Multifunctional CNT:TiO2 additives in spiro-OMeTAD layer for highly efficient and stable perovskite solar cells

Hole transport layer (HTL) is very important for the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). As current state-of-the-art HTL, Li-TFSI doped spiro-OMeTAD often suffers low conductivity and the hydrolysis of the additive Li-TFSI, which significantly hinders the further improvement of PCE of PSCs. Besides, conventional spiro-OMeTAD has no functional of directly passivating the perovskite crystal defects. Herein, multifunctional TiO2 nanoparticles (NPs)-modified CNT (CNT:TiO2) doped spiro-OMeTAD (spiro-OMeTAD+CNT:TiO2) HTL is reported for the first time. The incorporated CNT:TiO2 not only significantly increases the conductivity of spiro-OMeTAD+CNT:TiO2, but also effectively passivates the crystal defects of perovskite layer. The optimized PSCs with spiro-OMeTAD+CNT:TiO2 HTL achieved a peak PCE of 21.53%, much higher than that (17.90%) of the conventional spiro-OMeTAD based PSCs and also show significantly improved stability.

Automated summary

The hole transport layer (HTL) is crucial for the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). By incorporating CNT:TiO2, the spiro-OMeTAD+CNT:TiO2 not only enhances conductivity significantly, but also effectively passivates the crystal defects of the perovskite layer. The optimized PSCs with spiro-OMeTAD+CNT:TiO2 HTL achieved a peak PCE of 21.53%, much higher than conventional spiro-OMeTAD based PSCs and showed improved stability.