Jacques Moser and co-workers: Photoinduced charge transfer processes in solar cells

January 19, 2014

Unravelling the mechanism of photoinduced charge transfer processes in lead iodide perovskite solar cells

Lead halide perovskites have recently been used as light absorbers in hybrid organic–inorganic solid-state solar cells, with efficiencies as high as 15% and open-circuit voltages of 1 V. However, a detailed explanation of the mechanisms of operation within this photovoltaic system is still lacking. Here, we investigate the photoinduced charge transfer processes at the surface of the perovskite using time-resolved techniques. Transient laser spectroscopy and microwave photoconductivity measurements were applied to TiO₂ and Al₂O₃ mesoporous films impregnated with CH₃NH₃PbI₃ perovskite and the organic hole-transporting material spiro-OMeTAD. We show that primary charge separation occurs at both junctions, with TiO₂ and the hole-transporting material, simultaneously, with ultrafast electron and hole injection taking place from the photoexcited perovskite over similar timescales. Charge recombination is shown to be significantly slower on TiO₂ than on Al₂O₃ films.

Marchioro, A., Teuscher, J., Friedrich, D., Kunst, M., van de Krol, R., Moehl, T., Grätzel, M.l., and Moser, J.-E. (2014) Unravelling the mechanism of photoinduced charge transfer processes in lead iodide perovskite solar cells. Nat. Photon. 8, 250-255, (10.1038/nphoton.2013.374).

The paper was discussed on a series of websites:

• EurekAlert!  “Understanding the functioning of a new type of solar cell”
• Phys.org “Scientists unravel the mechanism of the functioning of a new type of solar cell”
• Science Daily “Understanding the functioning of a new type of solar cell”
• R&D “Understanding perovskite-based solar cells”
• The Engineer “Insight into perovskites increases solar cell potential”
• pro-physik.de “Kurzer Prozess”
• Science World Report “Understanding the function of a new type of solar cell”
• EPFL “Le fonctionnement d'un nouveau type de cellules solaires élucidé”
• EPFL “Understanding the function of a new type of solar cell”
• EPFL “Towards a new type of solar cell”
• Goodnight Earth “New solar cell architecture provides efficiency competitive with thin film photovoltaics”
• DailyFusion “Scientists uncover charge transfer mechanism in perovskite solar cells”
• Press-News.org “Understanding the functioning of a new type of solar cell”
• Enerzine.com “Le fonctionnement d'un nouveau type de cellules solaires élucidé”

Figure 1: Schematic diagram of energy levels and electron transfer processes in an HTM|perovskite|TiO2 cell.


Figure 2: Time evolution of electron and hole populations in photoexcited CH3NH3PbI3 perovskite in various systems.


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