It is important to note here that c † scales very differently with N compared with the overlap volume fraction φ * , which has been used previously to predict aggregation properties. The work of ref. 17, which considered a single polymer (DPP-DTT, which is significantly different chemically to P(NDI2OD-T2)) at concentrations close to the overlap concentration, suggested that the optimal concentration for achieving high-performing organic fieldeffect transistor (OFET) devices is the polymer overlap concentration. If this is the case, the optimal concentration is expected to decrease with N, and c † should be roughly constant for constant φ V N 1/2 (approximating φ * ∼ φ V N 1/2 ). Fig. shows that this is not the case for the simulations in this work, with the value of φ V N 1/2 at which τ s = τ c scaling roughly linearly with N.