Fengzhen Liu

Solar Cells

University of Chinese Academy of Sciences,Yuquan Road 19(A), Beijing 100049

Email: liufz@ucas.ac.cn

Biography

Abstract for Presentation

Crystalline Silicon/Compound Heterojunction Solar Cells with Dopant-free Carrier Selective Transport Layers

Different from the traditional silicon heterojunction (SHJ) solar cells relying on doped silicon layers, crystalline silicon/compound heterojunction (SCH, or dopant-free asymmetric heterocontacts DASH) solar cells use wide band-gap materials with extreme work-function values to realize the carrier selectivity.[1-3] Due to the avoidance of optoelectronic losses and technological limitations caused by doped silicon, the SCH solar cells show the potential of both high efficiency and low cost. Many different compound materials, including transition metal oxides, alkali metal fluorides, and some organic semiconductors, have been demonstrated to form efficient carrier selective contacts on c-Si and the reporting efficiency has been improved to 23.5%.[4]

In our group, materials with high work-function values, including MoOx, WOx, VOx, and PEDOT:PSS, and materials with low work-function values, including ZnOx, SnOx, TiOx, LiF, MgF2 and PCBM, are respectively used to serve as the hole and electron selective transport layers of the SCH solar cells.[5-12] Some simple fabrication techniques including solution process, thermal evaporation, electron beam evaporation, atomic layer deposition, and hot wire oxidation-sublimation deposition (HWOSD, developed in our group) are adopted to prepare these materials. The temperature during the entire fabrication process of the solar cells is below 200°C, which makes the fabrication process flexible. Based on n type and p type c-Si substrates, the SCH solar cells with various configurations including front-junction, back-junction, double-side, and interdigitated back contact have been fabricated. Efficiencies above 20% have been achieved for most of the SCH solar cells. Using ICO (indium-cerium-oxide), deposited by reactive plasma deposition technique, as front transparent conductive oxide (TCO) layer, we accomplish an implied open circuit voltage (iVOC) of 764 mV and an implied fill factor (iFF) of 82.5% on a large size SCH device (166 mm ´166 mm) with MoOx hole transport layer and intrinsic a-Si:H passivation layer. As a kind of c-Si solar cells with passivating contacts, interface passivation is critical important for the SCH solar cells. Transport mechanisms investigation shows that, with good interface passivation, a strong inversion layer is induced in the c-Si substrates of the SCH solar cells by the huge work-function difference. The potential of the SCH solar cells is prospected.

References

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[6]    M. Liu, Y. Zhou, G. Dong, W. Wang, J. Wang, C. Liu, F. Liu, D. Yu,  Solar Energy Mater. Solar Cells 200(2019) 109996.
[7]    F. Li, Z. Sun, Y. Zhou, Q. Wang, Q. Zhang, G. Dong, F. Liu, Z. Fan, Z. Liu, Z. Cai, Y. Zhou, D. Yu,  Solar Energy Mater. Solar Cells 203(2019)110196.
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[12]     R. Shen，Z. Sun，Y. Zhou，Y. Shi, J. Shang, H. Chen, Y. Zhou, F. Liu, Pro. Photovolt. Res. Appl. 30 (2022) 661.