Simultaneously Modifying Hole Transport Material and Perovskite via a Crown Ether-Based Semiconductor Toward Efficient and Stable Perovskite Solar Cells

In conventional (n-i-p) perovskite solar cells (PSCs), spiro-OMeTAD is the most widely used hole-transporting material (HTM), which contributes to the current state-of-the-art efficiency. Suffering from the low conductivity, dopants such as LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) and tBP are usually required to achieve excellent hole transport properties in spiro-OMeTAD. Nevertheless, the hygroscopicity and the migration of Li+ during device operation severely affect the device's stability. To address the aforementioned issue, a 12-crown-4-based organic semiconductor (CDT) is synthesized and applied in PSCs. Notably, CDT is simultaneously doped in spiro-OMeTAD and perovskite layer through the antisolvent method. In this way, the strong "host-guest" interaction between crown ether and Li+ effectively inhibits its migration both in the hole transporting layer (HTL) and at the perovskite/HTM interface. Furthermore, the carbazole diphenylamine group in CDT facilitates hole transport, and meanwhile improves the hydrophobicity of the HTL. In addition, CDT added into the perovskite layer is also able to passivate defects by interacting with the undercoordinated Pb2+. In light of the aforementioned advantages, the CDT-based device shows a high power conversion efficiency approaching 23%, with excellent long-term stability.