Graphene dispersion as a passivation layer for the enhancement of perovskite solar cell stability

Stability issues in perovskite solar cells (PSCs) is never declined despite that the efficiency of current PSCs impressively improved. In this work, graphene, the most stable carbon material, was used in enhancing the stability of PSCs. A facile route was provided, wherein graphene was dispersed in isopropanol and then deposited on top of a hole transport layer through the spin-coating technique. The graphene layer acts as a passivation layer in PSCs by protecting interlayer perovskite/hole transport layer (HTL) from oxygen and moisture ingress. Different concentrations of the graphene dispersion (0.6, 0.8, 1.0, 5.0 and 10.0 mg/ml) were used in exploring the function of the graphene layer as the passivation layer and its role in preventing PSC deterioration due to photo-oxidation, moisture or chemicals. Raman intensities of the graphene layer were directly proportional to concentrations. Graphene dispersion layer concentrations at 5.0 and 10.0 mg/ml improved the stability of PSCs by approximately 90% within 60 h, with the efficient performance of 5.3% and 3.9%, respectively. Comprehensive studies of morphology support these results, and optical and electrical properties showed the correlation between the features.