RESUMO
To generate and deliver alternative sustainable energy in the face of the current energy crisis, new materials that can capture solar energy and transform it into other useful energies are required. Rare-earth (RE) oxychalcogenides are now being used more frequently as up/down-conversion materials in established photovoltaic (PV) devices to boost their PV performance. Here, through an efficient microwave assisted synthesis procedure, novel nanoplate/sheet shaped nanomaterials of yttrium oxyselenide (YOSe) and its analogues doped with Tb and Eu (YOSe:Tb and YOSe:Eu) were successfully synthesized. Analyses of the structure, stability, morphology, light absorption, and electrochemistry were performed. This work showed that the parent YOSe exhibited green (543 nm) and red (615 nm) emission luminescence when doped with Tb and Eu with a luminescence quantum yield (LQY) of 0.56 and 0.53 for YOSe:Tb and YOSe:Eu nanomaterials, respectively. The surface and material conductivity of YOSe improved with the addition of the dopant elements, with the best outcome shown in YOSe:Eu, according to electrokinetic research evidenced by the enhanced current peaks, reduced charge-transfer resistance (Rct) and low impedance magnitude (Zmag) through electrochemical experiments. These improvements were induced by the distinctive properties of the dopant elements. PCEs of 0.25%, 0.67%, and 1.20% were obtained for YOSe, YOSe:Tb, and YOSe:Eu-based PV devices, respectively, using the nanomaterials as novel absorber layers in a superstrate device design. Our results can initiate further exploitation of the doped host structure for effective down-conversion NIR luminescence for applications in PV devices and to boost the PV performance of existing solar cells.
RESUMO
Metal chalcogenides such as copper zinc tin sulfide (CZTS) have been intensively studied as potential photovoltaic cell materials, but their viability have been marred by crystal defects and low open circuit potential (Voc) deficit, which affected their energy conversion efficiency. Strategies to improve on the properties of this material such as alloying with other elements have been explored and have yielded promising results. Here, we report the synthesis of CZTS and the partial substitution of S with Te via anion hot injection synthesis method to form a solid solution of a novel kesterite nanomaterial, namely, copper zinc tin sulfide telluride (CZTSTe). Particle-size analyzed via small angle X-ray scattering spectroscopy (SAXS) confirmed that CZTS and CZTSTe materials are nanostructured. Crystal planes values of 112, 200, 220 and 312 corresponding to the kesterite phase with tetragonal modification were revealed by the X-ray diffraction (XRD) spectroscopic analysis of CZTS and CZTSTe. The Raman spectroscopy confirmed the shifts at 281 cm-1 and 347 cm-1 for CZTS, and 124 cm-1, 149 cm-1 and 318 cm-1 for CZTSTe. High degradation rate and the production of hot electrons are very detrimental to the lifespan of photovoltaic cell (PVC) devices, and thus it is important to have PVC absorber layer materials that are thermally stable. Thermogravimetric analysis (TGA) analysis indicated a 10% improvement in the thermal stability of CZTSTe compared to CZTS at 650 °C. With improved electrical conductivity, low charge transfer resistance (Rct) and absorption in the visible region with a low bandgap energy (Eg) of 1.54 eV, the novel CZTSTe nanomaterials displayed favorable properties for photovoltaics application.
