Fine platinum (Pt) particles were deposited electrochemically on n-type silicon (n-Si) electrodes from an aqueous hexachloroplatinic acid(IV) solution by the single potential step (SPS) and double potential step (DPS) methods. The distribution density of the Pt particles on n-Si was 10(8) cm(-2) for the SPS method, whereas it increased from 10(9) to loll cm(-2) by a shift of the pulse potential at the initial step of the DPS method from -1.0 to -4.0 V versus SCE and remained nearly constant at more negative potentials. The size of the Pt particles enlarged with the charge density passing across the electrode surface at a potential of -0.70 V versus SCE, which was applied throughout for the SPS method and at the second step for the DPS method. Photoelectrochemical (PEC) solar cells equipped with Pt-electrodeposited n-Si electrodes generated open-circuit photovoltages (V-OC) of 0.51-0.61 V, much higher than those for n-Si electrodes coated with continuous Pt layers (ca. 0.2-0.3 V). Solar cell characteristics changed with the pulsed potential and charge density passing across the electrode surface which changed the size and distribution density of the Pt particles. The characteristics were explained well by our previous theory on metal-dot coated n-Si electrodes.