6月26日，国际顶级学术期刊《自然》（Nature）在线报道了华中科技大学武汉光电国家研究中心陈炜-刘宗豪团队题为“Buried interface molecular hybrid for inverted perovskite solar cells”的研究论文。
Trans-perovskite solar cells (PSCs) are the mainstream technology route for the industrialization of PSCs, an emerging photovoltaic technology, due to their advantages of high efficiency and stability, easy mass production and stacking. However, in the field of academic research, the certification efficiency of formal (n-i-p) structured PSCs has been in a relatively leading position before, and there are more scholars who study formal structured cells in the early stage. Until 2023, thanks to the development of self-assembled monolayers (SAMs) hole selective layers (HSLs) and defect passivation strategies, the photoelectric conversion efficiency of trans PSCs exceeds that of formal PSCs. However, commonly used SAMs, such as [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz), are not intrinsically conductive, and the device efficiency is extremely sensitive to the film thickness of SAM molecules. The uncontrolled self-assembly state of the molecule on the substrate and the uneven distribution at the molecular scale will lead to the loss of interfacial charge transport, and the poor surface wettability of Me-4PACz to the perovskite precursor solution will cause a large number of microscopic holes and unsatisfactory crystallization at the submerged interface, which will lead to a large number of submerged interface defects and cause serious interfacial recombination, which is an important reason for further breakthroughs in the efficiency of trans PSCs. These drawbacks, especially when manufacturing large-area devices, will be further amplified.
In order to solve the above problems, the Chen Wei-Liu Zonghao team from Wuhan National Research Center for Optoelectronics, Huazhong University of Science and Technology, innovatively proposed a hybrid strategy of self-assembled single-molecule hybrid at the bottom interface, that is, to introduce triphenylamine monomer (4,4',4''-nitrotriphenylcarboxylic acid (NA)) with a large π conjugated group and symmetric polycarboxyl group in the high-performance self-assembled single-molecule Me-4PACz precursor. By comparing the co-adsorbents such as TA and BA, it is found that the molecular structure of NA as a co-adsorbent is more conducive to enhancing the strong π-π interaction with Me-4PACz, which can better reduce the self-aggregation effect of Me-4PACz ultra-thin films during the deposition process, and induce Me-4PACz molecules to obtain a more uniform distribution at the 2nm scale (Fig. 1), thereby improving the extraction efficiency of photogenerated carriers at the embedded interface of perovskite films. In addition, the results of molecular dynamics simulations show that Me-4PACz is distributed in the nickel oxide/perovskite interface in a flat manner, and its phosphonic acid group and π ring can interact with the nickel oxide substrate, and the π ring of Me-4PACz can passivate the Vpb2+ deep level trap, thereby reducing the non-radiative recombination of the interface. In addition, the presence of polycarboxyl NA monomers effectively improves the wettability of perovskite solutions on Me-4PACz, eliminates the nanopores at the embedded interface, releases the compressive stress of perovskite films, and enhances the crystallinity of perovskite embedded interfaces, which further reduces the concentration of defects at the embedded interface and is conducive to the uniform preparation of large-area perovskite films (Fig. 2).
Figure 1. The self-assembly states of different hybrid HSLs interfaces calculated based on first principles
NA诱导Me-4PACz实现最佳自组装成膜
Figure 2. Differences in perovskite micropore morphology and crystallization quality at the embedded interface of different hybrid HSLs
In summary, the self-assembled single-molecule hybrid hole transport materials have the advantages of super-wetting, uniform distribution at the nanoscale, fast carrier extraction speed, and low non-radiative recombination, which can realize the efficient carrier transport and defect passivation at the submerged interface at the same time, and greatly improve the device performance. The quasi-steady-state certified efficiency of trans-PSCs based on the preferential bandgap FA0.95Cs0.05PbI3 perovskite by an authoritative third-party organization (NPVM) is as high as 26.54% (Fig. 3), which exceeds the previous meter feeding efficiency record (26.1%, NPVM) certified by the same organization. In addition, the good wettability of the new hybrid self-assembled single-molecule material is very conducive to the preparation of large-area devices, and the certification efficiency of 22.74% has been achieved in the micromodule with a pore size area of 11.1 cm2, which is the highest certification efficiency of the trans micromodule in the same period in the world, which proves the scalability of the self-assembled molecular hybrid strategy at the submerged interface and its great application prospect in large-area perovskite modules. The co-adsorbed polycarboxyl monomers enhance the bonding between perovskite and NiO at the embedded interface, which not only improves the efficiency, but also improves the stability of the device. At present, the above research results have been applied for Chinese invention patents (application number: 202410827860.6).
Figure 3. The authoritative certification efficiency of the device exceeds the efficiency record of the same period
Huazhong University of Science and Technology is the first unit to complete the paper, and Dr. Liu Sanwan, Dr. Chen Rui, Master Sun Zhenxing of Huazhong University of Science and Technology, Associate Professor Li Jingbai of Hoffman Institute of Advanced Materials of Shenzhen Polytechnic University, Dr. Xiao Wenshan of Wuhan University of Technology, and Assistant Professor Zhang Yong of Southern University of Science and Technology are the co-first authors. Prof. Wei Chen and Associate Professor Zonghao Liu from Huazhong University of Science and Technology and Prof. Nam-Gyu Park from Sungkyunkwan University in South Korea are the co-corresponding authors. This research work was supported by the National Key R&D Program of the Ministry of Science and Technology, the National Natural Science Foundation of China, the Independent Innovation Research Fund of Huazhong University of Science and Technology, the Natural Science Foundation of Hubei Province, and the Innovation Program of Optics Valley Laboratory.
Paper Links:
https://www.nature.com/articles/s41586-024-07723-3