The measured photocurrent decreases in the order CTF-02 > CTF-02-Bpy 0.66 > CTF-02-Bpy ≈ CTF-02-Bpy 0.33 . Although the introduction of both donor and acceptor moieties in the CTF improves charge generation, it reduces charge separation and charge transport. It has been suggested that all-carbon aromatic moieties (here biphenyl) facilitate charge separation and transfer in comparison to heteroatom-containing aromatic moieties. This could explain the observed highest charge transport in CTF-02, but does not explain the non-monotonous order within the series of bipyridine-containing materials (CTF-02-Bpy 0.66 > CTF-02-Bpy ≈ CTF-02-Bpy 0.33 ). Here, other factors must be at play to counteract the advantage of biphenyl moieties for charge separation and charge transfer. Especially the distance and the time it takes for a charge carrier to diffuse to the particle-substrate-interface, has a significant influence on the charge recombination probability. For example, a high specific surface area, porosity and wettability of the surface should shorten the average diffusion length to the interface. Since CTF-02-Bpy 0.66 shows a greater photocurrent than CTF-02-Bpy 0.33 , while displaying comparable apparent surface area and similar particle sizes (below 200 nm, Figure ), the increased photocurrent of CTF-02-Bpy 0.66 suggests that in this case, the positive effect of higher hydrophilicity overcomes the detrimental effect of lower biphenyl content in the overall photocurrent production. The drop of photocurrent observed when further increasing the bpy content (viz. increased photocurrent of CTF-02-Bpy 0.66 with respect to CTF-02-Bpy) is in line with the beneficial hydrophilicity effect, which is larger for CTF-02-Bpy 0.66 than for CTF-02-Bpy; in this case, though, the adverse effect of lower biphenyl content and/or lower surface area could also concur to this drop in photocurrent (see Table ).