Soluble tetra-methoxyltriphenylamine substituted zinc phthalocyanine as dopant-free hole transporting materials for perovskite solar cells

The development of solution-processed and dopant-free hole transporting materials (HTMs) are important for the future large-scale application of perovskite solar cells (PSCs). Here, a tetra-methoxyltriphenylamine substituted zinc phthalocyanine (OTPA-ZnPc) has been synthesized and utilized as a dopant-free HTM for PSCs. The introduction of 4,4'-dimethoxytriphenylamine side chains on ZnPc possesses a wonderful solubility in various solvents, such as dichloromethane, chlorobenzene, and N,N-dimethylformamide. The optimized devices achieved a power conversion efficiency of 16.23% under AM1.5 G standard conditions. What's more, due to the hydrophobic nature of the OTPA-ZnPc, the solar cells remained about 80% of its initial efficiency after 720 h of storage in ambient air with a humidity of approximately 45% without encapsulation, which is obvious better stability than the spiro-OMeTAD devices. Our results indicate that solution-processable OTPA-ZnPc is an encouraging dopant-free hole transporting material in perovskite solar cells.