Invited Paper NS+AM+MI+MN+SS+TR-TuA7
Advances in SPM Methods for Energy-relevant Materials

Tuesday, October 23, 2018, 4:20 pm, Room 102B

The scientific understanding of nanoscale materials and devices is continuously growing ever since atomic force microscopy (AFM) has enabled us to image these systems at similar length scale. Specifically, there is a pressing need for functional imaging as energy-relevant technologies are becoming dominated by nano- and mesoscale constructs. In this presentation I will review my group’s recent research discoveries based on new AFM methods to measure and determine how the electrical, chemical, and/or optical properties influence overall photovoltaic device behavior [1,2]. We realize novel functional imaging AFM-based methods to elucidate the driving forces for the dynamic response of the perovskites upon and post-illumination [3], and polycrystalline materials for solar cells [4,5]. We map nanoscale variations in open-circuit voltage Voc > 300 mV under 1-sun illumination, not revealed by conventional AFM tools. Using fast-KPFM (16 seconds/scan) while maintaining high spatial sensitivity, we map, in real-time, the dynamics of the Voc in perovskite solar cells with spatial resolution < 100 nm. Unexpectedly, we identify a ‘residual Voc’ post-illumination, attributed here to iodine ion migration, a process that takes place in a time scale of several minutes. We foresee our functional imaging tool to be implemented in the identification of stable perovskite compounds, ranging from lead-free and non-toxic alternatives to new options for tandem designs.

[1] ACS Energy Letters 2, 2761 (2017). Invited Review.

[2]ACS Energy Letters 2, 1825 (2017). Invited Perspective

[4] ACS Energy Letters1, 899 (2016).

[5] Advanced Energy Materials 5, 1501142 (2015).