The impact of internal interfaces in perovskite solar cells on photocharges

Session

Nanoscale Science of Materials for Energy Storage and Generation

Authors

Dr Ilka Hermes (2), Prof Stefan Weber (3), Dr Liam Collins (5), Prof Yo Hou (4), Prof Christoph Brabec (1)

Affiliations

1. Friedrich-Alexander-Universität
2. Leibniz Institute of Polymer Research
3. Max Planck Institute for Polymer Research
4. National University of Singapore
5. Oak Ridge National Laboratory

Keywords

Kelvin probe, piezoresponse, perovskite solar cells, Ferroelastic

Abstract text

Perovskite solar cells that are based on the prototype mixed organic-inorganic perovskite material methylammonium lead iodide (MAPbI₃) feature various internal interfaces on different length scales: From heterointerfaces to the charge extraction layers over grain boundaries within the multicrystalline MAPbI₃ absorber layer, down to twin domain boundaries within individual MAPbI₃ grains. We investigated the influence of these interfaces on the transport of photo-generated charge carriers via a combination of electrical and electromechanical AFM techniques and correlated this nanoscale information to macroscopic current-voltage detection and time-resolved photoluminescence measurements. 

The photopotential distribution of solar cell crosssections, resolved via heterodyne Kelvin probe force microscopy, revealed that the chamical instability of the heterointerface to the organic hole extraction material SpiroMeOTAD introduces a barrier to the photocharge transport and thereby increases the series resistance of the solar cell [1]. On a smaller length scale, we observed that even subcrystalline twin domain boundaries in individual MAPbI₃ grains affect the photocharge dynamics by correlating an extensive piezoresponse force microscopy study to time- and spatially resolved photoluminescence measurements. We found that domain walls delay the perpendicular charge carrier diffusion compared to the charge diffusion parallel to the domain walls [2, 3]. 

Both studies illustrate how the local functional information that is accessible by the AFM can visualize and elucidate structural impedements in applied energy divices - valuable information for future performance improvements.

References

[1] IM Hermes, Y Hou, VW Bergmann, CJ Brabec, SAL Weber, The Journal of Physical Chemistry Letters 2018, 9 (21), 6249-6256

[2] IM Hermes, SA Bretschneider, VW Bergmann, D Li, A Klasen, J Mars, et al., The Journal of Physical Chemistry C 2016 120 (10), 5724-5731

[3] IM Hermes, A Best, L Winkelmann, J Mars, SM Vorpahl, M Mezger, et al., Energy & Environmental Science 2020 13 (11), 4168-4177