Charge transfer in photorechargeable composite films of TiO sub(2) and polyaniline

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 sub(2) and a TiO sub(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 sub(2) and PANi, the photorechargeable quantum efficiency QE([electron count on discharge]/[incident photon count on photocharge]) was measured by varying the thickness L sub(S)of the TiO sub(2)-PANi mixture. The quantum efficiency QE sub(uv) for UV photons had a maximum of ~7% at L sub(S) 7 mu m. The time constant [tau] sub(TP) for the charge transfer was about 10 super(-1) s, which was longer ten times or more than the lifetime of excited electrons within TiO sub(2). These facts reveal that the main rate-limiting factor in the photocharging process is the charge transfer between TiO sub(2) and PANi.