Photovoltaic performance enhancement via cocktail co-sensitization of D -A - π -A and D- π -A- π -A dyes in dye-sensitized solar cells

A novel organic dye ( BIM37 ) featured with donor - auxiliary acceptor - pi - acceptor (D - A - pi - A) structure based on an acridine pi - bridge has been designed and synthesized for dye-sensitized solar cells (DSSCs). Unlike the acridine-based D - pi - A - pi - A dyes ( BIM25 and BIM26 ), BIM37 was obtained by inserting an auxiliary acceptor between the donor and pi - bridge units. This modification leads to a significant red shift in the absorption spectrum compared to its counterparts. Thus, the DSSCs based on BIM37 achieved a power conversion efficiency (PCE) of 5.03%, which is higher than that of BIM25 (3.76%) or BIM26 (4.56%). To further improve the photovoltaic performance, the cocktail co-sensitization strategy was applied. In the presence of chenodeoxycholic acid (CDCA) as a co-adsorbent, the cosensitized DSSC based on BIM37 & thorn; BIM26 showed a high efficiency of 6.30%. This performance is superior to individual DSSCs with and without CDCA. The results show that molecular engineering for co-sensitization may be an effective strategy to improve the performance of DSSCs.