Synergistic effect of charge separation and defect passivation using zinc porphyrin dye incorporation for efficient and stable perovskite solar cells†
Organic–inorganic perovskite solar cells (PSCs) suffer from massive ionic defects within perovskite layers, which are regarded as one of the major sources for charge recombination. Herein, a zinc porphyrin dye, YD2-o-C8, is utilized to fabricate high-quality perovskite films with enhanced film crystallinity and uniform morphology. We find that the YD2-o-C8 molecules with carboxylate groups are able to anchor with under-coordinated Pb2+ defects in the perovskite films which would suppress charge recombination. Moreover, perovskites with YD2-o-C8 form an appropriate energy level alignment which is found to be beneficial for both charge separation and extraction in n–i–p devices. Due to these improvements, the best performing device with YD2-o-C8 shows a PCE of 20.5% with reduced hysteresis, while the unmodified devices show a champion efficiency of 18.5%. Unencapsulated PSCs with YD2-o-C8 exhibit better ambient stability, retaining 93% of their initial PCE after storage in ambient air (25–40 °C, 20–40% relative humidity) under dark conditions for 30 days. Our findings present an effective method for defect passivation in perovskite solar cells using mature, low-cost dye molecules which would be favorable for future scale-up fabrication.