MRS Meetings and Events


EN05.10.30 2023 MRS Fall Meeting

Efficient Perovskite Solar Cells with Improved Carrier Transport via Composition-Graded Titanium Oxynitride Electron Transport Layer

When and Where

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

Hynes, Level 1, Hall A



Yonghoon Jung1

Seoul National University1


Yonghoon Jung1

Seoul National University1
State-of-the-art perovskite solar cells (PSCs) have achieved power conversion efficiencies (PCEs) exceeding 25% by enhancing the charge transport layers to facilitate efficient carrier transport while minimizing non-radiative recombination. The effective transport of charge carriers through the perovskite and the charge transport layers can improve the fill factor and open-circuit voltage. An ideal electron transport layer (ETL) should possess complete and conformal coverage, as well as optimal band alignment that facilitates efficient extraction of electrons. Additionally, the minimal defect density in charge transport layers is essential to prevent detrimental interface recombination. While TiO<sub>2</sub> has been widely used as an ETL, it exhibits limitations as an ideal ETL due to an energy level mismatch and relatively poor electrical characteristics. Specifically, the conduction band minimum (CBM) of TiO<sub>2</sub> is slightly higher than that of MAPbI<sub>3</sub>, leading to a significant energy barrier for electron extraction. Additionally, the relatively low conductivity and mobility of TiO<sub>2</sub> hinder efficient charge transfer. To address the limitations of TiO<sub>2</sub>, metal doping such as Nb, Al, and Li has been employed to modify its electronic band structures and improve its electrical properties.<br/>In this study, nitrogen is incorporated into TiO<sub>2</sub> using the pulsed laser deposition (PLD) method to form titanium oxynitride (TiO<sub>x</sub>N<sub>y</sub>), resulting in enhanced electron transport characteristics including minimal defect density. Controlled substrate temperature and oxygen partial pressure during the deposition facilitated the achievement of optimal thin-film characteristics, including high transparency typical of TiO<sub>2</sub> semiconductors and high conductivity typical of nitrogen-rich TiN. Furthermore, TiO<sub>x</sub>N<sub>y</sub> thin films with graded atomic ratio nitrogen to oxygen (N/O) are achieved by sequentially changing the oxygen partial pressure during the process. The graded TiO<sub>x</sub>N<sub>y</sub> thin film exhibits characteristics that enable the achievement of superior functionality as an ETL compared to TiO<sub>x</sub>N<sub>y</sub> thin films without grading. By increasing the oxygen partial pressure during the deposition process, the CBM was raised, leading to a reduced energy offset with the mesoporous TiO<sub>x</sub> layer directly above it. Furthermore, TiO<sub>x</sub>N<sub>y</sub> fabricated in a multilayer structure can provide a continuous variation of energy levels within the ETL, optimizing the electron pathway and improving charge transport, ultimately enhancing charge extraction capabilities. This alignment facilitates the selective transfer of electrons to the respective electrodes while inhibiting hole transport. The accurate composition control of TiO<sub>x</sub>N<sub>y</sub> films is characterized using such as atomic force microscopy, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and Hall measurement to uncover the mechanism behind the enhanced properties. The conformally deposited films with high crystallinity and tailored optoelectrical properties exhibit effective suppression of interfacial recombination as an ETL, resulting in solar cell devices and resulting in high PCEs.


chemical composition | plasma deposition

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

Interstitial Defect Relaxation DFT Study of Lead Halide Perovskites

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

View More »

Publishing Alliance

MRS publishes with Springer Nature