Emerging Customized Kesterite Technologies for Next Generation PV Integration

BIPV and PIPV are identified as key enabling technologies to make “near Zero Energy Buildings” and “net Zero Energy Districts” more realistic, through the integration of a new generation of photovoltaic modules capable of entirely replacing architectural/mobility/urban-furniture passive elements. This promising scenario of mass realization of BIPV and PIPV solutions can only be achieved by developing cost-efficient and sustainable thin film technologies with unbeatable aesthetic functionalities, including mechanical flexibility and optical tuneability.<br/><br/>In this work, the main results achieved in the Custom-Art (www.custom-art-h2020.eu ) European project will be reviewed. The project has involved an intense activity on the development of advanced BIPV and PIPV modules based on earth abundant kesterite materials which are at the forefront of emerging inorganic thin film technologies. By combining advanced strategies for materials properties management with customized modules design in a circular economy approach, two types of products have been developed including flexible PV modules on polymer and steel-based substrates with different device architectures corresponding to monograin (MGL) and thin film microcrystalline solar cells. This has involved a relevant activity in the development and optimization of highly innovative cost-efficient processes for the improvement of device efficiency, stability and scalability.<br/><br/>Main results achieved in the project have included the include the optimization of the processes for highly efficient kesterite solar cells, with the demonstration at cell level of a record device efficiency of 12.06% (active area) of MGL Cu₂ZnSnS₄ solar cells that has been achieved with the modification of the absorber/buffer interface by using two-step heterojunction formation process. For the thin film microcrystalline solar cell configurations, new solution based processes have been developed leading to a record 14.1% Cu₂ZnSn(S,Se)₄ device efficiency (active area, w/o antireflective coatings). These are based on the implementation of innovative Li and Ag co-doping processes allowing for materials and device optimization. Solution and PVD highly resilient process strategies have also been demonstrated leading to device efficiencies &gt; 11%, and a strong effort has been devoted to the up-scaling of the processes up to 10x10 cm², achieving very good uniformity results that allow the transfer of these processes for the development of medium size customized modules with targeted efficiencies &gt; 10%. Transferability of the processes to flexible substrates has also been demonstrated, with efficiency results similar to those achieved on glass substrates, demonstrating monolithically interconnected flexible modules with relative efficiency loss ≤ 20% versus cell efficiency. This has allowed the design and implementation of medium size customized modules integrating novel flexible cost efficient integrating novel flexible cost efficient encapsulants based on the implementation of organic multinanolayer stacks and compatible with efficient recycling processes. Application of these processes for the development of customized modules integrated in different kinds of advanced BIPV and PIPV product demonstrators will be reviewed, and results on the assessment of the device demonstrators at real world operative conditions will be presented.