Esma Ugur

King Abdullah University of Science and Technology

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Stefaan De Wolf

King Abdullah University of Science and Technology

Erkan Aydın

King Abdullah University of Science and Technology

Michele De Bastiani

King Abdullah University of Science and Technology

Frédéric Laquai

King Abdullah University of Science and Technology

Thomas G. Allen

King Abdullah University of Science and Technology

Maxime Babics

King Abdullah University of Science and Technology

Jiang Liu

King Abdullah University of Science and Technology

Anand S. Subbiah

King Abdullah University of Science and Technology

Randi Azmi

King Abdullah University of Science and Technology

Furkan H. Isikgor

King Abdullah University of Science and Technology

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King Abdullah University of Science and Technology

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University of Toronto

Kootenay Association for Science & Technology

Chinese Academy of Sciences

Physical Sciences (United States)

Czech Academy of Sciences, Institute of Physics

Technical University of Munich

Lawrence Berkeley National Laboratory

Northwestern University

École Polytechnique Fédérale de Lausanne

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A Practical Efficiency Target for Perovskite/Silicon Tandem Solar Cells

ACS Energy Letters (2024)

Thomas Allen Esma Ugur Erkan Aydın Anand S. Subbiah Stefaan De Wolf

Monolithic two-terminal (2T) perovskite/silicon tandem solar cells are rapidly progressing toward higher power conversion efficiencies (PCEs), which has led to a prominent role for this technology within the photovoltaics (PV) research community and, increasingly, in industrial PV R&D. Here, we define a practical PCE target of 37.8% for 2T perovskite/silicon tandems based on metrics derived from state-of-the-art silicon and perovskite solar cells and discuss possible pathways toward that goal. It is hoped that this PCE target will serve to guide future research directions, most notably into continued improvements in the radiative efficiency of the mixed-halide perovskite top cell via bulk and surface passivation strategies.

Tandem

10.1021/acsenergylett.4c02152

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Linked Nickel Oxide/Perovskite Interface Passivation for High‐Performance Textured Monolithic Tandem Solar Cells (Adv. Energy Mater. 40/2021)

Advanced Energy Materials (2021)

Shynggys Zhumagali Furkan H. Isikgor Partha Maity Jun Yin Esma Ugur

Interface Passivation In article number 2101662, Furkan H. Isikgor, Stefaan De Wolf and co-authors develop a NiOx/perovskite interface passivation strategy using an organometallic dye (N719) molecule. It concurrently passivates both NiOx and perovskite traps and facilitates charge transport across the interface. The self-assembling nature of N719 allows conformally covering complex surfaces and fabrication of highly efficient textured perovskite/silicon tandem solar cells.

Passivation

Tandem

Nickel oxide

Interface (matter)

10.1002/aenm.202170160

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Linked Nickel Oxide/Perovskite Interface Passivation for High‐Performance Textured Monolithic Tandem Solar Cells

Advanced Energy Materials (2021)

Shynggys Zhumagali Furkan H. Isikgor Partha Maity Jun Yin Esma Ugur

Abstract Sputtered nickel oxide (NiO x ) is an attractive hole‐transport layer for efficient, stable, and large‐area p‐i‐n metal‐halide perovskite solar cells (PSCs). However, surface traps and undesirable chemical reactions at the NiO x /perovskite interface are limiting the performance of NiO x ‐based PSCs. To address these issues simultaneously, an efficient NiO x /perovskite interface passivation strategy by using an organometallic dye molecule (N719) is reported. This molecule concurrently passivates NiO x and perovskite surface traps, and facilitates charge transport. Consequently, the power conversion efficiency (PCE) of single‐junction p‐i‐n PSCs increases from 17.3% to 20.4% (the highest reported value for sputtered‐NiO x based PSCs). Notably, the N719 molecule self‐anchors and conformally covers NiO x films deposited on complex surfaces. This enables highly efficient textured monolithic p‐i‐n perovskite/silicon tandem solar cells, reaching PCEs up to 26.2% (23.5% without dye passivation) with a high processing yield. The N719 layer also forms a barrier that prevents undesirable chemical reactions at the NiO x /perovskite interface, significantly improving device stability. These findings provide critical insights for improved passivation of the NiO x /perovskite interface, and the fabrication of highly efficient, robust, and large‐area perovskite‐based optoelectronic devices.

Non-blocking I/O

Passivation

Nickel oxide

Tandem

10.1002/aenm.202101662

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Efficient blade-coated perovskite/silicon tandems via interface engineering

Joule (2024)

Anand S. Subbiah Subhashri Mannar Vladyslav Hnapovskyi Anil Reddy Pininti Badri Vishal

Interface (matter)

10.1016/j.joule.2024.09.014

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Life on the Urbach Edge

The Journal of Physical Chemistry Letters (2022)

Esma Ugur Martin Ledinský Thomas G. Allen Jakub Holovský Aleš Vlk

The Urbach energy is an expression of the static and dynamic disorder in a semiconductor and is directly accessible via optical characterization techniques. The strength of this metric is that it elegantly captures the optoelectronic performance potential of a semiconductor in a single number. For solar cells, the Urbach energy is found to be predictive of a material's minimal open-circuit-voltage deficit. Performance calculations considering the Urbach energy give more realistic power conversion efficiency limits than from classical Shockley-Queisser considerations. The Urbach energy is often also found to correlate well with the Stokes shift and (inversely) with the carrier mobility of a semiconductor. Here, we discuss key features, underlying physics, measurement techniques, and implications for device fabrication, underlining the utility of this metric.

10.1021/acs.jpclett.2c01812

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In situ electrochemical deposition of compact metal-organic framework thin films for high-resolution X-ray imaging

Matter (2024)

Jianxin Wang Tengjiao He Osama Shekhah Luis Gutiérrez‐Arzaluz Esma Ugur

Deposition

10.1016/j.matt.2024.11.030

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Charge Carrier Recombination at Perovskite/Hole Transport Layer Interfaces Monitored by Time-Resolved Spectroscopy

ACS Energy Letters (2021)

Jafar I. Khan Furkan H. Isikgor Esma Ugur Waseem Raja George T. Harrison

Carrier recombination at the interface between charge extraction layers and the perovskite photoactive layer in solar cells reduces the quasi-Fermi level splitting (QFLS) and hence the device's open-circuit voltage (VOC). Distinguishing between interfacial carrier recombination and charge extraction requires selective probing of carrier dynamics with transient optical spectroscopy techniques. However, bulk recombination, interfacial recombination, and charge extraction all contribute to the transient response, making a precise determination of individual rates challenging. Here, we compare two commonly used hole transport layers (HTLs), namely, PTAA and NiOx, adjacent to prototypical MAPI3 perovskite photoactive layers and wide-bandgap perovskites. We demonstrate that combining time-resolved photoluminescence (TR-PL) and transient absorption (TA) spectroscopy measurements can reveal recombination losses associated with the perovskite/NiOx interface, as confirmed by drift-diffusion simulations. The best performing MAPI3/PTAA-based device exhibits less nonradiative recombination and more efficient charge extraction, facilitated by favorable energy level alignment.

Charge carrier

Photoactive layer

Carrier lifetime

10.1021/acsenergylett.1c01931

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Author Correction: Sublimed C60 for efficient and repeatable perovskite-based solar cells

Nature Communications (2025)

Ahmed Ali Said Erkan Aydın Esma Ugur Zhaojian Xu Caner Değer

10.1038/s41467-025-55988-7

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