Nitride-based interfacial layers for monolithic tandem integration of new solar energy materials on Si: The case of CZTS

TL;DR

This paper demonstrates that TiN-based diffusion barriers enable the monolithic integration of CZTS solar cells on silicon, achieving competitive efficiencies and voltages while protecting the silicon bottom cell during high-temperature processing.

Contribution

The study introduces TiN-based diffusion barriers as an effective method for monolithic CZTS/Si tandem solar cells, offering a new approach to interface engineering in high-temperature processes.

Findings

Achieved open-circuit voltages up to 1.06 V.

Realized efficiencies up to 3.9%.

Demonstrated protection of silicon bottom cell during high-temperature sulfurization.

Abstract

The monolithic tandem integration of third-generation solar energy materials on silicon holds great promise for photoelectrochemistry and photovoltaics. However, this can be challenging when it involves high-temperature reactive processes, which would risk damaging the Si bottom cell. One such case is the high-temperature sulfurization/selenization in thin film chalcogenide solar cells, of which the kesterite Cu2ZnSnS4 (CZTS) is an example. Here, by using very thin (<10 nm) TiN-based diffusion barriers at the interface, with different composition and properties, we demonstrate on a device level that the protection of the Si bottom cell is largely dependent on the barrier layer engineering. Several monolithic CZTS/Si tandem solar cells with open-circuit voltages (Voc) up to 1.06 V and efficiencies up to 3.9% are achieved, indicating a performance comparable to conventional interfacial layers based on transparent conductive oxides, and pointing to a promising alternative design in solar energy conversion devices.