Upscalable All-Evaporated Perovskite Solar Cells Based on Inorganic Hole Transport Layers
Tobias Abzieher a, Jonas A. Schwenzer a, Florian Sutterlüti a, Michael Pfau a, Erwin Lotter b, Michael Hetterich a, Uli Lemmer a c, Michael Powalla a b, Ulrich W. Paetzold a c
a Karlsruhe Institute of Technology, Light Technology Institute (LTI), Engesserstrasse 13, 76131 Karlsruhe, Germany
b Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW), Stuttgart, Meitnerstraße, 1, Stuttgart, Germany
c Karlsruhe Institute of Technology, Institute of Microstructure Technology (IMT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV18)
Benidorm, Spain, 2018 May 28th - 31st
Organizers: Emilio Palomares and Rene Janssen
Oral, Tobias Abzieher, presentation 058
DOI: https://doi.org/10.29363/nanoge.hopv.2018.058
Publication date: 21st February 2018

With demonstrated power conversion efficiencies close to 23%, perovskite-based photovoltaics is already able to compete with established technologies like silicon, CdTe and CIGS. However, next to high efficiencies, the potential low-cost fabrication of devices with sufficient stability under real-world conditions is of key importance for the future economic prospects of the perovskite technology.

In this contribution, we report on a novel inexpensive architecture for efficient and highly reproducible, all-evaporated perovskite solar cells. Our evaporated CH3NH3PbI3 absorber is sandwiched in a p-i-n structure between inexpensive and highly stable nickel oxide as hole transport material and a combination of C60 and bathocuproine (BCP) as electron hole transport material. In contrast to that, most of the approaches in the community employ highly expensive hole transport materials like Spiro-MeOTAD or PTAA with prices up to 1,000,000 $/kg, which would hamper the commercialization of the technology. Most importantly, the common organic hole transport material Spiro-MeOTAD shows low stability at elevated temperatures above 60 °C, making it an unsuitable choice for applications under typical outdoor conditions. By replacing the unfavorable Spiro-MeOTAD by electron-beam deposited nickel oxide and the gold back electrode by copper, we reduce the cost of materials on the lab-scale to one third of the price of common stacks (e.g., ITO/TiO2/CH3NH3PbI3/Spiro-MeOTAD/Au). At the same time, power conversion efficiencies of the devices reach stabilized values above 14% without hysteresis. Moreover, high thermal stability of the employed transport materials is demonstrated in extremely stable devices even at 80 °C, which is a typical operating temperature for solar modules under real-world situations as well as standard test condition in established performance tests. In contrast, our reference all-solution-based devices with Spiro-MeOTAD degrade fast to about 80% of their initial values under the same conditions.

Towards an industrialization of the perovskite technology, a highly controllable deposition and an easy upscaling is needed. Our all-evaporated approach is able to meet these criteria. Even on small lab-scale areas, 30% lower cell-to-cell variations in comparison to common spin-coating approaches are achieved. In terms of upscaling, homogenous and reproducible depositions up to areas of 8x8 cm² are demonstrated and investigated by light beam induced current mapping. Finally, as an inverted architecture with the anode deposited on top of the substrate the discussed layer stack is a promising candidate for two-terminal tandem cells and modules on top of CIGS or p-type silicon.

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