Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 13, Issue 41, Pages 49414-49422Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.1c11493
Keywords
CIGS; quaternary target; sputtering; back contact; thin film
Funding
- National Key R&D Program of China [2018YFBI150050302]
- Natural Science Foundation of Hebei Province [F2018201058]
- Postgraduate's Innovation Fund Project of Hebei Province [CXZZBS2019031]
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The formation of a MoSe2 intermediate layer at the Mo/Cu(In,Ga)Se-2 (CIGS) interface can effectively reduce the back-contact barrier and improve hole transport in CIGS solar cells. This study demonstrates a method of depositing a room-temperature amorphous CIGS intermediate layer on the Mo substrate, which reacts with the Mo substrate to form a thin MoSe2 layer at high temperatures. This approach enables high-efficiency CIGS solar cells without the need for a selenium atmosphere during the sputtering process.
The Schottky back-contact barrier at the Mo/Cu(In,Ga)Se-2 (CIGS) interface is one of the critical issues that restrict the photovoltaic performance of CIGS solar cells. The formation of a MoSe2 intermediate layer can effectively reduce this back-contact barrier leading to efficient hole transport. However, the selenium-free atmosphere is unfavorable for the formation of the desired MoSe2 intermediate layer if the CIGS films are prepared by the commonly used direct sputtering process. In this work, high-efficiency CIGS solar cells with a MoSe2 intermediate layer were fabricated by the direct sputtering process without a selenium atmosphere. This is enabled by an intermediate CIGS layer deposited on the Mo substrate at room temperature before being ramped to a high temperature (600 degrees C). The room-temperature-deposited amorphous CIGS intermediate layer is Se rich, which reacts with the Mo substrate and forms very thin MoSe2 at the interface during the high-temperature process. The formed MoSe2 decreased the CIGS/Mo barrier height for better hole transport. Consequently, the CIGS solar cell with an 80 nm intermediate layer achieved a power conversion efficiency of up to 15.8%, which is a benchmark efficiency for the direct sputtering process without Se supply. This work provides the industry a new approach for commercialization of directly sputtered CIGS solar cells.
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