Perovskite Solar Cells (PSCs) have emerged as a very promising alternative in comparison to silicon based solar cells due to the combination of high light absorption coefficients and outstanding solar energy conversion efficiencies of more than 20% with simple and cheap methods of fabrication like spin coating or other fluid-to-solid transformation processes [1,2].

The dynamic response of photo voltage (IMVS) and photocurrent (IMCS) on light, modulated with changing frequencies, is generally addressed as Intensity Modulated Photo Spectroscopy (IMPS) [3,4,5]. It is a linear, small signal method close to Electrochemical Impedance Spectroscopy (EIS). IMPS is a technique popular for instance in the fields of Dye Sensitized Solar Cells (DSSC) when evaluating the competition between photo charge carrier lifetime and diffusion speed. IMPS intentionally uses bias light superimposed with a small modulation in order to maintain linearity [3,4,5]. On the contrary, intensity transients leave linearity. This is due to the large perturbation induced by switching light from the on-state to the off-state, or vice versa.  A couple of characteristic properties are assumed to be in steady state in the case of IMPS, but they are changing dramatically under light transients. The latter technique is offering the possibility of getting additional insights into ultrafast processes. It is therefore advantageous, when linear dynamic measurements under frequency variation, like IMPS and IMVS, can be put in relation to measurements of transient behaviour in the time domain. In the present work IMPS data of an Organic Solar Cell (OSC) sample were recorded at specific bias intensities. The spectra were interpreted by means of AC modelling and fitting. For comparison, the same samples were characterized by means of fast intensity transients, again. Therefore, the intensity was switched off within 80 ns, with and without keeping the background intensity at a certain bias. The results were compared with the IMPS results and the contribution of the photoconductivity could be identified.

1    N.-G. Park, J. Phys. Chem. Lett., 2013, 4, 2423–2429.

2    G. Niu, X. Guo and L. Wang, J. Mater. Chem. A, 2015, 3, 8970–8980.

3    E. A. Ponomarev and L. M. Peter, J. Electroanal. Chem., 1995, 396, 219–226.

4    Y. Zhao, A. M. Nardes and K. Zhu, Faraday Discuss., 2014, 176, 301–312.

5    G. O. Kim and K. S. Ryu, Bull. Korean Chem. Soc., 2012, 33, 469–472.