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 easyfabrication 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 V 10(-6) S cm(-1) for the pristine spiro-OMeTAD to 1.1 V 10(-3) S cm(-1) at 5% BPO doping and to 2.4 V 10(-2) S cm(-1) at 15% BPO doping, which considerably outperform the conductivity of 4.62 V 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 CH3NH3PbI3 and thus greatly enhances the charge transfer. The BPO-doped spiroOMeTAD is used in the fabrication of perovskite solar cells, which exhibit enhancement in the power conversion efficiency.