Multiple Exciton Collection in a Sensitized Photovoltaic System

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Abstract
Two for One: Solar cells often contain materials that absorb a broad spectrum of light above a certain frequency threshold, or band gap. Unfortunately, much of the energy contained in this light is wasted, because any balance exceeding the band gap tends to be dissipated as heat, rather than harnessed into electric current. Recent spectroscopic studies have shown that incident photons with energy several multiples of the band gap can transiently generate more than one current carrier, but the excess carriers tend to collapse before they can be diverted into the circuit. Sambur et al. (p. 63 ) now show that, when light-absorbing lead sulfide nanoparticles are carefully coupled to smoothly polished titanium dioxide crystalline electrodes, such excess carriers can be transferred into the circuit before collapsing.