Finding the Most Promising Route for All-Inorganic Perovskites with PL Measurements: The PCE Potential of the Most Relevant Compositions and Transport Layers

Max Grischek^a^,^b, Pietro Caprioglio^a^,^b, Hannes Hempel^c, José Antonio Márquez Prieto^c, Ivona Kafedjiska^d, Thomas Unold^c, Iver Lauermann^d, Martin Stolterfoht^b, Dieter Neher^b, Steve Albrecht^a^,^e

^aHelmholtz-Zentrum Berlin für Materialien und Energie GmbH, Young Investigator Group Perovskite Tandem Solar Cells, Berlin, Germany

^bUniversity of Potsdam, Institute of Physics and Astronomy, Karl-Liebknecht-Str 24-25, Potsdam, 14476, Germany

^cHelmholtz-Zentrum Berlin, Department Structure and Dynamics of Energy Materials, Berlin, Germany

^dHelmholtz-Zentrum Berlin, Competence Centre Photovoltaics (PVcomB), Berlin, Germany

^eTechnical University Berlin, Faculty IV – Electrical Engineering and Computer Science, 10587 Berlin, Germany.

Materials for Sustainable Development Conference (MATSUS)
Proceedings of Online nanoGe Fall Meeting 20 (OnlineNFM20)

#PerFun20. Perovskite I: Solar Cells and Related Optoelectronics

Online, Spain, 2020 October 20th - 23rd

Organizers: Mónica Lira-Cantú and Mohammad Nazeeruddin

Contributed talk, Max Grischek, presentation 175
Publication date: 4th October 2020

All-inorganic perovskite compositions are highly interesting for solar cell application due to their outstanding thermal stability and tandem-relevant band gap. Although efficiencies over 19 % have been achieved[1], all-inorganic perovskite solar cells still lag behind their organic-inorganic counterparts. These lower efficiencies are largely due to lower open-circuit voltages compared to organic-inorganic perovskites with the same band gap.

This study investigates the efficiency potential of all-inorganic perovskite layers using intensity-dependent photoluminescence (PL) measurements. This contact-less measurement of a neat absorber film or a layer stack allows for the construction of a pseudo JV curve, providing potential performance metrics such as open-circuit voltage (V_OC) and fill factor[2]. Based on realistic assumptions on photocurrent generation, an efficiency potential of the film or stack can be calculated. This is a powerful tool to compare the potential of perovskite compositions and transport layers and to identify the dominating loss mechanisms.

For this presentation, DMAI-CsPbI₃ films[1] with a band gap of 1.73 eV are fabricated and analysed. Neat films on quartz glass show a PL-derived efficiency potential of 24.2 %, a remarkable value that for the first time quantifies a potential that can be achieved with ideal transport layers. Films on top of a bilayer of compact and mesoporous TiO₂ still show an efficiency potential of 22.9 %.

In addition, CsPbI₂Br films with a band gap of 1.9 eV are fabricated and compared to CsPbI₃ films. Films on top of the self-assembled monolayer (SAM) molecule 2PACz show a very high PL quantum yield (PLQY) of above 12 %. In a previous study on organic-inorganic perovskites, only potassium-passivated triple cation perovskite films showed a higher PLQY[2]. With the measured quasi-Fermi level splitting (QFLS) of 1.54 eV, 97 % of the radiative V_OC limit was reached, which is on par with the best organic-inorganic films we measured[2]. The resulting efficiency potential of 22.8 % is surprisingly close to the efficiency potential of CsPbI₃ on TiO₂ (22.9 %), which has a much lower band gap. These findings suggest very low defect density both in the CsPbI₂Br perovskite bulk and at the interface between perovskite and contact layer.

This study shows very high efficiency potentials that can be achieved with ideal transport layers. By comparing the most relevant compositions and transport layers, this study helps to identify the most promising route for all-inorganic perovskites and the main loss-inducing interfaces.

References:

[1] Y. Wang et al., “The Role of Dimethylammonium Iodide in CsPbI3 Perovskite Fabrication: Additive or Dopant?,” Angew. Chemie Int. Ed., vol. 58, no. 46, pp. 16691–16696, Nov. 2019.

[2] M. Stolterfoht et al., “How To Quantify the Efficiency Potential of Neat Perovskite Films: Perovskite Semiconductors with an Implied Efficiency Exceeding 28%,” Adv. Mater., vol. 32, no. 17, p. 2000080, 2020.

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