Nanomaterials applied to Optoelectronics and photovoltaic applications

Cu₃N has been introduced as a new class of materials for new generation photovoltaic and photocatalysts applications due to its high absorption light, good electrical properties, high potential realization of p-n homojunctions and highly defect-tolerant semiconductor. The most attractive characteristic feature of Cu₃N is its indirect band gap energy ad its optical absorption coefficient, which is ideal for highly efficient delivery and separation of photo-generated carriers. The transition metal nitrides can reduce the overpotential or activation energy for photocatalytic reactions on the surface of semiconductors by providing extra active sites, and promote the electron–hole separation. However, concerning improve the photocatalytic efficiency, a lot of modifications studies have been done in order to broaden the wavelength range of light that effectively functions, improve the separation of excited charges, and inhibit the recombination of photogenerated carriers.

We are investigating potential carbon based hybrid nanocomposites to produce photocurrent under visible light and UV light excitation. Our recent investigations have shown that it is possible to obtain photocurrent production by combining HfO₂ nanoparticles with multi-walled carbon nanotubes. The other nanoparticles coupled with CNT are ZnO and Ag nanoparticles. Both HfO₂ and ZnO when combined with CNT produce a photocurrent however, the origin of these photo-generated charges are quite different as one is a dielectric while the other is a wide band gap semiconductor. In both cases surface defects play an important role is photocurrent generation.

List of relevant publications:

• “ Fabrication and evaluation of figures of merit of ZnO polymer-based hybrid UV photodiodes “
• “Surface-defect tailoring in SnO₂ (CNT) nanomaterials via sol-gel routes and its influence on the cycling stability“
• “Functional Nanomaterials for Optoelectronics and Photocatalysis (Editorial)”
• “Relevance of alcoholic solvents in the growth of ZnO nanoparticles and ZnO hierarchical nanorod structures on their optical and opto-electrical properties“
• “Revealing the Dependency of Dye Adsorption and Photocatalytic Activity of ZnO Nanoparticles on Their Morphology and Defect States“
• “Tailoring SnO₂ Defect States and Structure: Reviewing Bottom-Up Approaches to Control Size, Morphology, Electronic and Electrochemical Properties for Application in Batteries“
• “Significance of Hydroxyl Groups on the Optical Properties of ZnO Nanoparticles Combined with CNT and PEDOT:PSS“
• “Surveying the Synthesis, Optical Properties and Photocatalytic Activity of Cu₃N Nanomaterials“
• The role of CNT in surface defect passivation and UV emission intensification of ZnO nanoparticles
• “Assessment of the optical and electrical properties of light emitting diodes containing carbon-based nanostructures and plasmonic nanoparticles: a review“

Research project partially funded by the Estonian Centre of Excellence 2015 EQUiTANT (TK134), and EMÜ Bridge Funding (P200030VLVB) .