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 degrees 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.