MRS Meetings and Events


EN05.10.32 2023 MRS Fall Meeting

Bandgap Optimization by Cu Doping of Ag-In Halide Double Perovskites for Photovoltaic Applications

When and Where

Nov 29, 2023
8:00pm - 10:00pm

Hynes, Level 1, Hall A



Shunnosuke Ikegaya1,Koji Yokoyama1,Shun Yokoyama1,Hideyuki Takahashi1

Tohoku University1


Shunnosuke Ikegaya1,Koji Yokoyama1,Shun Yokoyama1,Hideyuki Takahashi1

Tohoku University1
Lead iodide perovskites (APbI<sub>3</sub>, where A represents organic cations) have been used as photoactive layers in perovskite photovoltaics due to their excellent optical and electronic properties. However, the toxicity of Pb and the ambient instability caused by the degradation of organic cations and iodide anions have hindered their widespread use. Metal halide double perovskites (A<sub>2</sub>B<sup>I</sup>B<sup>III</sup>X<sub>6</sub>, where B<sup>I</sup>, B<sup>III</sup>, and X represent monovalent and trivalent metal cations, and halide anions, respectively) have been theoretically proposed as Pb-free halide perovskites. Theoretical calculations predict that Rb<sub>2</sub>CuInCl<sub>6</sub> double perovskites have a direct and optimal bandgap of 1.36 eV, whereas they cannot be synthesized directly due to their low thermodynamic stability. Instead, we focused on Cs<sub>2</sub>AgInCl<sub>6</sub> double perovskites, which can be synthesized directly and exhibit superior ambient stability; however, they have a large bandgap (&gt;3.0 eV), making them unsuitable for photoactive layers. Recent studies have reported that Cu<sup>2+</sup> doping reduces the bandgap of Cs<sub>2</sub>AgInCl<sub>6</sub> from 3.0 to 2.2 eV. Furthermore, it was demonstrated that Cu<sup>+</sup>-Cu<sup>2+</sup>-In<sup>3+</sup>-based layered perovskites exhibited better optical properties than perovskites composed of Cu<sup>+</sup> or Cu<sup>2+</sup> alone. In this study, we present the synthesis of Ag-In double perovskites with an optimal bandgap as photoactive layers through Cu<sup>+/2+</sup> doping.<br/>All of the following processes were performed at 75°C in ambient air. Ag-In precursor aqueous solutions (denoted as S1) were prepared by dissolving AgCl and InCl<sub>3</sub>・4H<sub>2</sub>O in concentrated HCl. Precursor aqueous solutions containing only Cu<sup>2+</sup> (denoted as S2) were prepared by dissolving CuCl<sub>2</sub>・2H<sub>2</sub>O in concentrated HCl. Precursor aqueous solutions containing only Cu<sup>+</sup> (denoted as S3) were prepared by dissolving CuCl with reductants in concentrated HCl. Precursor aqueous solutions containing Cu<sup>+</sup> and Cu<sup>2+</sup> simultaneously (denoted as S4) were prepared by dissolving CuCl and/or CuCl<sub>2</sub>・2H<sub>2</sub>O with reductants in concentrated HCl. Ultraviolet-visible (UV-Vis) absorption spectra of the S2-S4 solutions were measured to evaluate the valence states and complex structures of Cu species in these solutions. The solid samples precipitated by adding CsCl into the S1 solutions, the S1/S2 mixtures, the S1/S3 mixtures, or the S1/S4 mixtures were collected and washed. The composition, structure, and bandgap of the resulting samples were evaluated by inductively coupled plasma-mass spectrometry (ICP-MS), X-ray diffraction (XRD), and optical absorption measurements.<br/>The S2, S3, and S4 solutions turned yellow, colorless, and dark, respectively. The UV-Vis spectra of these solutions indicated that the S2 and S3 contained only [Cu<sup>II</sup>Cl<sub>4</sub>]<sup>2-</sup> and [Cu<sup>I</sup>Cl<sub>4</sub>]<sup>3- </sup>complexes, respectively, whereas the S4 contained mixed-valence Cu<sup>+/2+</sup> species. The resulting samples from the S1 solutions were completely white in color. XRD analysis confirmed the presence of the Cs<sub>2</sub>AgInCl<sub>6</sub> phase in these samples. In contrast, the resulting samples from the S1/S2 and the S1/S3 mixtures were yellow and pale yellow, respectively. These samples had a smaller bandgap compared to Cs<sub>2</sub>AgInCl<sub>6</sub>. Trace amounts of Cu were detected via ICP-MS, indicating that Cu doping of the Cs<sub>2</sub>AgInCl<sub>6 </sub>can reduce the bandgap. Interestingly, the resulting samples from the S1/S4 mixtures exhibited darker colors than the samples doped with Cu<sup>+</sup> or Cu<sup>2+</sup> alone, suggesting that simultaneous Cu<sup>+/2+</sup> co-doping leads to emergent optical properties in these samples.



Symposium Organizers

Marina Leite, University of California, Davis
Lina Quan, Virginia Institute of Technology
Samuel Stranks, University of Cambridge
Ni Zhao, Chinese University of Hong Kong

Symposium Support

Enli Technology Co., LTD

APL Energy | AIP Publishing

Session Chairs

So Min Park
Lina Quan

In this Session

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Water-Assisted Morphology and Crystal Engineering of Hybrid Organic-Inorganic Halide Perovskite: Implications for Optoelectronic Properties

Self-Leveling Inks for Engineering Large Area Uniformity in High-Performance Flexography-Printed Perovskite Solar Cells

Towards Highly Efficient Fully Evaporated Perovskite/Si Tandem Solar Cells

The Outstanding Role of Dielectricity in Hybrid Solar Cell Absorbers

Controlling The Crystallization of Pure Bromide Quasi-2-Dimensional Perovskite Crystals for High Efficiency Pure-Blue Light-Emitting Diodes

Compositional Engineering of Single-Crystal Perovskite for Highly Efficient Photovoltaics

Atomistic Origin of Transparent Absorption Spectra of Halide Perovskites

Exploring a Novel Family of Conjugated Polymers for High Efficiency and Thermally Stable Perovskite Solar Cells

Charge Transfer Doping of Ruddlesden–Popper Metal–Halide Perovskites via Bulk Incorporation of Organic Molecular Dopants

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Publishing Alliance

MRS publishes with Springer Nature