Author details

Ulises Antonio Méndez Romero<sup>1</sup> , Miguel Ángel Velasco Soto<sup>1</sup> , Liliana Licea Jiménez1,2, Jaime Álvarez Quintana1,2 and Sergio Alfonso Pérez García1,2\*

\*Address all correspondence to: alfonso.perez@cimav.edu.mx

1 Center for Advanced Materials Research S.C. (CIMAV), Unidad Monterrey, Apodaca, NL, Mexico

2 GENES—Group of Embedded Nanomaterials for Energy Scavenging, Apodaca, NL, Mexico

#### References

A process to decrease the band gap, by means, reducing the oxygen content in graphene oxide, i.e. rGO, was established. GO was synthesized through a modified Hummers method, and it has been found that NH4OH, glucose, fructose, and ascorbic acid at pH 10 can be used to modify the band gap. The XPS C1s and UV-vis spectra indicate the gradual elimination of oxygen groups and restitution of graphitic structure, ensuing to a decreased value of band

Ascorbic acid at pH 10 is more effective and fast for sp<sup>2</sup> restitution, resulting in an optical band gap of 1.55 eV. The chemical reduction by fructose and glucose at pH 10 is slower which could be preferred in order to have a more precise control of band gap, but the total sp<sup>2</sup> restoration is lower than that achieved by the ascorbic acid, nevertheless, it has the lowest band gap 1.15 eV

For application in organic solar cells, low band gaps are important because the PCE depends strongly on the effective generation, diffusion, and dissociation of the exciton. Because most of the solar energy is in the visible spectrum, a band gap in these values means more absorption of light and hence more exciton generation. Another aspect to consider is that restitution of sp<sup>2</sup> domains entails a better exciton diffusion, because of the high carrier mobility. Finally, considering the band gap as the energy difference between the HOMO and LUMO, a low value is advantageous because the difference of the LUMOs, both in the acceptor and donor molecules or polymers, must be adequate for the exciton bonding dissociation and therefore increase

The authors are beholden for the technical support and facilities at CIMAV Monterrey, as well as to the Mexican National Research Council CONACyT for the scholarship of the students involved in this work. Lilia Magdalena Bautista Carrillo and Luis Gerardo Silva Vidaurri for

, Miguel Ángel Velasco Soto<sup>1</sup>

1 Center for Advanced Materials Research S.C. (CIMAV), Unidad Monterrey, Apodaca, NL,

2 GENES—Group of Embedded Nanomaterials for Energy Scavenging, Apodaca, NL,

, Liliana Licea Jiménez1,2,

UV–Vis spectra and XPS spectra, respectively, are also acknowledged.

Jaime Álvarez Quintana1,2 and Sergio Alfonso Pérez García1,2\*

\*Address all correspondence to: alfonso.perez@cimav.edu.mx

gap.

the PCE.

with fructose at pH 10.

94 Graphene Materials - Structure, Properties and Modifications

Acknowledgements

Author details

Mexico

Mexico

Ulises Antonio Méndez Romero<sup>1</sup>

