Novel metal-free organic dyes possessing fused heterocyclic structural motifs for efficient molecular photovoltaics

Abstract

Reported herein are six novel metal free organic dyes such as PCA1-PCA3 and PCTA1-PCTA3 featuring fused heterocyclic structural motifs such as phenothiazine and alkylcarbazole. Photophysical/electrochemical properties and nanocrystalline TiO₂ based dye-sensitized solar cell performance of the same have been investigated. Electronic distribution within the molecules has been determined through a computational approach. The overall power conversion efficiencies of the devices with the utilization of dyes PCA1-PCA3 and PCTA1-PCTA3 as sensitizers ranges between 4.67 and 8.08%. The novel dyes possessing cyanoacrylic acid as electron acceptor, PCA1-PCA3, exhibit higher power conversion efficiency, short-circuit current, open-circuit voltage, and electron lifetime those with thioxothiazolidinylacetic acid, PCTA1-PCTA3, as the same. Of the devices fabricated by employing the new metal-free organic sensitizers, that with the dye PCA2 exerted a power conversion efficiency (PCE, η) of 8.08% with a short circuit current density (J_SC) of 16.45 mA cm^-2, an open circuit voltage (V_OC) of 735 mV and a fill factor (ff) of 0.68; this PCE is the highest amongst the devices fabricated.