Fig. 2. Angle-resolved reflectivity and Jablonski diagram of the system in the strong coupling regime.

a Angle-resolved reflectivity (transverse electric mode) of a planar HJ cavity. The white solid lines indicate the excitons (Ex_PTCDA1, Ex_PTCDA2, and Ex_DPA1) and the blue line the cavity energy (E_Cav). The three excitons of PTCDA and DPA are strongly coupled to the $\lambda$ mode of the cavity, leading to the formation of four polaritonic modes (LP, MP1, MP2, and UP), indicated by magenta dashed lines, which are a fit to a coupled oscillator model. b Jablonski diagram of the system. In the diagram, the two excitons of PTCDA are represented by a broad S₁ band to simplify the diagram without affecting the underlying physics. The cavity photon ($ħ{\omega }_c$) couples to both PTCDA and DPA and by doing so form the upper (UP), middle (MP), and lower polaritons (LP). The gray-color bands represent dark states. k₀ and k_CT are the decay rates of excited PTCDA to the ground state and charge-transfer state in the absence of a cavity, and k_LP and k_LPtoCT are the corresponding decay rates of LP to the ground state and charge-transfer states, respectively. The double arrow indicates the energy transfer between the exciton reservoir and LP. c Normalized emission spectra (excited at 475 nm) of the planar HJ cavity (Cav_Planar) and the reference cavity (Cav_PTCDA).