Nitride-Based Interfacial Layers for Monolithic Tandem Integration of New Solar Energy Materials on Si: The Case of CZTS
Filipe Martinho, Alireza Hajijafarassar, Simón Lopez-Marino, Moises Espíndola-Rodríguez, Sara Engberg, Mungunshagai Gansukh, Fredrik Stulen, Sigbjørn Grini, Stela Canulescu, Eugen Stamate, Andrea Crovetto, Lasse Vines, Jørgen Schou, Ole Hansen
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 Cu 2 ZnSnS 4 (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 ( V oc ) 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.