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Metal Chalcogenides (PP2.4)

PP2.4 Metal Chalcogenides

 

Aims and objectives

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This work package will build on ACAP’s existing world-leading position in metal chalcogenide solar cell research to advance these technologies towards record efficiency levels of >20%, sustainability (abundant and non-toxic constituents), and robustness.

 

The full potential of chalcogenide materials will be extracted for low-bandgap single-junction solar cells suitable for niche PV market and tandem cells. This works aims to demonstrate technological flexibility (structural flexibility, transparency, bifacial architectures), as well as the demonstration of their minimodules (>100 square cm). 

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Background

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From a photovoltaic perspective, metal chalcogenides are known for their high efficiency potential, excellent durability, tuneable bandgap, and great substrate versatility (in glass, steel, and silicon). These materials can be categorised across several categories: 

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Chalcogenide-1.0 is well known for two commercialised PV technologies (i.e., CdTe and CIGS); Chalcogenide-2.0, represented by kesterite (CZTS) and antimony chalcogenide, is well recognised for its cost-effectiveness and eco-friendliness by using abundant and non-toxic, materials compliant with US Restriction of Hazardous Substances code.

 

Working with already-available production-line equipment, the upscaling of the chalcogenide-2.0 PV technologies is feasible once their efficiencies reach a market-acceptable level. The need for increasing diversity of viable PV materials for greater adaptability has encouraged a continued search for next generation through metal chalcogenides (3.0), which unites the outstanding optoelectronic properties of perovskites with the durability of chalcogenides.

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Research Activities and Plans

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The key technological challenges to achieve high efficiency of metal chalcogenide solar cells vary with material types (i.e. chalcogenide #1-3) and maturity of their development. ACAP will focus its research activities across key current research gaps.

 

PP2.4.1 Metal Chalcogenide 1.0 and 2.0

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  1. Overcoming key challenges towards >20% efficiency of chalcogenides-1.0 and -2.0 through: (1) controlling 1D-3D bulk defects and in heterointerface architecture for reduced bulk and interface recombination: (2) developing 2D device simulation model to understand the grain boundary and interface recombination: (3) integrating the 2D simulation model and advanced characterisations to understand the dominant performance-loss mechanism and develop strategies for further optimisation.

  2. Integrating high bandgap top cells, low bandgap chalcogenide bottom cells, as well as transparent electrode and intermediate layer technology, >27% efficiency flexible tandem cells are expected.

  3. Developing cost-effective and robust Cd-free buffer options with suitable band alignment for green high bandgap and low bandgap chalcogenide-1.0&2.0, respectively. Cd-free buffer options by various methods (CBD, sputtering and ALD) will be evaluated in terms of efficiency, cost, and stability.

  4. Evaluating the alkaline-induced LID issue where sodium is a must-have for high efficiency metal chalcogenides. This typical LID issue will be tackled by understanding the roles and mobility of alkaline ions under different stress (illumination, heat) by advanced nanoscale characterisation, as well as our patented strategies of modulating alkaline amounts of bulk chalcogenides. Both cell and module level LID will be evaluated.

  5. Bifacial architectures will be explored for chalcogenides. TCOs combined with barrier layer and associated back contact interface design, minimising the elemental interdiffusion while enhancing carrier collection, will be the key focus when translated to bifacial cells.            

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PP 2.4.2 Metal Chalcogenide 3.0

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This activity will include research for:

  1. Fully extracting the potential of this group of green materials by obtaining high-quality materials and evaluating key electrical and optical properties and designing device architecture accordingly based on our established device design database.

  2. By exploring additives for lower thermal budget manufacturing, we will demonstrate and evaluate devices based on the monograin membrane approach at lab scale.

  3. Extending this monograin membrane sequence to other new high bandgap and low bandgap PV materials (PP1.1), we will collaborate with CSIRO for the development of large-scale printing (PP3.4).

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PP 2.4.3 Demonstration and Evaluation of (Flexible) Minimodules

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  1. Minimodule of metal chalcogenide 1.0&2.0 (>=10x10cm) will be demonstrated by developing key technologies of monolithic interconnection, large-area uniform absorber and Cd-free buffer deposition. Alternative high throughput and low-cost screening printing of metal contact will also be evaluated for further cost-reduction. For conductive steel based flexible minimodules, alternative wafer-like interconnection will be developed.

  2. Long-term stability, life-cycle performance of minimodules will be evaluated. Commercialisation pathways towards single junction and tandem cell applications respectively will be developed.

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Investigators: Xiaojing Hao (UNSW), Martin Green (UNSW), Bram Hoax (UNSW), Ned (UNSW), Ziv Hameiri (UNSW), Anthony Chesman (CSIRO), Jacek Jasieniak (Monash), Daniel MacDonald (ANU), Mei Gao (CSIRO).

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