Recently, the research group led by Dr. Hou Fuhua from the School of Physical Science and Technology at our university has made the latest progress in controlling the buried bottom interface of inverted perovskite solar cells based on nickel oxide. The research findings, titled “Dipropyl sulfide optimized buried interface to improve the performance of inverted perovskite solar cells”, were published in the excellent journal Applied Physics Letters (Nature Index Inclusion). The link to the paper is: https://doi.org/10.1063/5.0226220

[4- (3,6-dimethyl-9H-carbazol-9-yl) butyl] phosphate (Me-4PACz) has been proven to be a highly effective NiOx surface passivation material for enhancing the photoelectric conversion efficiency of inverted perovskite solar cells with NiOx as the hole transport layer. However, the hydrophilicity of the Me-4PACz passivation layer is poor, which cannot uniformly cover NiOx and is not conducive to the uniform deposition of subsequent perovskite films. The hydroxyl radicals and high valence Ni ions present on the surface of NiOx thin films come into contact with perovskite thin films, leading to a decrease in device stability.

This paper uses dipropyl sulfide (DPS) to dope Me-4PACz in isopropanol (IPA) solution. Firstly, doping DPS can reduce the molecular aggregation phenomenon of Me-4PACz and improve the interfacial contact performance of Me-4PACz/NiOx. By calculating the differential lifetime of perovskite films on different substrates, it is demonstrated that the improved device has better hole extraction efficiency and higher crystalline quality of perovskite films. Then, X-ray photoelectron spectroscopy further revealed the reaction between DPS and hydroxyl groups on the surface of NiOx, and reduced the high valence Ni4+. The deprotonation reaction of A-site cation and the oxidation of I - are inhibited, effectively suppressing the degradation of perovskite layer. In addition, UV photoelectron spectroscopy tests on the hole transport layer indicate that the decrease in valence band energy is attributed to the increase in Ni3+content, which makes the valence band energy levels between the hole transport layer and the perovskite layer more matched, promoting the transport of hole carriers. Finally, the improved device was further calculated to have a lower recombination coefficient and reduced non radiative recombination loss based on transient photovoltaic data under different polarizations. The results indicate that the improvement of the buried interface of DPS can simultaneously enhance the photoelectric conversion efficiency and stability of the device.

This study was supported by projects such as the National Natural Science Foundation of China, the Central Leading Local Science and Technology Development Fund Project, the Key Science and Technology Project of Higher Education Institutions in Inner Mongolia Autonomous Region, the Research Support Project for Introducing High level Talents at the Inner Mongolia Autonomous Region Level, and the High-level Talent Introduction Project of Inner Mongolia University's Steed Plan. In this work, Researcher Hou Fuhua is the sole corresponding author, our research group's 2022 master's student Wei Jiali is the first author, and Inner Mongolia University is the sole completion unit.