Publication date: 15th December 2025
Perovskite solar cells (PSCs) can achieve high power conversion efficiency (PCE) in both standalone devices and tandem architectures. Particularly in this latter configuration, PCE values range from 23% to 35% depending on the bottom device (organic, chalcogenide, silicon). Silicon-based tandem devices offer high performance but must be produced on rigid substrates; chalcogenide- and organic-based tandem devices, on the other hand, enable implementation on flexible substrates. Indeed, chalcogenide-based bottom devices are well-suited to meet the requirements of PSCs production. Unfortunately, the most performing chalcogenides have other limitations, such as high prices and poor component repeatability (Cu(In,Ga)S2) or high toxicity (CdTe). But kesterite can offer a way out: it is a chalcogenide composed of earth-abundant, non-toxic elements, exhibits high stability, and has a tunable bandgap. Among them, Cu2ZnSn(S,Se)4 (CZTSSe), with a band gap of about 1.1 eV, is an ideal bottom-cell candidate for tandem devices with perovskites. However, if kesterite can offer low cost and high component availability, the non-outstanding stand-alone device performance (below 16%) still limits advancement in CZTSSe/perovskite tandem.
This study introduces an efficient solution-processed route for fabricating CZTSSe bottom cells on both rigid soda-lime glass (SLG) and flexible molybdenum foil substrates. Incorporating sodium and partially substituting copper with silver enhanced the absorber’s morphology and grain growth, resulting in high-quality thin films. The architecture of the 4-terminal (4T) tandem devices was refined by pairing these optimized kesterite bottom cells with semi-transparent perovskite top cells. Perovskites with various band gaps and compositions were also explored to achieve optimal bandgap alignment between the two subcells and broaden the usable spectral range. Efficiencies above 20% were obtained for both rigid and flexible 4T tandems, highlighting the strong compatibility of these two thin-film photovoltaic materials. Therefore, fabrication of 2-terminal tandem devices has begun, with a focus on optimizing those produced on flexible substrates. The results are encouraging and should spur the search for low-cost and easily produced materials for tandem applications in integrated photovoltaics.
The authors thank Eni S.p.A. for funding C.G.’s PhD scholarship. The article is based on work from COST Action Research and International Networking project "Emerging Inorganic Chalcogenides for PVs (RENEW-PV)," CA21148, supported by COST (European Cooperation in Science and Technology).The research projects “nuovi Concetti, mAteriali e tecnologie per l’iNtegrazione del fotoVoltAico negli edifici in uno scenario di generazione diffuSa” [CANVAS], funded by the Italian Ministry of the Environment and the Energy Security, through the Research Fund for the Italian Electrical System (type-A call, published on G.U.R.I. n. 192 on 18-08- 2022), and the “MUSA—Multilayered Urban Sustainability Action” project, funded by the European Union, via NextGenerationEU, under the National Recovery and Resilience Plan (NRRP) Mission 4 Component 2 Investment Line 1.5: Strengthening of research structures and creation of R&D “innovation ecosystems”, set up of “territorial leaders in R&D” supported the work.
nanoGe is a prestigious brand of successful science conferences that are developed along the year in different areas of the world since 2009. Our worldwide conferences cover cutting-edge materials topics like perovskite solar cells, photovoltaics, optoelectronics, solar fuel conversion, surface science, catalysis and two-dimensional materials, among many others.
Previously nanoGe Spring Meeting (NSM) and nanoGe Fall Meeting (NFM), MATSUS is a multiple symposia conference focused on a broad set of topics of advanced materials preparation, their fundamental properties, and their applications, in fields such as renewable energy, photovoltaics, lighting, semiconductor quantum dots, 2-D materials synthesis, charge carriers dynamics, microscopy and spectroscopy semiconductors fundamentals, etc.
International Conference on Hybrid and Organic Photovoltaics
International Conference on Hybrid and Organic Photovoltaics (HOPV) is celebrated yearly in May. The main topics are the development, function and modeling of materials and devices for hybrid and organic solar cells. The field is now dominated by perovskite solar cells but also other hybrid technologies, as organic solar cells, quantum dot solar cells, and dye-sensitized solar cells and their integration into devices for photoelectrochemical solar fuel production.
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
The main topics of the Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP) are discussed every year in Asia-Pacific for gathering the recent advances in the fields of material preparation, modeling and fabrication of perovskite and hybrid and organic materials. Photovoltaic devices are analyzed from fundamental physics and materials properties to a broad set of applications. The conference also covers the developments of perovskite optoelectronics, including light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.
The International Conference on Perovskite Thin Film Photovoltaics Perovskite Photonics and Optoelectronics (NIPHO) is the best place to hear the latest developments in perovskite solar cells as well as on recent advances in the fields of perovskite light-emitting diodes, lasers, optical devices, nanophotonics, nonlinear optical properties, colloidal nanostructures, photophysics and light-matter coupling.