Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV18)
DOI: https://doi.org/10.29363/nanoge.hopv.2018.068
Publication date: 21st February 2018
Metal halide perovskites are mixed ionic-electronic conductors extremely efficient for making solar cells, due to its strong absorption in the visible and their relatively slow recombination. Processes like transport, recombination, charge accumulation, hysteresis, etc. occur at very different time scales and determine the photovoltaic performance of the solar cell. Small-perturbation, frequency-modulated optoelectronic techniques such as impedance spectroscopy (IS) or intensity-modulated photocurrent spectroscopies (IMPS/IMVS) are especially suited to detect, deconvolute and quantify all these processes.
In this talk we discuss a couple of examples where these techniques are used to investigate perovskite solar cells:
(1) By measuring the impedance and the open-circuit photopotential at two excitation wavelengths (blue and red light), in two illumination directions (back and front), and at different temperatures we gain insight on the locus and nature of recombination in TiO2 mesoporous-based perovskite solar cells. With this objective we study different perovskite compositions, i.e., pure MAPbI3 and CsPbI3, as well as mixed ion-based (FAPbI3)0.85(MABr3)0.15, and two different hole selective layers (Spiro-OMeTAD and P3HT)
(2) We again use monochromatic excitations in IS and IMPS to establish how moisture-induced degradation introduce inhomogeneities in the recombination loss at the active layer, hindered transport and charge accumulation at the interfaces.
A simple model is proposed to rationalize the small-perturbation response of the device and its impact on efficiency-determining dynamic processes.