where me is the mass of electron, ∆E is the energy of transition, ℏ is the reduced Planck's constant, and e is the charge of electron. As excepted, CCO-1 has a larger µ than CBP-1, which brings about a larger f value, and the TDM direction of CCO-1 dominantly aligns along the x-y plane (Fig. and Supplementary Table ). During evaporation, CCO-1 has a higher tendency to align horizontally on substrate with a larger Θ// than CBP-1. These findings also validate the presence of planar polycyclic CCO-α has positive effect to promote horizontal transition dipole orientation. Moreover, according to Einstein's spontaneous emission equation (2) :