Exploring the application of new carbazole based dyes as effective p-type photosensitizers in dye-sensitized solar cells

Herein, we report the design and the synthesis of three new D-A type metal-free carbazole based dyes (C1-3) as effective photosensitizers for p-type DSSCs. in this new design, the electron rich carboxy substituted carbazole unit has been attached to three different electron withdrawing species, viz. N,N-dimethyl barbituric acid, N,N-diethyl thiobarbituric acid and N-ethyl rhodanine. They were well-characterized by spectral, photophysical and electrochemical analyses. Further, their optical and electrochemical parameters along with molecular geometries, optimized from DFT have been employed to apprehend the effect of structures of C1-3 on their photovoltaic performances. Further, the photovoltaic performance of C1-3 was determined along with the standard dye P1 and their PCE values were found to be in the order of P1 (0.047%) > C-2 (0.040%) > C-1 (0.016%) > C-3 (0.001%). Interestingly, the NiO based p-type DSSC fabricated with C-2 carrying electron withdrawing N,N-diethyl thiobarbituric acid displayed V-oc as 59 +/- 4 mV and FF as 29 +/- 1%, which are higher than that of benchmark reference P1. This is attributed to the highest light harvesting ability, the greatest regeneration driving force and the lowest interfacial charge recombination of C-2 among the tested dyes. Conclusively, the results showcase the potential of carbazole based D-A type sensitizers in the development of efficient p-type DSSCs.