Preparation of structurally modified, conductivity enhanced-p-CuSCN and its application in dye-sensitized solid-state solar cells

A method is found to significantly improve the p-type conductivity of CuSCN modified by incorporating triethylamine coordinated Cu(II) sites in its structure. It is done by mixing triethylamine hydrothiocyanate with CuSCN in propyl sulfide solution and allowing it to stand still in the dark for a few weeks in a closed sample tube. XRD and SEM analyses point to the modification of the CuSCN material. The Hall effect measurements clearly show a significant enhancement of hole concentration and hence of p-type conductivity. A maximum conductivity of 1.42 S m−1 is achieved for the structurally modified CuSCN compared to that of 0.01 S m−1 for ordinary CuSCN. AC impedance analysis of solid-state dye-sensitized solar cells based on this material clearly shows the reduction of bulk resistance of the cell with the use of modified CuSCN. This decrease in resistance has been attributed to the enhancement of conductivity and better pore filing of modified CuSCN inside the TiO2 matrix. As such, the solar cell performance gradually increases to an optimum value beyond which it decreases. The best result obtained for conversion efficiency is 3.4% at AM 1.5, which is a 41.8% enhancement from the best reported value for a dye-sensitized solid-state solar cell using CuSCN as a hole conducting material. The best efficiency value obtained is 14 times higher than that obtained for the dye-sensitized solid-state solar cell made with ordinary CuSCN.

Structurally modified CuSCN material with enhanced conductivity was prepared by mixing CuSCN with triethylamine hydrothiocyanate in propyl sulfide solution and allowing it to react in the dark for a few weeks. The I–V curves of the FTO/TiO2/N719/CuSCN/Pt-FTO cells prepared using (a) pure CuSCN, (b) 1 day, (c) 10 days, and (d) 20 days of reacting CuSCN with triethyl ammonium thiocyanate in propyl sulfide are shown below.Figure optionsDownload as PowerPoint slideHighlights
► A versatile procedure is developed to enhance the conductivity of CuSCN.
► Conductivity enhancement is observed in Hall measurements and in AC-impedance studies.
► Improved performance is observed when utilizing modified CuSCN materials in DSSCs.