Corresponding Author

Yong-fang LI(liyf@iccas.ac.cn)


Organic/inorganic hybrid metal halide perovskite semiconductor materials have drawn great attention for the application in solar cells in recent years because of their combined superior photoelectrical properties of inorganic semiconductors (with high dielectric constant and high charge carriers mobility) and organic semiconductors (with good solution processability and high absorbance). The power conversion efficiency (PCE) of the organometal halide perovskite solar cells (pero-SCs) based on CH3NH3PbI3 has been increased dramatically in a few years from 3.8% to a certified 22.1%, primarily owing to the development of new interfacial materials, careful optimization of morphology, and perovskite crystallization processes of the active layers and the device architecture. Among the optimization strategies, interface engineering plays a vital role in improving photovoltaic performance of the pero-SCs. Organometal halide perovskite material CH3NH3PbI3 was first used in solar cells in 2009 as a sensitizer in dye-sensitized solar cells with a PCE of 3.81%, and then the PCE was improved to 6.54% in 2011. However, the stability of the solar cells with a liquid electrolyte is very poor due to the easy decomposition of the perovskite in the liquid electrolyte. In 2012, spiro-MeOTAD was used as a solid hole transporting layer on the perovskite layer instead of liquid electrolyte, and all solid state pero-SCs were fabricated. The solid state pero-SCs based on mesoporous TiO2 electrode showed higher PCE of 9.7% with much improved stability. Later, the planar structured pero-SCs were developed with the dense planar electrode as a cathode. Now the planar structured pero-SCs can be classified into planar n-i-p pero-SCs with a cathode buffer layer (CBL) on a transparent electrode and p-i-n pero-SCs with an anode buffer layer on a transparent electrode. In this review article, we summarized the latest development of CBLs for highly efficient and stable planar p-i-n pero-SCs. The CBL materials can be divided into inorganic metal oxides, metals or metal salts, and n-type organic semiconductor materials according to the types of materials. And the types of the CBLs can be classified into single CBL, double CBLs, and hybrid CBL according to the CBL composition. The effects of the CBLs on the photovoltaic performance and device stability of the pero-SCs were reviewed systematically. Finally, we summarized the effects of CBL on the improvements of device efficiency and stability as well as the requirements for an ideal CBL. We hope that the properties and requirements of the ideal CBLs we summarized in this article will provide guidance for the future molecular design of cathode interfacial materials.

Graphical Abstract


planar p-i-n perovskite solar cells, cathode buffer layers, efficiency and stability, organic/inorganic hybrid metal halide perovskite semiconductor materials

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