2D/3D Hybrid Cs2AgBiBr6 Double Perovskite Solar Cells: Improved Energy Level Alignment for Higher Contact-Selectivity and Large Open Circuit Voltage

Maximilian T. Sirtl (Corresponding author), Rik Hooijer, Melina Armer, Firouzeh G. Ebadi, Mahdi Mohammadi, Clément Maheu, Andreas Weis, Bas T. van Gorkom, Sebastian Häringer, René A.J. Janssen, Thomas Mayer, Vladimir Dyakonov, Wolfgang Tress, Thomas Bein (Corresponding author)

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

Since their introduction in 2017, the efficiency of lead-free halide perovskite solar cells based on Cs2AgBiBr6 has not exceeded 3%. The limiting bottlenecks are attributed to a low electron diffusion length, self-trapping events and poor selectivity of the contacts, leading to large non-radiative VOC losses. Here, 2D/3D hybrid double perovskites are introduced for the first time, using phenethyl ammonium as the constituting cation. The resulting solar cells show an increased efficiency of up to 2.5% for the champion cells and 2.03% on average, marking an improvement by 10% compared to the 3D reference on mesoporous TiO2. The effect is mainly due to a VOC improvement by up to 70 mV on average, yielding a maximum VOC of 1.18 V using different concentrations of phenethylammonium bromide. While these are among the highest reported VOC values for Cs2AgBiBr6 solar cells, the effect is attributed to a change in recombination behavior within the full device and a better selectivity at the interface toward the hole transporting material (HTM). This explanation is supported by voltage-dependent external quantum efficiency, as well as photoelectron spectroscopy, revealing a better energy level alignment and thus a better hole-extraction and improved electron blocking at the HTM interface.

Original languageEnglish
Article number2103215
Number of pages12
JournalAdvanced Energy Materials
Volume12
Issue number7
Early online date9 Jan 2022
DOIs
Publication statusPublished - 17 Feb 2022

Bibliographical note

Funding Information:
The authors acknowledge funding from the German Federal Ministry of Education and Research (BMBF) under the agreement number 03SF0516B, the Bavarian Ministry of the Environment and Consumer Protection, the Bavarian Network “Solar Technologies Go Hybrid”, the German Science Foundation (DFG) focus program SPP 2196 and the DFG Excellence Cluster e‐conversion (EXC 2089/1‐390776260). The authors thank Dr. Steffen Schmidt for performing the SEM measurements.

Keywords

  • 2D perovskites
  • 2D/3D hybrid perovskites
  • Cs2AgBiBr6, double perovskites
  • solar cells
  • Cs AgBiBr
  • double perovskites

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