Abstract:
Nowadays, the power conversion efficiency of organometallic mixed halide perovskite
solar cells (PSCs) is beyond 25%. To fabricate highly efficient and stable PSCs, the
performance of metal oxide charge transport layers (CTLs) is one of the key factors.
The CTLs are employed in PSCs to separate the electrons and holes generated in
the perovskite active layer, suppressing the charge recombination rate so that the
charge collection efficiency can be increased at their respective electrodes. In general,
engineering of metal oxide electron transport layers (ETLs) is found to be dominated
in the research community to boost the performance of PSCs due to the resilient
features of ETLs such as excellent electronic properties, high resistance to thermal
temperature and moisture, ensuring good device stability as well as their high versatility
in material preparation. The metal oxide hole transport layers in PSCs are recently
intensively studied. The performance of PSCs is found to be very promising by using
optimized hole transport materials. This review concisely discusses the evolution of
some prevalent metal oxide charge transport materials (CTMs) including TiO2, SnO2,
and NiOx, which are able to yield high-performance PSCs. The article begins with
introducing the development trend of PSCs using different types of CTLs, pointing
out the important criteria for metal oxides being effective CTLs, and then a variety of
preparation methods for CTLs as employed by the community for high-performance
PSCs are discussed. Finally, the challenges and prospects for future research direction
toward scalable metal oxide CTM-based PSCs are delineated.