Organic D‐A‐π‐A Solar Cell Sensitizers with Improved Stability and Spectral Response

Abstract A novel concept “D‐A‐π‐A” organic sensitizer instead of traditional D‐π‐A ones is proposed. Remarkably, the incorporated low bandgap, strong electron‐withdrawing unit of benzothiadiazole shows several favorable characteristics in the areas of light‐harvesting and efficiency: 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 films 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 final 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 efficiency of WS‐2 reaches nearly 850 nm with a power conversion efficiency as high as 8.7% in liquid electrolyte and 6.6% in ionic‐liquid electrolyte.