Fig. 10: The mechanism of excitonic dissociation.

a Temperature-dependent photoluminescence (TD-PL) of TPC-3D at different temperatures. b The E_ar was calculated by fitting the temperature dependence of PL intensity with the Arrhenius equation. c Illustration of the mutual transitions between the charge separated state (CS) and the lowest singlet excited state (S₁) in PYR-2D, where the value of excitonic binding energy (E_b) is positive and E_a is the activation energy from S₁ to CS. d Illustration of mutual transitions between CS and S₁ in TPC-3D and TPL-2D, in which the value of E_b is negative, and E_ar is the activation energy from CS to S₁. This indicated that the energy barrier for exciton dissociation into free charge was lower than the thermal energy at room temperature, and the energy level of the charge-separated state was even lower than that of the exciton state. In other words, the separation of excitons was spontaneous in TPD-3D and TPL-2D at room temperature. e Calculation of the ionization potential (IP), electron affinity (EA), and Mulliken electronegativity of TPC, PYR, TPL and AQ monomers. Mulliken electronegativity = (IP + EA)/2. The smaller the Mulliken electronegativity, the stronger the electron-giving ability. TPC monomer is more capable of giving electrons than PYR and TPL monomers, while AQ monomer tends to gain electrons. f Electrostatic potential (ESP) of TPC-3D. The uneven charge distribution of the system is a reflection of the molecular polarity, and the more uneven the distribution results in more positive or negative areas of the electrostatic potential on the surface of the molecule (See Supplementary Fig. 60 for more detailed information).