No abstract

We designed and synthesized new alkyl-functionalized organic dyes, MK-1 and MK-2, for dye-sensitized solar cells (DSSCs). Based on the MK-2 dye, a high performance of efficiency (eta, 7.7%; short-circuit current density Jsc = 14.0 mA cm-2, open-circuit voltage Voc = 0.74 V, and fill factor FF = 0.74) was achieved under AM 1.5 G irradiation (100 mW cm-2). Remarkably, the relatively higher Voc for DSSCs based on MK-1 and MK-2 dyes, which have long alkyl chains, were observed among the organic dyes caused by the increasing of the electron lifetime in the conduction band of TiO2. Our molecular design of alkyl-functionalized dyes strongly suggests the promising performance of molecular photovoltaics based on organic dyes.

We present herein a facile one-step low-temperature hydrothermal approach for in situ growth of metal selenides (Co(0.85)Se and Ni(0.85)Se) on conductive glass substrates. The as-prepared metal selenides on conductive substrates can be used directly as transparent counter electrodes for dye-sensitized solar cells (DSSCs) without any post-treatments. It is found that graphene-like Co(0.85)Se exhibits higher electrocatalytic activity than Pt for the reduction of triiodide. As a consequence, the DSSC with Co(0.85)Se generates higher short-circuit photocurrent and power conversion efficiency (9.40%) than that with Pt.

A novel concept "D-A-π -A" organic sensitizer instead of traditional D-π -A ones is proposed. Remarkably, the incorporated low bandgap, strong electronwithdrawing unit of benzothiadiazole shows several favorable characteristics in the areas of light-harvesting and effi ciency: i) optimized energy levels, resulting in a large responsive range of wavelengths into NIR region; ii) a very small blue-shift in the absorption peak on thin TiO 2 fi lms with respect to that in solution; iii) an improvement in the electron distribution of the donor unit to distinctly increase the photo-stability of synthetic intermediates and fi nal sensitizers. The stability and spectral response of indoline dye-based DSSCs are improved by the strong electron-withdrawing benzothiadizole unit in the conjugation bridge. The incident-photon-conversion effi ciency of WS-2 reaches nearly 850 nm with a power conversion effi ciency as high as 8.7% in liquid electrolyte and 6.6% in ionic-liquid electrolyte.