Enhanced self-assembled monolayer surface coverage by ALD NiO for p-i-n perovskite solar cells

Nga Phung^a, Marcel Verheijen^a, Anna Todinova^a, Kunal Datta^a, Amran Al-Ashouri^b, Michael Verhage^c, Xin Li^b, Antonio Abate^b, Steve Albrecht^b, Mariadriana Creatore^a

^aEindhoven University of Technology, Department of Applied Physics, 5600MB, Eindhoven, Netherlands

^bHelmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany, Berlin, Germany

^cDepartment of Chemical Engineering and Chemistry, Eindhoven University of Technology (TU/e), P.O. Box 513, Eindhoven, 5600 MB, Netherlands

International Conference on Hybrid and Organic Photovoltaics
Proceedings of 13th Conference on Hybrid and Organic Photovoltaics (HOPV21)

Online, Spain, 2021 May 24th - 28th

Organizers: Marina Freitag, Feng Gao and Sam Stranks

Oral, Nga Phung, presentation 091
Publication date: 11th May 2021

Halide perovskites have attracted tremendous attention due to their excellent opto-electronic properties. This has enabled perovskite PV single junction to reach record efficiencies of 25.5%[1]. The progress of perovskite in PV applications is the result of the improvement of the opto-electrical properties of the perovskite absorber, as well as of the quality of the interface between transport layers and the perovskite absorber. Specifically, the recent introduction of self-assembled monolayers (SAMs) as charge transport layers on ITO has led to highly efficient devices[2-3], as well as a recent tandem perovskite/Si record of 29.5%[4]. Thus, SAM-based transport layers are expected to be part of the technological roadmap of perovskite PV.

So far, limited investigation has been carried out on the surface coverage of SAMs on ITO. Surface coverage is important because non-covered areas can result in low open circuit voltage and electrical shunts, thus reducing the device efficiency. To date, it has been shown that the SAM quality depends on the ITO crystallinity and morphology, as well as its surface treatment prior to SAMs processing[5-6]. In this study, we investigate the surface coverage of SAM on ITO using MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid) employed in a p-i-n structure of ITO/SAM/CsFAMA/C₆₀/BCP/Cu by transmission electron microscopy (TEM) in combination with conductive atomic force microscopy (c-AFM) mapping. We observe that processing SAM directly on ITO can result in an inhomogeneous layer, with areas having low molecular density in TEM images. Supporting the TEM images analysis, c-AFM map also reveals exposed ITO areas due to insufficient SAM coverage in ITO+SAM sample. We attribute this inhomogeneity to large device performance spread seen in ITO+SAM devices. On the other hand, when adopting an atomic layer deposited NiO[7-8] between ITO and MeO-2PACz, the homogeneity, and thus, the surface coverage of the SAM improve. The cross-sectional TEM images of NiO+SAM device point out to a homogeneous SAM layer on NiO in contrast to direct growth on ITO. The homogeneous distribution of SAM molecules on NiO and the low lateral conductivity of NiO lead to narrower device efficiency distribution with high shunt resistance on average reaching more than 20% efficiency with NiO+SAM device. Notably, NiO layers do not require pre-treatment prior to the SAM solution process, which offers an advantage over ITO - eliminating the discrepancy in ITO pre-treatment and properties. We trust that this finding can further promote the benefit of using phosphonic acid-based molecules as contact layers in PSCs.

References:

[1] Green, M.A., Dunlop, E.D., Hohl‐Ebinger, J., Yoshita, M., Kopidakis, N. and Ho‐Baillie, A.W., 2020. Solar cell efficiency tables (Version 55). Progress in Photovoltaics: Research and Applications, 28(1), pp.3-15.

[2] Al-Ashouri, A., Magomedov, A., Roß, M., Jošt, M., Talaikis, M., Chistiakova, G., Bertram, T., Márquez, J.A., Köhnen, E., Kasparavičius, E. and Levcenco, S., 2019. Conformal monolayer contacts with lossless interfaces for perovskite single junction and monolithic tandem solar cells. Energy & Environmental Science, 12(11), pp.3356-3369.

[3] Yalcin, E., Can, M., Rodriguez-Seco, C., Aktas, E., Pudi, R., Cambarau, W., Demic, S. and Palomares, E., 2019. Semiconductor self-assembled monolayers as selective contacts for efficient PiN perovskite solar cells. Energy & Environmental Science, 12(1), pp.230-237.

[4] Al-Ashouri, A., Köhnen, E., Li, B., Magomedov, A., Hempel, H., Caprioglio, P., Márquez, J.A., Vilches, A.B.M., Kasparavicius, E., Smith, J.A. and Phung, N., 2020. Monolithic perovskite/silicon tandem solar cell with> 29% efficiency by enhanced hole extraction. Science, 370(6522), pp.1300-1309.

[5] Chockalingam, M., Darwish, N., Le Saux, G. and Gooding, J.J., 2011. Importance of the indium tin oxide substrate on the quality of self-assembled monolayers formed from organophosphonic acids. Langmuir, 27(6), pp.2545-2552.

[6] Hubmann, A.H., Dietz, D., Brötz, J. and Klein, A., 2019. Interface Behaviour and Work Function Modification of Self-Assembled Monolayers on Sn-Doped In2O3. Surfaces, 2(2), pp.241-256.

[7] Koushik, D., Jošt, M., Dučinskas, A., Burgess, C., Zardetto, V., Weijtens, C., Verheijen, M.A., Kessels, W.M., Albrecht, S. and Creatore, M., 2019. Plasma-assisted atomic layer deposition of nickel oxide as hole transport layer for hybrid perovskite solar cells. Journal of Materials Chemistry C, 7(40), pp.12532-12543.

[8] Jošt, M., Bertram, T., Koushik, D., Marquez, J.A., Verheijen, M.A., Heinemann, M.D., Köhnen, E., Al-Ashouri, A., Braunger, S., Lang, F. and Rech, B., 2019. 21.6%-efficient monolithic perovskite/Cu (In, Ga) Se2 tandem solar cells with thin conformal hole transport layers for integration on rough bottom cell surfaces. ACS Energy Letters, 4(2), pp.583-590.

nanoGe is a prestigious brand of successful science conferences that are developed along the year in different areas of the world since 2009. Our worldwide conferences cover cutting-edge materials topics like perovskite solar cells, photovoltaics, optoelectronics, solar fuel conversion, surface science, catalysis and two-dimensional materials, among many others.

MATSUS

Previously nanoGe Spring Meeting (NSM) and nanoGe Fall Meeting (NFM), MATSUS is a multiple symposia conference focused on a broad set of topics of advanced materials preparation, their fundamental properties, and their applications, in fields such as renewable energy, photovoltaics, lighting, semiconductor quantum dots, 2-D materials synthesis, charge carriers dynamics, microscopy and spectroscopy semiconductors fundamentals, etc.

International Conference on Hybrid and Organic Photovoltaics

International Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.

Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics

The main topics of the Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP) are discussed every year in Asia-Pacific for gathering the recent advances in the fields of material preparation, modeling and fabrication of perovskite and hybrid and organic materials. Photovoltaic devices are analyzed from fundamental physics and materials properties to a broad set of applications. The conference also covers the developments of perovskite optoelectronics, including light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.

International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics

The International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics (NIPHO) is the best place to hear the latest developments in perovskite solar cells as well as on recent advances in the fields of perovskite light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.