Light-induced performance changes in metal halide perovskite solar cells (PSCs) have been studied intensively over the last decade, but little is known about the variation in microscopic optoelectronic properties of the perovskite heterojunctions in a completed device during operation.*
For the article “Operando Characterizations of Light-Induced Junction Evolution in Perovskite Solar Cells “ Chuanxiao Xiao, Yaxin Zhai, Zhaoning Song, Kang Wang, Changlei Wang, Chun-Sheng Jiang, Matthew C. Beard, Yanfa Yan and Mowafak Al-Jassim combined Kelvin probe force microscopy and transient reflection spectroscopy techniques to spatially resolve the evolution of junction properties during the operation of metal-halide PSCs and study the light-soaking effect.*
Their analysis showed a rise of an electric field at the hole-transport layer side, convoluted with a more reduced interfacial recombination rate at the electron-transport layer side in the PSCs with an n–i–p structure. The junction evolution is attributed to the effects of ion migration and self-poling by built-in voltage. Device performances are correlated with the changes of electrostatic potential distribution and interfacial carrier dynamics. *
The author’s results demonstrate a new route for studying the complex operation mechanism in PSCs. *
NANOSENSORS Platinum-Iridium coated PointProbe® Plus PPP-EFM AFM probes were used for the Kelvin Probe Force Microscopy*
The NANOSENSORS PPP-EFM has two resonant peaks, one low-frequency peak (∼50 kHz) was used for topography, and the other higher frequency peak (∼350 kHz) was used for electrostatic force measurements. *
Topography and potential images were acquired at the same time, where the spatial resolution is 30 nm and the electrical resolution is 10 mV. The cell was cleaved directly without polishing or ion milling, but the cross-sectional surface is flat enough for KPFM scans. *
Chuanxiao Xiao et al applied forward and reverse bias voltages alternatively to minimize the ion migration effect. The scan on each bias voltage condition contains 1024 pixels in the fast-scan axis across the cell, and 32 lines in the slow-scan axis on the film direction, with a scan rate of 0.35 Hz that takes ∼90 s per scan. The scans were on the same location, judging by their topography. The cell was illuminated by a halide lamp at its maximum power, the light intensity is ∼0.5 Sun coming through the glass side. The forward and reverse bias voltages stressing utilized the KPFM setup. All sample preparation, light soaking, dark rest, biasing, and measurements were performed inside an Ar-filled glovebox with oxygen and water level <0.01 ppm. *
Figure 1 from “Operando Characterizations of Light-Induced Junction Evolution in Perovskite Solar Cells” by Chuanxiao Xiao et al.
Experiment schematic. KPFM scans on the cleaved cross-sectional surface. Ultrafast spectroscopy measurements were in both TA and TR setups.
*Chuanxiao Xiao, Yaxin Zhai, Zhaoning Song, Kang Wang, Changlei Wang, Chun-Sheng Jiang, Matthew C. Beard, Yanfa Yan and Mowafak Al-Jassim
Operando Characterizations of Light-Induced Junction Evolution in Perovskite Solar Cells
ACS Applied Materials & Interfaces 2023, 15, 17, 20909–20916
DOI: https://doi.org/10.1021/acsami.2c22801
Open Access: The article “Operando Characterizations of Light-Induced Junction Evolution in Perovskite Solar Cells” by Chuanxiao Xiao, Yaxin Zhai, Zhaoning Song, Kang Wang, Changlei Wang, Chun-Sheng Jiang, Matthew C. Beard, Yanfa Yan and Mowafak Al-Jassim is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/.