Keggin-Type PMoV as a P-type Dopant for Enhancing the Efficiency and Reproducibility of Perovskite Solar Cells.

The conventional perovskite solar cells (PSCs) with 2,2',7,7'-tetrakis(N,N-dimethoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) as a hole transporting material commonly suffer from poor stability and reproducibility mainly due to the process of placing the devices in air and illumination for oxidizing the spiro-OMeTAD. Herein, Keggin-type polyoxometalates (POMs)-phosphovanadomolybdate (HPMoV·nHO, denoted as PMoV) is for the first time employed as a p-type dopant for promoting the oxidation of spiro-OMeTAD. Thereby, without illumination and air, the conductivity and hole extraction efficiency of the PMoV doped spiro-OMeTAD with assistance of lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and 4-tert-butylpyridine (TBP) can be dramatically enhanced. On the basis of this strategy, the corresponding PSCs exhibit substantially improved photovoltaic performance and good reproducibility. The best performing device yields a power conversion efficiency (PCE) of 14.05%. This work indicates a great potential of polyoxometalates for further applications in solar cells and other optoelectronics devices.