Eco-Friendly NaSbS2 Quantum Dot-Sensitized Solar Cells

Abstract

Ternary sulfide NaSbS2 is a low-cost, environmentfriendly semiconductor that has rarely been studied. This paper demonstrates, for the first time, solid-state NaSbS2 quantum dot-sensitized solar cells (QDSSCs). NaSbS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanoparticles were synthesized using the sequential ionic layer adsorption reaction method. Solid-state QDSSCs were fabricated from the synthesized nanoparticles using spiro-OMeTAD as the hole-transporting electrolyte. The best cell yielded an efficiency of 1.27% under 1 sun. At the reduced light intensity I0 of 10% sun, the efficiency increased significantly to 4.11% with an open-circuit voltage Voc of 0.51 V, a short-circuit current density J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> of 1.68 mA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and a fill factor (FF) of 47.8%. A sublinear power law of J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> ∝ I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.52</sup> accounts for the large improvement in performance under low-light intensities because of the reduced carrier recombination. The external quantum efficiency (EQE) spectrum covered the spectral region of 300-750 nm with a maximum EQE value of 72% at λ = 450 nm. The present efficiency (4.11%) represents about 30% improvement over the best previous result (3.18%) of liquid-junction QDSSCs. The respectable efficiency indicates that NaSbS2 shows potential as an efficient solar absorber material.