A photorechargeable battery (PRB) is a photovoltaic device having an energy storage function in a single cell. The photoactive electrode of PRB is a bilayer film consisting of bare porous TiO 2 and a TiO 2 -polyaniline (PANi) mixture that work as a photovoltaic current generator and an electrochemical energy storage by ion dedoping, respectively. To study the charge transfer between TiO 2 and PANi, the photorechargeable quantum efficiency QE ([electron count on discharge]/[incident photon count on photocharge]) was measured by varying the thickness L S of the TiO 2 -PANi mixture. The quantum efficiency QE uv for UV photons had a maximum of >7% at L S > 7 µm. The time constant τ TP for the charge transfer was about 10 %1 s, which was longer ten times or more than the lifetime of excited electrons within TiO 2 . These facts reveal that the main rate-limiting factor in the photocharging process is the charge transfer between TiO 2 and PANi.