Introducing an alternative oxidant for Spiro-OMeTAD with the reduction product to passivate perovskite defects

Spiro-OMeTAD has been playing an indispensable role in highly efficient perovskite solar cells (PSCs). However, a long air oxidation process is usually required, which is harmful to the device stability. Herein, a simple and efficient doping strategy is proposed by adding a low-cost organic oxidant (2-iodoxybenzoic acid, IBX) to spiro-OMeTAD. IBX can accelerate the oxidation process of spiro-OMeTAD, thus effectively improving the conductivity and hole mobility of hole transport layers. What's more interesting, it is found that the reduction product of IBX, 2-iodobenzoic acid, can passivate the I vacancies and uncoordinated Pb 2+ defects on the surface of perovskite, thereby inhibiting nonradiative recombination. Ultimately, the IBX-treated PSCs achieved a power conversion efficiency of 22.45%, superior to that of the pristine device (20.42%). In addition, the stability of the IBX-based device is improved. Overall, the cost-effective, facile and dual functional doping strategy is quite promising in improving the efficiency and stability of PSCs. A low-cost organic oxidant IBX is used to oxidize spiro-OMeTAD. Moreover, the reduction product of IBX can passivate defects, and inhibit nonradiative recombination. The IBX-treated PSCs achieved a high efficiency of 22.45% with improved stability.