Marked Passivation Effect of Naphthalene‐1,8‐Dicarboximides in High‐Performance Perovskite Solar Cells

Abstract

As game‐changers in the photovoltaic community, perovskite solar cells are making unprecedented progress while still facing grand challenges such as improving lifetime without impairing efficiency. Herein, two structurally alike polyaromatic molecules based on naphthalene‐1,8‐dicarboximide (NMI) and perylene‐3,4‐dicarboximide (PMI) with different molecular dipoles are applied to tackle this issue. Contrasting the electronically pull–pull cyanide‐substituted PMI (9CN‐PMI) with only Lewis‐base groups, the push–pull 4‐hydroxybiphenyl‐substituted NMI (4OH‐NMI) with both protonic and Lewis‐base groups can provide better chemical passivation for both shallow‐ and deep‐level defects. Moreover, combined theoretical and experimental studies show that the 4OH‐NMI can bind more firmly with perovskite and the polyaromatic backbones create benign midgap states in the excited perovskite to suppress the damage by superoxide anions (energetic passivation). The polar and protonic nature of 4OH‐NMI facilitates band alignment and regulates the viscosity of the precursor solution for thicker perovskite films with better morphology. Consequently, the 4OH‐NMI‐passivated perovskite films exhibit reduced grain boundaries and nearly three‐times lower defect density, boosting the device efficiency to 23.7%. A more effective design of the passivator for perovskites with multi‐passivation mechanisms is provided in this study.

Indigo: A Natural Molecular Passivator for Efficient Perovskite Solar Cells

“…Among these strategies, antisolution treatments using functional passivating agents such as organic molecules, [23] polymers, [35] and inorganic nanocrystals [36] have been reported to effectively optimize the crystallization process as well as passivate the defects at surfaces and grain boundaries. In general, most effective passivator molecules contain isolated electron pairs isolated electron pairs in molecules framework (Lewis base groups [38] ), such as carbonyl (C=O), [26] sulfoxide (S=O), [37] phosphate (P=O), [20] and cyano (CN). [39] Therefore, the passivating mechanism is interaction between passivating agent (Lewis bases) with positively charged intrinsic site defects on the surface of perovskite (Lewis acids).…”

A dopant-free hole transport material boosting the performance of inverted methylamine-free perovskite solar cells

“…The interaction between PFDTS and In of ITO causes electron donation from PFDTS to the In atoms of ITO, therefore the In 3d peaks shift to lower binding energies. 38 The high-resolution Sn 3d core-level spectra of ITO, ITO/PTAA and ITO/PFDTS are shown in Fig. 3b.…”

In Situ Graded Passivation via Porphyrin Derivative with Enhanced Photovoltage and Fill Factor in Perovskite Solar Cells

“…For the pure perovskite film without ZnPP treatment, there are two main Pb 4 f peaks located at 138.48 and 143.39 eV, corresponding to the Pb 4 f 7/2 and Pb 4 f 5/2 , respectively, and two small peaks at lower binding energy being related to the metallic Pb 0 which is generally believed to be strongly tied to the defects (Figure 1f). [ 35 ] After embedding ZnPP into the perovskite films, the Pb 4 f signals shifted to lower binding energies (BEs) of 138.34 and 143.24 eV, respectively, and the relative content ratio of Pb 0 to the total Pb content (Pb 0 /(Pb 0 +Pb 2+ )) decreased from 6.5% in the control film to 3.8%, indicating the passivating interaction between the ZnPP and the undercoordinated Pb 2+ ions in the perovskite film. As shown in Figure 1g, the binding energy of Zn 2 p 3/2 at 1021.81 eV was observed in the ZnPP‐treated perovskite film, suggesting the presence of porphyrin in the perovskite films.…”