Breakthrough in Lead-Free BaZrS₃ Solar Cells Achieves Over 28% Efficiency with Inorganic Delafossite HTLs, Challenging Organic Alternatives
Key Insights
New research demonstrates lead-free BaZrS₃ solar cells can achieve over 28% power conversion efficiency, addressing toxicity and stability concerns of lead-halide perovskites.
Inorganic delafossite hole transport layers like CuFeO₂, CuGaO₂, and CuAlO₂ proved superior or comparable to traditional organic Spiro-OMeTAD.
SCAPS-1D simulations optimized device parameters, revealing CuFeO₂-integrated cells reached a peak efficiency of 28.35%.
This development offers a sustainable, scalable path for next-generation photovoltaics, validating delafossite HTLs for non-toxic solar absorbers.
QUERÉTARO, Mexico – Researchers at the Autonomous University of Querétaro, Mexico, have achieved a significant breakthrough in lead-free solar cell technology, demonstrating power conversion efficiencies (PCEs) exceeding 28% in BaZrS₃-based chalcogenide perovskite solar cells. This development, detailed in Inorganic Chemistry Communications on July 7, 2025, marks a crucial step towards replacing toxic lead-halide perovskites and unstable organic hole transport layers (HTLs) like Spiro-OMeTAD, addressing key challenges for the photovoltaic sector.
Lead halide perovskite solar cells have garnered attention for their rapid efficiency gains, surpassing 26% for single-junction devices. However, their commercial viability is hampered by lead toxicity and poor stability under environmental stressors such as heat, moisture, and light. The Mexican research team focused on BaZrS₃, a lead-free chalcogenide perovskite, as a promising alternative absorber material. BaZrS₃ boasts a direct bandgap of approximately 1.7 eV, strong optical absorption, exceptional structural stability, and naturally high p-type conductivity, making it a sustainable and scalable solution due to its earth-abundant elemental composition.
The study critically evaluated inorganic delafossite HTLs, specifically CuFeO₂, CuGaO₂, and CuAlO₂, as superior alternatives to conventional organic HTLs. These inorganic materials offer advantages including lower cost, enhanced thermal and chemical stability, and favorable energy band alignment with BaZrS₃. Utilizing the SCAPS-1D simulation tool, the team meticulously optimized device parameters, including absorber acceptor densities, defect concentrations, absorber thickness, and interfacial defect states at both the electron transport layer (ETL) and HTL junctions. Advanced analytical methods, such as Nyquist plots, Mott-Schottky curves, and quantum efficiency studies, provided detailed insights into charge transport dynamics and recombination behavior.
The findings indicate that careful engineering of BaZrS₃-based devices with delafossite HTLs can yield impressive PCEs. Devices integrated with CuFeO₂ achieved a remarkable PCE of 28.35%, while CuGaO₂ and CuAlO₂ configurations attained 27.83% and 25.05%, respectively. These results underscore the immense promise of inorganic delafossite HTLs, which either outperformed or matched the performance of Spiro-OMeTAD. According to Dr. Latha Marasamy, a Research Professor at the Autonomous University of Querétaro and lead researcher, this pioneering work not only validates BaZrS₃ as a high-potential, non-toxic solar absorber but also provides the first comprehensive theoretical validation of delafossite HTLs within this material system. As the renewable energy sector continues its shift away from hazardous materials, these insights are vital for developing durable, scalable, and environmentally responsible photovoltaic devices for a sustainable energy future.