Electrodeposited MoS2 as electrocatalytic counter electrode for quantum dot- and dye-sensitized solar cells

Abstract

Molybdenum disulfide (MoS2) films are electrochemically synthesized on F-doped SnO2 (FTO) substrates using potentiostatic electrodeposition (ED) at a constant -1 V for 20-60 min. The MoS2 is deposited according to island growth mode. As the ED time increases to 40 min, the clusters of MoS2 nano particles enlarge and thicken, but maintain nanopores between the clusters. Additional increase in ED time (to 60 min) causes clusters to merge and make the film denser. Furthermore, this MoS2 film exhibits cracks due to stress accumulated in the film. The film FTO/MoS2 (40 min) shows significantly enhanced electrocatalytic activity compared to other films. This is because the FTO/MoS2 (40 min) not only has more electrochemically active sites but also significantly facilitates charge transfer and mass transport. When it is employed as the counter electrode (CE) for quantum-dot and dye-sensitized solar cells (QD-SSC, D-SSC), the QD-SSC with FTO/MoS2 (40 min) CE exhibits even higher overall energy conversion cell efficiency (3.69%) than that with Pt CE (2.16%). Moreover, the D-SSC with FTO/MoS2 (40 min) CE exhibits cell efficiency (7.16%) similar to that with FTO/Pt CE (7.48%). This indicates that MoS2 is a promising CE for all QD-SSCs and D-SSCs. © 2017 Elsevier Ltd.