Improving the stability of solar cells using metal–organic frameworks

Abstract

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 Cu_2−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.