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

Abstract

Herein, we report the design and the synthesis of three new D-A type metal-free carbazole based dyes (C<inf>1–3</inf>) 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 C<inf>1–3</inf> on their photovoltaic performances. Further, the photovoltaic performance of C<inf>1–3</inf> was determined along with the standard dye P1 and their PCE values were found to be in the order of P1 (0.047%) > C<inf>2</inf> (0.040%) > C<inf>1</inf> (0.016%) > C<inf>3</inf> (0.001%). Interestingly, the NiO based p-type DSSC fabricated with C<inf>2</inf> carrying electron withdrawing N,N-diethyl thiobarbituric acid displayed V<inf>OC</inf> 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<inf>2</inf> 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. © 2017 Elsevier Ltd