M. Tomakin

Improving the stability of solar cells using metal–organic frameworks

Although Cu2S-containing chalcogenide solar cells are appealing and cost-effective for photovoltaics (PVs), these materials suffer from rapid performance degradation as a result of the diffusion of copper ions into the CdS layer. In order to prevent this degradation, we report, for the first time, the use of metal–organic frameworks (MOFs) as copper sources. MOFs are a unique class of materials for use in solar cells as they can be tailored to have high porosity in combination with a high density of Lewis basic sites incorporated within the framework backbone. These properties allow for post-metalation reactions to be carried out, which can be exploited for use as copper reservoirs. Experimental evidence shows that the Lewis-basic sites of bipyridine moieties can store copper(I) ions and these ions can be used to compensate for the diffused copper ions leading to an improvement in the stability of prepared Cu2−xS/CdS PV cells. This achievement can ultimately lead to the fabrication of low-cost, long-lived Cu-containing PV cells by using MOFs as supporting materials.

Role of Mg doping in the structural, optical, and electrical characteristics of ZnO-based DSSCs

ZnOand Mg-doped ZnO samples are prepared by spray pyrolysis on conducting glass substrates to fabricate ZnO-based dye-sensitized solar cells (DSSCs). Influences of Mg-doping content on the power conversion efficiencies of ZnO-based DSSCs are investigated. X-ray diffraction results show that all the samples exhibit a hexagonal wurtzite structure. Scanning electron microscopy data indicate that the ZnO sample has uniform rods with 1 μm diameter. With respect to ZnO, the band gap value of 4 at.% Mg-doped ZnO samples improves to the value of 3.27 eV and a further increase in Mg level up to 6 at.% gives rise to a decline in the band gap value of 3.22 eV. Photoluminescence measurements illustrate that intensities of the ultraviolet peak and a red luminescence peak take their maximum values for 4 at.% Mg doping. From solar cell performance measurements, the best power conversion efficiency of 0.08% is obtained for the doping amount of 4 at.% Mg.