Abstract:
Perovskite solar cells (PSCs) are emerging efficient photovoltaic devices, with record-high
power conversion efficiencies (PCE) of more than 25.5%. However, PSCs exhibit some drawbacks,
such as poor stability upon exposure to moisture or humidity, ultraviolet (UV) radiation
and heat, which in turn limits the device lifetime and performance. In addition, the
introduction of perovskite films comes with associated toxicity, which is a major environmental
concern. Furthermore, the application of titanium dioxide (TiO2) as an electron transport
layer (ETL) and 2,20,7,70-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,90-spirobifluorene
(spiro-OMeTAD) as a hole transport layer (HTL), causes device instability. The wide-bandgap
characteristic of TiO2 introduces charge carrier recombination in the ETL, which, in turn,
impairs device performance. This is, over and above, the high cost of spiro-OMeTAD,
coupled with its multi-step synthetic preparation method. To address the aforementioned
shortcomings, approaches, such as modifying the interfacial architecture, have been
explored by introducing versatile materials between the charge-collecting electrode and the
perovskite active layers. In this regard, perovskite oxides are more appealing due to their
wide bandgap and high electron mobility. However, perovskite oxides have limitations due
to their agglomeration, which causes short-circuits and leakage current, in addition to their
poor charge separation efficiency, surface hydrophilicity and weak visible-light absorption.
As a result, nanocomposites of perovskite oxides with carbon-based materials, particularly
graphene and its derivatives, have attracted significant research attention due to their
exceptional optoelectronic properties, superior stability, and non-toxicity of graphene-based
materials. Therefore, this review discusses the recent trends in graphene-based materials,
their composites with perovskite oxides, effective ETLs or HTLs of PSCs and the subsequent
improvement of photovoltaic performance. In addition, a summary of synthetic routes for
perovskite oxides/graphene nanocomposites is presented. This review will foster the
advancement of the fabrication of PSCs with improved PCE and stability.