Publications associated with Photovoltaic and Optoelectronic Device Group

Photon recycling in lead iodide perovskite solar cells.

Science (New York, N.Y.) 351 (2016) 1430-1433

LM Pazos-Outón, M Szumilo, R Lamboll, JM Richter, M Crespo-Quesada, M Abdi-Jalebi, HJ Beeson, M Vrućinić, M Alsari, HJ Snaith, B Ehrler, RH Friend, F Deschler

Lead-halide perovskites have emerged as high-performance photovoltaic materials. We mapped the propagation of photogenerated luminescence and charges from a local photoexcitation spot in thin films of lead tri-iodide perovskites. We observed light emission at distances of ≥50 micrometers and found that the peak of the internal photon spectrum red-shifts from 765 to ≥800 nanometers. We used a lateral-contact solar cell with selective electron- and hole-collecting contacts and observed that charge extraction for photoexcitation >50 micrometers away from the contacts arose from repeated recycling between photons and electron-hole pairs. Thus, energy transport is not limited by diffusive charge transport but can occur over long distances through multiple absorption-diffusion-emission events. This process creates high excitation densities within the perovskite layer and allows high open-circuit voltages.

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