Benzoyl Peroxide as an Efficient Dopant for Spiro-OMeTAD in Perovskite Solar Cells

Although organic small molecule spiro-OMeTAD is widely used as a hole-transport material in perovskite solar cells, its limited electric conductivity poses a bottleneck in the efficiency improvement of perovskite solar cells. Here, a low-cost and easy-fabrication technique is developed to enhance the conductivity and hole-extraction ability of spiro-OMeTAD by doping it with commercially available benzoyl peroxide (BPO). The experimental results show that the conductivity increases several orders of magnitude, from 6.2×10^-6  S cm^-1 for the pristine spiro-OMeTAD to 1.1×10^-3  S cm^-1 at 5 % BPO doping and to 2.4×10^-2  S cm^-1 at 15 % BPO doping, which considerably outperform the conductivity of 4.62×10^-4  S cm^-1 for the currently used oxygen-doped spiro-OMeTAD. The fluorescence spectra suggest that the BPO-doped spiro-OMeTAD-OMeTAD layer is able to efficiently extract holes from CH₃ NH₃ PbI₃ and thus greatly enhances the charge transfer. The BPO-doped spiro-OMeTAD is used in the fabrication of perovskite solar cells, which exhibit enhancement in the power conversion efficiency.