Molecular simulation of chlorophyll-a derivatives for biological pigment solar cells

ABSTRACT

In this study, various factors affecting the photon-to-electron conversion efficiency of chlorophyll-a derivatives were determined to improve the performance of biological pigment solar cells. By employing the density functional theory with hybrid exchange–correlation functional B3LYP, we calculated the photoelectronic properties such as energy gaps, main transmission path, electronegativity, proton affinity, spectral absorption, and electron transfer rates of chlorophyll-a derivatives, e.g. chlorin–Fe, chlorin–Mg, chlorin–Ni, and chlorin–Zn. The difference in electronegativity between the central metal and the adjacent nitrogen atoms induced changes in the distribution of electron clouds, which indirectly enhanced the absorbance in ultraviolet and long wavelength ranges; thus, the absorption spectrum can be controlled. Further, chlorin–Mg and chlorin–Ni demonstrated better electron transfer rates. The results indicate that design strategies of biopigment derivatives are an effective way to reduce the reorganisation energy, hence improving the electron mobility.

KEYWORDS:

• Chlorophyll-a derivatives
• density functional theory
• electron transfer

Acknowledgements

The authors wish to thank the National Center for High-performance Computing (NCHC) for providing computer facilities and software.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors gratefully acknowledge the financial support from the National Science Council of Taiwan under the contract NSC 98–2221-E–007–108–MY3.