Abstract
By simple soaking titanium dioxide (TiO2) films in an aqueous Na2S solution, we could prepare surface-modified photoanodes for application to dye-sensitized solar cells (DSSCs). An improvement in both the open-circuit voltage (Voc) and the fill factor (FF) was observed in the DSSC with the 5 min-soaked photoanode, compared with those of the control cell without any modification. The UV–visible absorbance spectra, UPS valence band spectra, and dark current measurements revealed that the Na2S modification led to the formation of anions on the TiO2 surface, and thereby shifted the conduction band edge of TiO2 in the negative (upward) direction, inducing an increase of 29 mV in the Voc. It was also found that the increased FF value in the surface-treated device was attributed to an elevation in the shunt resistance.
Highlights
Titanium dioxide (TiO2, titanium (IV) oxide, or titania) has a wide range of applications such as paint, sunscreen, food coloring, photocatalysts, perovskite solar cells, and dye-sensitized solar cells (DSSCs) [1,2]
It has been reported that a surface modification of the TiO2 layer can enhance the open-circuit voltage (Voc ) due to the shift of the conduction band edge (CBE) of the TiO2 arising from the formation of a surface dipole
Since the photoanode modified with the Na S solution for 5 min showed the highest power conversion efficiency (PCE), we focused on this device (Na2 S(5)-TiO2 /FTO) in our investigations of the origin of the efficiency
Summary
Titanium dioxide (TiO2 , titanium (IV) oxide, or titania) has a wide range of applications such as paint, sunscreen, food coloring, photocatalysts, perovskite solar cells, and dye-sensitized solar cells (DSSCs) [1,2]. It has been reported that a surface modification of the TiO2 layer can enhance the open-circuit voltage (Voc ) due to the shift of the conduction band edge (CBE) of the TiO2 arising from the formation of a surface dipole. Molecules 2020, 25, 1502 onto the TiO2 surface shifted the CBE of TiO2 in the negative direction owing to the formation of a surface dipole, leading to an increase in the Voc. in the previous works, the surface modification process using inorganic compounds was time and energy consuming because additional thermal annealing at an elevated temperature should be conducted after dipping TiO2 films in respective solutions of their precursors. We expected the TiO2 surface modification using strong base to alter surface charges in a short processing time, which could increase photovoltaic properties of DSSCs
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
