor state |A⟩. This model setup could correspond to many experimental systems such as a colloidal nanocrystal (NC) as a donor molecule and an organic acceptor molecule. The molecular excitation transition |G⟩ → |D⟩ is coupled to the cavity (due to its non-zero ground-to-excited transition dipole moment) whereas the acceptor state |A⟩ (which is also an electronic excited state) is not directly coupled to the cavity but is coupled to the donor state |D⟩ through the diabatic electronic coupling V DA . It is also assumed that the donor excited state |D⟩ and the ground state |G⟩ have the same minima position, meaning there is no Huang-Rhys factor (or reorganization energy) between |D⟩ and |G⟩. This means that the |G, 1⟩ state (orange solid curve in Fig. ) and the |D, 0⟩ state (black dashed curve in Fig. ) are nested with the same minimum position, indicating the ET re-organization energy λ is not changed upon coupling to the cavity (as opposed to the case illustrated in Fig. ).