Metal–organic-framework derived porous conducting frameworks for highly efficient quantum dot-sensitized solar cells

Abstract

Metal–organic-framework (MOF) derived carbon materials have attracted particular attention in recent years as a new class of porous conducting materials because of their well-connected networks, and tunable and versatile porosities. Herein, we report on a novel porous MOF-derived carbon framework supported PbS quantum dot-sensitized solar cells (QDSSCs). A zeolitic-imidazole framework (ZIF) layer is prepared by printing ZIF-67 powders, followed by the careful carbonation in N₂. Then nanocrystalline SnO₂ thin film is coated and PbS quantum dots (QDs) are further deposited to form a PbS QD-sensitized porous conducting framework supported nanocrystalline SnO₂ thin film. The morphologies and microstructure of the porous conducting framework were characterized in detail by the measurements of XRD, SEM, TEM, Raman spectrum and BET. Prior to deposition of PbS QDs, a compact TiO₂ layer is modified on the sites of the porous conducting framework uncovered by SnO₂ nanoparticles. The porous conducting framework is beneficial to the electron transporting process in the nanocrystalline thin film, while the compact TiO₂ layer effectively suppresses the recombination of the transported electrons. The photovoltaic performance of QDSSCs is greatly improved due to the introduction of the porous conducting framework and the corresponding TiO₂ compact layer. Eventually, the porous conducting framework buried in the nanocrystalline thin film improves light-to-electric conversion efficiency by 2.5 times compared with that of the cell without the porous carbon framework.