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Cu2MnSnS4 thin films for a sustainable PV development

pubblicazioni - Presentazione

Cu2MnSnS4 thin films for a sustainable PV development

L’ottimizzazione dei parametri di crescita di film sottili di Cu2MnSnS4 (CMTS) è stata realizzata ecommentata, fino all’ottenimento di dispositivi FV funzionanti a base di questo composto. Questo calcogenuro è stato studiato in quanto possiede proprietà chimico-fisiche interessanti per lo sviluppo di celle solari fotovoltaiche fino alla scala del TW installato.

An attractive possibility for the synthesis of In- and Ga-free chalcogenides which may allow terawatt range photovoltaic (PV) applications relies on I2-II-IV-VI4 species, such as copper zinc tin sulfide, copper zinc tin selenide and their sulfur-selenium alloy. They share similar structure with the first developed chalcopyrite matrix (i.e. CuInS2): half of the In atoms is replaced with Zn and another half with Sn, resulting in the kesterite phase. A further alternative belonging to this class of materials is Cu2MnSnS4 (CMTS), which consists of abundant and non-toxic elements and shows high absorption coefficient and direct band gap suitable for PV applications.

Our works deals with CMTS thin films grown for the first time by a vacuum two-step approach: a stack of metal precursors deposited by thermal evaporation on Mo-coated soda lime glasses was annealed in sulfur vapors. The effects of the most critical growth parameters on TFs quality (homogeneity, stoichiometry and possible secondary phases) have been investigated, paying particular attention to the order of the metal precursors in the stack and to the annealing ramp.

The growth process was optimized through the study of the structural, morphological and optical properties of the grown CMTS thin films. The results of this characterization are reported and discussed. Good layer compactness, high absorption coefficient (5×104 cm-1) and direct band (1.26 eV) suitable for PV applications have been obtained.Some proof of concept PV device based on Cu-poor/Mn-rich CMTS samples was also realized and tested, confirming the potential of this emerging material as low-cost and sustainable absorber layer for thin film solar cells (Efficiency: 0.33%, Voc: 226 mV, Isc: 4 mA/cm2, FF: 36.3%).

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