Nitride-Based Interfacial Layers for Monolithic Tandem Integration of New Solar Energy Materials on Si: The Case of CZTS

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.

Interface Recombination of Cu2ZnSnS4 Solar Cells Leveraged by High Carrier Density and Interface Defects

“…[7,8] Moreover, pure-sulfide CZTS is also one of the most promising candidates as the top cell for silicon-based tandem solar cells, potentially triggering further technological evolution for largescale deployment of PV technologies. [9][10][11] Nevertheless, the current status of CZTS thin-film solar cells suffers from a much more open-circuit voltage (V OC ) loss than low-bandgap Cu 2 ZnSnS,Se 4 (CZTSSe) solar cells. [3,12,13] Besides the more severe bandgap/potential fluctuation and shorter photoluminescence (PL) decay time (related to real minority carrier lifetime), [14][15][16] the unfavorable "cliff"-like conduction band offset (CBO) at CZTS/CdS heterojunction interface is well believed to be a serious limiting factor to the V OC of CZTS solar cells.…”

Challenges for the future of tandem photovoltaics on the path to terawatt levels: a technology review

“…Therefore, a diffusion barrier is likely needed, limiting the prospects of epitaxial growth. This has been a recent topic of research [109,110].…”

Boosting the Efficiency of CZTS/Si Tandem Solar Cells Using In2O3 Layer in CZTS Top Cell

“…First, the core of the structure consists of two solar cells (CZTS solar cell and Si solar cell) with an intermediate connection. Second, the top and bottom electrodes which TCO-less tandem DSSC 7.1 [21] DSSC/CIGS 12.35 [22] DSSC/GaAs 7.63 [23] DSSC/c-Si 17.23 [24] DSSC/a-Si 18.1 [25] Perovskite/c-Si 23.6-26.4 [ 26,27] CZT/Si 16.8-34.1 [28] CZTS/Si 3.5-15 [ 5,29,30] Structures dimensions and materials properties are given in Table 2. As shown in Table 2, the studied structures are thin film solar cells.…”