Source Material Design for Realizing >50% Indium-Saving Transparent Electrode toward Sustainable Development of Silicon Heterojunction Solar Cells

Zhongyu Gao; Can Han; Jiejun Pan; Jiajun Shen; Zhibin Liu; Kaixuan Chen; Zhikai Yi; Yong Zhang; Zhong Yu; Xianjie Zhou; Pingqi Gao

doi:10.1021/acsami.4c15684

Source Material Design for Realizing >50% Indium-Saving Transparent Electrode toward Sustainable Development of Silicon Heterojunction Solar Cells

ACS Appl Mater Interfaces. 2025 Jan 3. doi: 10.1021/acsami.4c15684. Online ahead of print.

Authors

Zhongyu Gao^{1

2}, Can Han^{1

2}, Jiejun Pan^{1

2}, Jiajun Shen^{1

2}, Zhibin Liu^{1

2}, Kaixuan Chen^{1

2}, Zhikai Yi³, Yong Zhang³, Zhong Yu³, Xianjie Zhou⁴, Pingqi Gao^{1

2}

Affiliations

¹ School of Materials, Shenzhen Campus of Sun Yat-sen University, No. 66, Gongchang Road, Guangming District, Shenzhen, Guangdong 518107, P.R. China.
² Institute for Solar Energy Systems, Guangdong Engineering Technology Research Center for Sustainable Photovoltaic Technology and Equipment, State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Engineering Technology Research Centre for Advanced Thermal Control Material and System Integration (ATCMSI), Sun Yat-sen University, Guangzhou 510275, P.R. China.
³ Shenzhen S.C New Energy Technology Corporation, No. 62, Jinniu East Road, Shenzhen, Guangdong 518118, P.R. China.
⁴ Shenzhen APG Material Company Limited, No. 43, Matian North Road, Shenzhen, Guangdong 518106, P.R. China.

PMID: 39749871
DOI: 10.1021/acsami.4c15684

Abstract

Indium (In) reduction is a hot topic in transparent conductive oxide (TCO) research. So far, most strategies have been focused on reducing the layer thickness of In-based TCO films and exploring In-free TCOs. However, no promising industrial solution has been obtained yet. In our work, we adopt the emerging reactive plasma deposition (RPD) approach and provide our In-reduced solution by directly reducing the In content from the source material. We designed the indium zinc oxide (IZO) target with a composition of Zn₃In₂O₆ (i.e., (ZnO)₃·In₂O₃). Density functional theory (DFT) calculation shows that the introduction of a large amount of ZnO significantly perturbs the conduction band of the In₂O₃ host, resulting in a limitation of exploring high-mobility IZO films. For TCOs used in solar cell application, low resistivity with high carrier mobility is required. Via RPD process optimization, we obtained the minimal resistivity value of 6.08 × 10^-4 Ω·cm, which is comparable to our lab-standard tin-doped indium oxide (ITO) film. The corresponding electron mobility and carrier concentration are 31 cm² V^-1 s^-1 and 3.37 × 10²⁰ cm^-3, respectively. Our IZO film is in an amorphous state. The optical band gap is ∼3.6 eV. X-ray photoelectron spectroscopy (XPS) data show that the film composition is In:Zn:O = 21.60:28.75:49.65 (at. %). Damp heat tests show strong stability of our IZO film, and no aging effects have been observed. Furthermore, we demonstrated wafer-scale silicon heterojunction (SHJ) solar cells with IZO films. As compared with our reference hydrogenated cerium-doped indium oxide (ICO)-based solar cells, the IZO-based devices show even higher fill factor parameters. Our amorphous state stable In-reduced IZO film could find versatile application in the sustainable development of temperature-sensitive devices such as SHJ and perovskite/silicon tandem solar cells, as well as flexible OLEDs.

Keywords: indium zinc oxide (IZO); indium-reduced target; reactive plasma deposition (RPD); silicon heterojunction (SHJ) solar cell; transparent conductive oxide (TCO).