Highly efficient CH₃NH₃PbI₃ perovskite solar cells prepared by AuCl₃-doped graphene transparent conducting electrodes

We employed AuCl₃-doped graphene as a p-type transparent conducting electrode (TCE) in an p-i-n type CH₃NH₃PbI₃ perovskite solar cell using poly (3,4-ethylenedioxythiophene):poly(styrene sulfonate) and phenyl-C61-butyric acid methyl ester as the hole and electron transporting layers, respectively, and obtained 17.4–17.9% power conversion efficiency at 1 Sun condition. The work function of the AuCl₃-doped graphene TCE was controllable from ∼4.52 to ∼4.86 eV. Due to the p-type doping by the AuCl₃ treatment, the graphene TCE shows good hole mobility and greatly-improved sheet resistance (∼70 ohm/cm²) compared to the pristine graphene TCE (∼890 ohm/cm²) but its transmittance was gradually decreased with the doping concentration (n_D). Owing to the trade-off correlation between the sheet resistance and the transmittance of the AuCl₃-doped graphene TCE, the ratio of DC conductivity and optical conductivity was the highest at n_D = 7.5 mM. Therefore, the highest performance was achievable by using 7.5 mM AuCl₃-doped graphene TCE.