, resulting in a two-fold reduction of the rate due to the light-matter hybridization. However, more significant modifications can come from the exponential part of Eq. 168, which depends on ∆G ± c . When considering a wide range of light-matter coupling strengths ℏg c , the PMET driving force ∆G ± c and thus the PMET rate (Eq. 168) can be tuned significantly. Note that Eq. 168 is based on the JC model, which is simple and intuitive but will eventually breakdown (see Fig. ) when g c /ω c ≥ 0.1. Directly numerical calculations of ∆G ± c and V ± c are necessary when going beyond the JC approximation, which is detailed in Ref. 12. Fig. demonstrates the upper and lower polariton surfaces and their energetic shifts for several different Rabi splittings. Comparing these polariton surfaces to the acceptor surface |A, 0⟩ in solid black, the polariton surfaces are able to access many different charge transfer regimes (normal, activation-less, and inverted), where the forward ET reaction can be made more or less favorable depending on the initial state (upper or lower polariton) and the magnitude of the Rabi splitting. This can be seen in the effect of different light-matter coupling strengths g c on the PMET rate as predicted from Marcus theory. The cavity-induced Rabi splitting raises the energy of the upper polariton surface and lowers the energy of the lower polariton surface (Fig. ). Consequentially, the ∆G from the upper polariton to the acceptor will decrease while the ∆G from the lower polariton to the acceptor will increase. In particular, if the acceptor state has higher energy than the bare donor state, but lower energy than the upper polariton state, an uphill reaction outside the cavity can be modified as a downhill reaction inside the cavity, when exciting to the upper polariton surface (and when the upper polariton lifetime is long enough for the reaction, e.g., under a continuous irradiation condition that constantly supplies |UP⟩ population. Fig. presents the PMET rates from the upper polariton |+⟩ to the acceptor |A, 0⟩ as a function of ℏg c , predicted from Marcus theory (solid line) and from a partial-linearized density matrix (PLDM) dynamics simulation 284 (dotted line). The PMET rate can be enhanced by a factor of over 100 for this model when the system is resonantly coupled to an optical cavity with a coupling strength of ℏg c = 600 meV. Beyond this coupling strength, the rate begins to decrease due to the |+⟩ state sitting in the Marcus inverted regime. Alternatively, the lower polariton could be initially excited to more readily sample other Marcus regimes resulting in a PMET rate smaller than those outside the cavity. For systems with donor states that have non-zero reorganization energy relative to the ground state, the donor excited state |D⟩ and the ground state |G⟩ are modeled as parabolas with different minima positions, as illustrated in Fig. . In the limit that the Rabi splitting is larger than the donor-ground reorganization energy and the light-matter detuning, the polariton states |±⟩ (generated by hybridizing the |D, 0⟩ and |G, 1⟩ states) are nearly harmonic and have a potential minimum that is in between the minima of the |D⟩ and |G surfaces, as illustrated in Fig. . This results in an effective reduction of the reorganization between the polariton states and the ground state. This effective reorganization energy is reduced by a factor of 1/4 relative to the original donor-ground reorganization energy outside the cavity due to the polariton superposition only having half of the donor character. Note that the PMET rate is exponentially sensitive to the effective reorganization energy (Eq. 168). This mechanism of enhancing PMET due to the effective reduction of the ET reorganization energy is referred to as the polaron decoupling mechanism. Note that this effect only changes the donor-ground reorganization energy and does not affect the acceptor-ground reorganization energy for acceptor states that do not couple to the cavity.