Improved performance in dye-sensitized solar cells by rationally tailoring anodic TiO2 nanotube length

► The TNT arrays grow up to 97 μm at an unpredicted speed of 28 μm/h. ► The lengths of TNT arrays are precisely tailored from 10 to 100 μm. ► The DSSC achieves a highest PCE of 4.25% at a nanotube length of 34 μm. ► The TNT arrays show higher electron collection efficiency than nanoparticles.