Interface Passivation Schemes for Highly Efficient Inverted Perovskite Solar Cells and Two-Terminal perovskite/c-Si and perovskite/CI(G)S tandem solar cells
Paul Fassl a b, Saba Gharibzadeh a b, Marco A. Ruiz-Preciado a b, Motiur Rahman Khan a, Ahmed Farag a b, Somayeh Moghadamzadeh a b, Christoph Klein a, Ihteaz M. Hossain a b, Roja Singh a b, Ulrich W. Paetzold a b
a Light Technology Institute, Karlsruhe Institute of Technology, Engesserstrasse 13, 76131 Karlsruhe, Germany
b Institute of Microstructure Technology, Karlsruhe Institute of Technology, 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 (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Oral, Paul Fassl, presentation 140
Publication date: 20th April 2022

Inverted p-i-n perovskite solar cells (PSCs) are critical for fabricating perovskite-based tandem photovoltaics with the highest performance. However, severe non-radiative recombination at the perovskite/electron transport layer and at the grain boundaries (GBs) still limits their open-circuit voltage (VOC) and fill factor (FF) as compared to their n-i-p counterparts. Here, we present our recent progress on developing advanced passivation schemes to manage the detrimental defects both in the GBs and the surface of the perovskite layer and discuss their application in single-junction PSCs as well as two-terminal (2T) perovskite/c-Si and perovskite/CI(G)S tandem solar cells.

First, we present our recently developed dual passivation approach using phenethylammonium chloride (PEACl) to simultaneuosly passivate the GBs and the perovskite/C60 interface by using PEACl:PbCl2 as the additive and PEACl for surface treatment, respectively. [1] Employing the self-assembled monolayer [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) as hole-transporting layer and a methylammonium-free Cs0.18FA0.82PbI3 perovskite absorber (bandgap ~1.57 eV), we achieve a substantially enhanced charge carrier lifetime and quasi-Fermi level splitting (~63 mV enhancement) compared to reference devices. We attribute the positive effects to the formation of a very thin heterogeneous 2D Ruddlesden Popper (PEA)2(Cs1−xFAx)n−1Pbn(I1−yCly)3n+1 phase with n~1-2 at the GBs and film surface. Our dual passivation strategy results in one of the highest reported PCEs for p-i-n PSCs of 22.7% with a remarkable VOC and FF of 1.162 V and 83.2%, respectively. [1]

Second, we will provide insights into our recent progress on developing passivation schemes for wider bandgap PSCs (bandgap ~1.68 eV) and discuss their impact on the efficiency and long-term stability of single-junsction PSC as well as 2T perovskite/c-Si and perovskite/CI(G)S tandem solar cells. We discuss the critical challenges for both tandem architectures as compared to single-junction PSCs and advance the current understanding on the interface passivation mechanisms using various characterization methods, such as photoluminescence quantum yield, transient photoluminescence, impedance spectroscopy, photo-CELIV, temperature dependent thermal admittance spectroscopy, capacitance-voltage measurements and others. Thereby, we contribute to the further development of highly efficient perovskite-based tandem photovoltaics.

We thank our project partners ISFH, TNO and ZSW for providing the Si and CI(G)S bottom solar cells employed for fabrication of 2T tandem solar cells.

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