p-n Heterojunction of Doped Graphene Films Obtained by Pyrolysis of Biomass Precursors

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2015-02, Vol.11 (8), p.970-975
• Main Authors: Latorre-Sánchez, Marcos, Primo, Ana, Atienzar, Pedro, Forneli, Amparo, García, Hermenegildo
• Format: Article
• Language: English
• Subjects: Alginates - chemistry; Biomass; Borates - chemistry; Boron - chemistry; Catalysis; Chitosan; Chitosan - chemistry; doped graphene; Electrons; Esters; Formations; Graphene; graphene films; Graphite - chemistry; Hall effect; Heterojunctions; Microscopy, Electron, Scanning; Migration; Nanostructures - chemistry; Nanotechnology; Nitrogen - chemistry; Optics and Photonics; p-n heterojunctions; Photochemistry; Photocurrent; photocurrents; Photoelectric effect; Pyrolysis; Semiconductors; Spectrum Analysis, Raman; Temperature; Water - chemistry; Xenon
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201402278

Nitrogen‐doped graphene [(N)G] obtained by pyrolysis at 900 °C of nanometric chitosan films exhibits a Hall effect characteristic of n‐type semiconductors. In contrast, boron‐doped graphene [(B)G] obtained by pyrolysis of borate ester of alginate behaves as a p‐type semiconductor based also on the Hall effect. A p–n heterojunction of (B)G‐(N)G films is built by stepwise coating of a quartz plate using a mask. The heterojunction is created by the partial overlapping of the (B)G‐(N)G films. Upon irradiation with a xenon lamp of aqueous solutions of H2PtCl6 and MnCl2 in contact with the heterojunction, preferential electron migration from (B)G to (N)G with preferential location of positive holes on (B)G is established by observation in scanning electron microscopy of the formation of Pt nanoparticles (NP) on (N)G and MnO2 NP on (B)G. The benefits of the heterojunction with respect to the devices having one individual component as a consequence of the electron migration through the p‐n heterojunction are illustrated by measuring the photocurrent in the (B)G‐(N)G heterojunction (180% current enhancement with respect to the dark current) and compared it to the photocurrent of the individual (B)G (15% enhancement) and (N)G (55% enhancement) components. A p–n heterojunction of N‐ and B‐doped graphene [(N)G and (B)G] is prepared by pyrolisis of chitosan and borate‐modified alginate films, respectively, and created by partial overlapping of the films. Preferential electron migration from (B)G to (N)G is established by observation in scanning electron microscopy of the formation of Pt nanoparticles (NP) on (N)G and MnO2 NP on (B)G. The photocurrent of the (B)G‐(N)G heterojunction is clearly enhanced with respect to the individual components.