Cobalt selenide hollow nanorods array with exceptionally high electrocatalytic activity for high-efficiency quasi-solid-state dye-sensitized solar cells

In quasi-solid-state dye-sensitized solar cells (QSDSSCs), electron transport through a random network of catalyst in the counter electrode (CE) and electrolyte diffusion therein are limited by the grain boundaries of catalyst particles , thus diminishing the electrocatalytic performance of CE and the corresponding photovoltaic performance of QSDSSCs. We demonstrate herein an ordered Co 0.85 Se hollow nanorods array film as the Pt-free CE of QSDSSCs. The Co 0.85 Se hollow nanorods array displays excellent electrocatalytic activity for the reduction of I 3 − in the quasi-solid-state electrolyte with extremely low charge transfer resistance at the CE/electrolyte interface, and the diffusion of redox species within the Co 0.85 Se hollow nanorods array CE is pretty fast. The QSDSSC device with the Co 0.85 Se hollow nanorods array CE produces much higher photovoltaic conversion efficiency (8.35%) than that (4.94%) with the Co 0.85 Se randomly packed nanorods CE, against the control device with the Pt CE (7.75%). Moreover, the QSDSSC device based on the Co 0.85 Se hollow nanorods array CE presents good long-term stability with only 4% drop of power conversion efficiency after 1086 h one-sun soaking.