Regulation of Interface Schottky Barrier and Photoelectric Properties in Carbon-Based HTL-Free Perovskite Solar Cells.

Carbon-based hole transport layer (HTL)-free perovskite solar cells (C-PSCs) receive a lot of attention because of their simplified preparation technology, low price, and good hydrophobicity. However, the Schottky junction formed at the interface between perovskite and carbon poles affects the photogenerated carrier extraction and conversion efficiency. In this paper, 4-trifluoromethyl-2-pyridinecarboxylic acid (TPCA) is used to modify the perovskite films. The introduction of TPCA can reduce the p-type Schottky barrier height (p-SBH) and thin the Schottky barrier width W, which greatly improves the hole transport ability and tunneling probability. Meanwhile, the n-type Schottky barrier height (n-SBH) shows a rising trend, which prevents the reverse electron transport to carbon, suppresses unnecessary carrier complexes, and greatly improves the device's optoelectronic performance. Besides, the pyridine nitrogen and C = O in TPCA interact with Pb to raise the crystal quality of perovskite films while inhibiting nonradiative recombination. The results show that compared with the pristine device's 11.45% photoelectric conversion efficiency （PCE), the TPCA-modified device achieves 13.64% PCE. The device's long-term stability significantly improved post-TPCA modification. After 720 h of storage at room temperature and 40-60% relative humidity in the air, the unencapsulated device retained 77% of its initial efficiency.