N-Aryl Arenedicarboximides as Tunable Panchromatic Dyes for Molecular Solar Cells

Zhi Cao,Michael D Heagy,Adriana Penuela,Stephanie Nance,Premchendar Nandhikonda

doi:10.1155/2010/264643

Abstract

Three organic dyes designed as molecular dyads were prepared that feature a common naphthalimide acceptor andN-aryl donors. One of these incorporated an additional cyanoacrylic acid linker and conjugated thiophene bridge inserted between donor and acceptor groups. Electrochemical and photochemical characterizations have been carried out on nanocrystalline TiO2dye-sensitized solar cells which were fabricated with these dyes as the sensitizing component. HOMO and LUMO energies were also calculated using TDDFT methods and validated by the cyclic voltammetry method. A key finding from this study indicates that computational methods can provide energy values in close agreement to experimental for theN-aryl-naphthalimide system. Relative to HOMO/LUMO energy levels ofN719, the dyes based on naphthalimide chromophore are promising candidates for metal-free DSSCs.

Highlights

Among the PV technologies, dye-sensitized solar cells (DSSCs) represent a promising one because of both their high performance as unconventional solar cells and possibility for low-cost production
We report three novel organic dyes with structures shown in Figure 1: (1) containing naphthalimide ring as electron acceptor and methoxyphenyl moiety as electron donor connected to each other without linker; (2) containing naphthalimide ring as electron acceptor and aminophenyl moiety as electron donor connected to each other without linker; (3) containing naphthalimide ring as the electron donor and cyanoacrylic acid as the electron acceptor bridged by a thiophene unit to form a more conjugated system with higher stability
The short wave absorption band corresponds to the π-π∗ transition and the long wave band to an intramolecular charge-transfer (ICT) transition between the aryl donor group and the N.I. acceptor block

Summary

Introduction

Among the PV technologies, dye-sensitized solar cells (DSSCs) represent a promising one because of both their high performance as unconventional solar cells and possibility for low-cost production. The injection of electrons from the sensitizer conduction band to that of TiO2 leads to efficient charge separation, minimizing the electron-hole recombination By noticing these concerns, a key design concept that has been recently discovered is the use of donor/acceptor systems that promote the asymmetric induction of electrons resulting from photoexcited states toward the titanium oxide surface for enhanced PV efficiency [31]. Hattori et al recently reported BODIPY dyes for DSSC applications with Ered values of −1.11 V [40], while for N[(3- and 4-Diarylamino) phenyl]-1,8-Naphthalimide Dyads, the Ered values are more negative, between the range of −1.7 V and −1.8 V [31] This redox potential falls within the preferred voltage required for efficient electron transfer from dye to metal oxide, because it is lower than that of the conduction band of TiO2 at −0.5 V. To gain an insight into the nature of the excited states of N.I dyes, we performed TDDFT calculations on our models

Experimental

Results and Discussion

Conclusion