Electron transfer with TD-Split, a linear response time-dependent method

We present a simple method, time-dependent split (TD-Split) for A → B electron transfer by a TD evaluation of the lowest excitation energy from the ground state of the combined (AB)⁻ system. As an example, we study transfer between substituted fullerenes, primarily PCBM. Electron transfer in such fullerene systems is important as it is often the bottleneck in organic solar cells. The TD-Split method is described in detail, including numerical linearization which reduces the number of required iterations, and comparison to other possible approaches. We also compare to other molecules such as C₆₀Me₅H, and find similar trends as experiment.