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Page 2 of 16 Dong et al. Energy Mater. 2026, 6, 600026

Technology, Yangzhou University, Yangzhou 225127, Jiangsu, China; Wang Zheng School of Microelectronics, Changzhou University,
Changzhou 213164, Jiangsu, China. E-mail: guohuafei@cczu.edu.cn; Dr. Jianning Ding, Institute of Technology for Carbon Neutralization,
School of Physical Science and Technology, Yangzhou University, Yangzhou 225127, Jiangsu, China. E-mail: dingjn@yzu.edu.cn

Density functional theory calculations further corroborate the role of Nd in lowering defect formation energies and
modulating the electronic structure. Moreover, Nd incorporation optimizes conduction band alignment, suppresses
Shockley-Read-Hall recombination, and improves carrier extraction. As a result, the champion device achieves a
power conversion efficiency of 9.17%, with a fill factor (FF) of 64.58%, an open-circuit voltage (V OC ) of 0.46 V, and a
short-circuit current density (J SC ) of 30.54 mA/cm . This work provides fundamental insights into doping in Q1D
2
semiconductors and offers a practical route toward high-efficiency Sb 2 Se 3 photovoltaics.

INTRODUCTION
Antimony Selenide (Sb Se ) is considered a competitive absorber material for photovoltaic applications due
3
2
to its non-toxic and abundant elemental composition, robust chemical stability, optimal bandgap, strong
light-harvesting capability, efficient charge transport, and extended carrier lifetime . Continuous progress
[1-4]
in deposition techniques and interface engineering has steadily improved the power conversion efficiency
(PCE) of Sb Se thin-film solar cells, with a record PCE of 10.57% reported by Zhao et al. in 2022 .
[5]
3
2
Nevertheless, this value remains far below the theoretical efficiency limit (> 30%) and still lags behind other
high-performance thin-film photovoltaics such as perovskite and Copper Zinc Tin Sulfide (CZTS) solar
cells , indicating that the efficiency potential of Sb Se has yet to be fully unlocked.
[6,7]
3
2
The performance of Sb Se devices is mainly limited by intrinsic material challenges, including departure
3
2
from the optimal [hk1] orientation, high densities of native defects, insufficient crystallinity, and suboptimal
interfacial band alignment [8-10] . Collectively, these limitations impede carrier transport and intensify
interfacial recombination . In semiconductor thin films, elemental doping is a well-established strategy to
[11]
tune crystal-growth kinetics, electronic structure, defect formation, and interfacial energetics [12,13] , and is
therefore considered a key route to improving Sb Se film quality and device performance. However, the
2
3
quasi-one-dimensional (Sb Se ) chain/ribbon framework, stacked along the [001] direction via van der
4
6 n
Waals interactions, creates a high energetic barrier for dopant incorporation. Consequently, foreign ions
often exhibit poor lattice incorporation and instead segregate at surfaces, grain boundaries, or inter-chain
regions [14,15] . Although various dopants, including Li, Na, K, Rb, and Cs, have been explored for Sb Se thin
3
2
films, their overall doping effectiveness remains limited [16-19] . Additionally, existing approaches such as
interfacial etching and heterojunction diffusion - including our previous work - can partially improve film or
interface properties but often introduce structural perturbations or defects to the Sb Se surface or the
2
3
cadmium sulfide (CdS) buffer layer [20,21] . These adverse effects hinder further enhancement of device
performance. Thus, it is imperative to develop a more controllable and mild doping strategy that preserves
the integrity of both the Sb Se absorber and the heterojunction structure.
2
3
Against this background, lanthanide ions have been reported to improve crystal quality, reduce defect
density, and tune band structures in Sb Se films, owing to their unique 4f electronic characteristics.
3
2
However, previous studies have mainly focused on larger lanthanide ions, such as Ce , whose relatively large
3+
ionic radius often induces noticeable lattice distortion during processing, thereby limiting the achievable
material improvements . In contrast, Nd possesses a smaller ionic radius, making it theoretically more
[22]
3+
favorable for strain relief and structural optimization in Sb Se . Nevertheless, under conventional
2
3
hydrothermal conditions, Nd tends to alter the chemical environment of the precursor solution and fails to
3+
be effectively incorporated into the film, instead remaining at surfaces or grain boundaries and thereby
severely restricting its beneficial role .
[23]