Publication date: 5th November 2025
Perovskite solar cells (PSCs) have rapidly advanced as a leading photovoltaic technology due to their high-power conversion efficiency and low fabrication costs. As this photovoltaic technology is now approaching deployment [1], the use of materials and processes based on abundant and locally available precursors becomes even more important, to ensure competitiveness and strategic leadership in this technological field. In Brazil, the discovery of natural reserves of columbite and tantalite minerals in recent decades has sparked interest on the development of extraction and processing routes to explore these ores [2], and on adding value to elements extracted from them, such as niobium and tantalum. Nb and Ta have similar physical and chemical properties, thus these elements tend to be found together in nature, being both of them present in columbite and tantalite ores. In this context, we explored the use of niobium and tantalum mixed oxides processed from the natural tantalite ore, and their application as a potential selective contact (ETL) for PSCs, aiming to combine functional performance with material abundance and scalability. The ETL must offer high transparency, suitable energy level alignment, and adequate electronic properties. Usually, in PSCs with the n-i-p structure, the ETL is based on SnO2 or TiO2 layers [3], but Nb2O5 has also been successfully applied in that layer [4]. Herein, we present the purification process employed to extract the Nb/Ta oxides from tantalite ore collected in natural deposits in Parelhas, RN (Brazil), and a full investigation of their structural, morphological, and electronic properties. Based on the characterizations of the obtained niobium/tantalum oxides, as well as heat treatments performed at different temperatures, we obtained a powder material that was further processed tom form inks, which were then used to prepare the ETL layer in n-i-p PSCs, achieving a PCE of 16.71%. To our knowledge, this is the first demonstration of the use of mixed niobium/tantalum oxide in PSCs.
FINEP (0139/21), CNPq (409215/2023-6), FAPESP (2017/11986-5) and Shell Brasil.
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