The carrier transport layer is the core component of perovskite solar cell (PSC). The carrier transport layer can timely and effectively separate photogenerated electrons and transport them to the electrodes, and at the same time block the transport of photogenerated holes, reduce the recombination of carriers at the interface, and help improve the transfer efficiency of charges. In order to further improve the conductivity of the carrier transport layer and suppress the charge recombination ability, the ability of the carrier transport layer can be improved by adding additives. Common additives include tetra-tertbutyl pyridines (TBPs), imidazole ionic liquids, lithium (Li) complexes, cobalt (Co) complexes, etc. Additives with good performance should be non-toxic, non-volatile, stable in performance, can improve the electrical properties of carrier transport materials, and can inhibit charge recombination.
Figure 1. Chemical structures of some carrier transport layer additives
- Perovskite Solar Cell (PSC): The carrier transport layer of PSC is divided into a hole transport layer and an electron transport layer. The carrier mobility and energy level structure of the carrier transport layer directly determine the efficiency and balance of carrier injection and the blocking effect on reverse carriers, which play a crucial role in the photoelectric conversion efficiency of PSCs. The carrier transport layer often improves its own properties by adjusting the preparation parameters, such as structure crystal plane, doping elements, introducing additives and so on. Among them, the control strategy of introducing additives can conveniently and efficiently prepare the carrier transport layer without adjusting the manufacturing process and instruments. Adding carrier transport layer additives to the carrier transport layer can slow down the nucleation process of the material and improve the grain size. In some cases, carrier transport layer additives can act as "carrier bridges", accelerating charge transfer and thus reducing recombination. As an important substance to improve PSC efficiency, carrier transport layer additives can optimize the performance of PSC devices and expand application fields.
- Lujie Yin, Yingtao Li, Xincheng Yao, Yanzhou Wang, Lin Jia, Qiming Liu, Junshuai Li, Yali Li, Deyan H. MXenes for Solar Cells [J]. Nano-Micro Letters, 2021, 13, 78.