Double-Mesoscopic HTM-Free Perovskite Solar Cells: Overcoming Charge Transport Limitation by Sputtered 40 nm Al2O3 Isolation Layer
Gayathri Mathiazhagan a c, Lukas Wagner a, Shankar Bogati a, Kübra Yasaroglu Ünal a d, Thomas Kroyer a, Simone Mastroianni a b, Andreas Hinsch a
a Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstraße 2, D-79110 Freiburg, Germany
b Freiburg Materials Research Center FMF, Albert-Ludwigs-University Freiburg, Stefan-Meier-Straße 25, D-79140 Freiburg, Germany
c Department of Microsystems Engineering (IMTEK), Albert-Ludwigs-University Freiburg, Georges-Köhler-Allee 103, D-79110 Freiburg im Breisgau, Germany
d IPCMS, Université de Strasbourg, CNRS UMR 7504, 23 rue du Loess, B. P. 43, 67034 Strasbourg Cedex 2, France
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP20)
Tsukuba-shi, Japan, 2020 January 20th - 22nd
Organizers: Michio Kondo and Takurou Murakami
Poster, Simone Mastroianni, 083
Publication date: 14th October 2019

The electrically insulating space layer covers a fundamental role in monolithic carbon-graphite based PSCs and it has been established to prevent the charge recombination of electrons at the mp‑TiO2/carbon-graphite (CG) interface. Thick 1 µm printed layers are commonly used for this purpose in the established triple-mesoscopic structures to avoid ohmic shunts and to achieve a high open circuit voltage [1]. In this work, we have developed a reproducible large-area procedure to replace this thick space layer with an ultra-thin dense 40 nm sputtered Al2O3 which acts as highly electrically insulating layer preventing ohmic shunts. Herewith transport limitations related so far to the hole diffusion path length inside the thick mesoporous space layer have been omitted by concept. The thickness has been finely tuned for the optimal infiltration of the perovskite solution allowing full percolation and crystallization. This will pave the way towards the development of next generation double-mesoscopic carbon‑graphite based PSCs with highest efficiencies. Table of Contents (TOC) graphic (a) shows the cross-sectional scanned electron microscope (SEM) image where the presence of Al2O3 is seen. TOC (b) shows that the photogenerated electrons cannot pass through Al2O3 thereby preventing the charge recombination at the mp-TiO2/CG interface. Photo voltage (VOC) decay, light-dependent and time-dependent photoluminescence measurements showed that the optimal 40 nm thick Al2Onot only prevents ohmic shunts but also reduces the charge recombination at the mp-TiO2/CG interface efficiently. A stable VOC of 1 V using MAPbI3 perovskite has been achieved under full sun AM 1.5 with stabilized device performance of 12.1%

This work has been partially funded by the Project PROPER financed from the German Federal Ministry of Education and Research under the funding number 01DR19007. In addition it was funded by the project UNIQUE, supported under the umbrella of SOLAR-ERA.NET_Cofund by ANR, PtJ, MIUR, MINECO-AEI, SWEA. SOLAR-ERA.NET is supported by the European Commission within the EU Framework Programme for Research and Innovation HORIZON 2020 (Cofund ERA-NET Action, N° 691664). This research has further received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 763989 APOLO. D.B. and L.W. acknowledge the scholarship support of the German Federal Environmental Foundation (DBU). G.M. acknowledges the scholarship support of State Graduate Funding Program of Baden-Würrtemberg (LGFG).

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