New class of SrHfSe₃ chalcogenide perovskite solar cells with diverse HTMs may make more efficient solar tech

The photovoltaic industry has witnessed a remarkable breakthrough with the advent of lead halide perovskite solar cells (LHPSCs), which have achieved outstanding power conversion efficiencies (PCEs); 25% in single-junction and 29% in monolithic tandem configurations. Despite this progress, challenges such as poor long-term stability, phase degradation under light, heat, and moisture, and the toxicity of lead (Pb) remain significant obstacles to commercial scalability and environmental safety.

To overcome these limitations, my research team at the Autonomous University of Querétaro, Mexico, focused on chalcogenide perovskites, particularly SrHfSe₃, which exhibits compelling attributes for next-generation solar technology. This material offers superior chemical stability, a tunable bandgap, a high photon absorption coefficient, and enhanced p-type carrier mobility, making it an excellent candidate for photovoltaic applications.

We investigated SrHfSe₃-based chalcogenide perovskite solar cells within the device architecture FTO/BaSnO₃/SrHfSe₃/HTL/Au, initially using MoS₂, as the hole transport layer (HTL). We then systematically replaced MoS₂ with 40 different HTLs, including inorganic semiconductors, polymers, and MXenes, a novel exploration carried out for the first time by my group.

Using the SCAPS-1D simulation tool, developed by Mark Burgelman, University of Ghent, we conducted a theoretical study, simulating 1,627 device configurations. This allowed us to optimize critical parameters such as absorber acceptor density, defect density, thickness and back contact work functions, all under near-realistic conditions.

Our findings, published in Solar Energy Materials and Solar Cells, demonstrate that through meticulous device engineering, SrHfSe₃-based chalcogenide perovskites can achieve significant performance gains. The results indicate a promising path toward efficient, stable, and lead-free solar cells. Optimizations led to improved light absorption, minimized recombination losses, enhanced built-in potential, and better charge transport characteristics. Notably, enhanced band alignment and interfacial properties contributed to substantial PCE improvements.

We analyzed 41 HTLs across 1,627 solar cell configurations, categorizing them into three HTL categories. We then conducted a comparative analysis of these three types by examining the low and high-efficiency HTLs within each group using various techniques, such as capacitance-voltage (C-V), Mott-Schottky analysis, impedance spectroscopy, quantum efficiency studies, and energy band alignments.

Performance enhancements were primarily attributed to higher short-circuit current densities (J_SC), increased quasi-Fermi level splitting, improved carrier generation, stronger internal electric fields, enhanced QE, and diffusion lengths. Among the simulated configurations, the best configuration devices used SnS, CPE-K, and Ti₂CO₂ as HTMs, achieving PCEs of 27.87%, 27.39%, and 26.30%, respectively.

This research marks a promising step forward in the search for safer, high-performance alternatives to conventional perovskites. By integrating SrHfSe₃ with HTLs, the team has laid a strong foundation for developing stable, efficient, and non-toxic solar cells. As the world moves toward cleaner energy solutions, innovations like this have the potential to reshape the future of photovoltaics.

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