Apart from broadband absorption of solar radiation, the performance of photovoltaic devices is governed by the density and mobility of photogenerated charge carriers. The latter parameters indicate how many free carriers move away from their origin, and how fast, before loss mechanisms such as carrier recombination occur. However, only lower bounds of these parameters are usually obtained. Here we independently determine both density and mobility of charge carriers in a perovskite film by the use of time-resolved terahertz spectroscopy. Our data reveal the modification of the free carrier response by strong backscattering expected from these heavily disordered perovskite films. The results for different phases and different temperatures show a change of kinetics from two-body recombination at room temperature to three-body recombination at low temperatures. Our results suggest that perovskite-based solar cells can perform well even at low temperatures as long as the three-body recombination has not become predominant.

The use of a fast temperature jump (T-jump) is a very powerful experiment aiming at studying protein denaturation dynamics. However, probing the secondary structure is a difficult challenge and rarely yields quantitative values. We present the technical implementation of far-UV circular dichroism in a nanosecond T-jump experiment and show that this experiment allows us to follow quantitatively the change in the helical fraction of a poly(glutamic acid) peptide during its thermal denaturation with 12 ns time resolution.

This article contains errors in the units used for carrier mobility. In Fig. 2a-d, the units on the y axis should be 'cm 2 V À 1 s À 1 ' not 'V À 1 s À 1 cm À 1 '. Similarly, the second and third sentences of the second paragraph of the 'Quantum yield calculation' section should read 'From Fig. 2 and Table 1, we obtain fm(1 þ c 1 ) ¼ 11 cm 2 V À 1 s À 1 and fk 2 ¼ 11 Â 10 À 10 cm 3 s À 1 . These data compare well with the corresponding values of 8.2 cm 2 V À 1 s À 1 and 9.2 Â 10 À 10 cm 3 s À 1 in Wehrenfennig et al. 8 where the support was mesoporous alumina.'

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