Study of ZnO nanostructures with intentionally introduced defects for photovoltaics and optical gas sensing
Résumé
In the present communication, we propose the application of the wide bandgap semiconductor nanoparticles (NPs) as energy converters for the enhancement of the spectral response of solar cells. Nanoparticles permit to achieve a high concentration of the intermediate energy levels in the bandgap, necessary for an efficient down-shifting (a variant of down-conversion process, in which one high energy photon is converted into one lower-energy photon) and at the same time, they can act as an antireflective layer [1]. Wide band gap semiconductors, such as ZnO, absorb efficiently the UV light in the spectral zone where the efficiency of most solar cells (CdTe, CIGS, amorphous Si) is low and convert it into the visible light at the wavelengths where the solar cell spectral response is higher. Moreover, ZnO specifically turns out be a very attractive material for down-shifting applications, as it is non-harmful and abundant, benefits from cheap and easy fabrication methods, has a wide bandgap (3.4 eV) and a higher absorption coefficient than other wide bandgap materials such as GaN. We first show that the synthesis conditions (hydrolysis or co-precipitation), can be used to control and enhance the visible luminescence of ZnO NPs in order to achieve high quantum photoluminescent yield. The subsequent use of these nanoparticles as a down-shifting material for photovoltaic cells is demonstrated [2]. This visible defect luminescence in ZnO nanostructures and more precisely nanowires turns out to be sensitive to some toxic gases can be applied in the optical gas sensing, especially in the explosive environment, where the resistive gas sensors cannot be applied.
References:
[1] A. Apostoluk, Y. Zhu, B. Masenelli, J.-J. Delaunay, M. Sibiński, K. Znajdek, A. Focsa, I. Kaliszewska, Improvement of the solar cell efficiency by the ZnO nanoparticle layer via the down-shifting effect, Microelectronic Engineering 127, pp. 51–56, 2014, DOI:10.1016/j.mee.2014.04.025
[2] A. Apostoluk, Y. Zhu, B. Canut, B. Masenelli, J.-J. Delaunay, K. Znajdek and M. Sibiński, Investigation of luminescent properties of ZnO nanoparticles for their use as a down-shifting layer on solar cells, Phys. Status Solidi C 10 (10), 1301–1307, 2013; DOI: 10.1002/pssc.201200950