The Role of Diammonium Cation on the Structural and Optoelectronic Properties in 3D Cesium–Formamidinium Mixed‐Cation Perovskite Solar Cells

Abstract

Incorporating diammonium cations, which electrostatically connect the adjacent inorganic slabs ([PbI6]4−), into 3D perovskite is recently proposed to develop high‐performance perovskite solar cells (PSCs). However, due to limited studies, the effects of these organic cations on the perovskite structural and optoelectronic properties are yet to be understood. Herein, a diammonium cation, propane‐1,3‐diammonium (PDA), is first proposed to modulate the cesium–formamidinium (Cs–FA)‐mixed cation perovskite. By increasing the PDA content, the efficiency of the Cs0.15FA0.85 − xPDAxPbI3 PSC first increases and then drastically decreases. The highest power conversion efficiency (PCE) of 18.10% obtained by Cs0.15FA0.83PDA0.02PbI3 is superior to that of the Cs0.15FA0.85PbI3 (16.82%). Through systematic investigations, it is revealed that the PDA content–dependent efficiency is attributed to a competition between the enhanced defect passivation and emerged excitonic effect with an increased PDA content. Moreover, the encapsulated Cs0.15FA0.83PDA0.02PbI3 device exhibits almost 1.5 times increased stability than the Cs0.15FA0.85PbI3 counterpart, with 83% of its initial efficiency retained after 500 h exposure, under continuous light soaking at 60 °C in ambient air. This study provides a practical strategy to enhance the device stability without sacrificing the efficiency and deepens our understanding on effects of diammonium cation incorporated in 3D perovskite.

Simultaneous Cesium and Acetate Coalloying Improves Efficiency and Stability of FA0.85MA0.15PbI3 Perovskite Solar Cell with an Efficiency of 21.95%

“…The index of hysteresis is remarkably reduced from 15.0% to 4.8% after alloying 1.2 mol% CsAc (Figure S5, Supporting Information). Thus, the hysteresis phenomenon is effectively inhibited, suggesting the charge transport is quite efficient and more balanced, which may be due to the inhibited ionic migration by the reduced defects density in the alloyed device. To confirm the J sc values extracted from the J – V curves, the external quantum efficiency (EQE) and stabilized power output characterization are conducted.…”

FA‐Assistant Iodide Coordination in Organic–Inorganic Wide‐Bandgap Perovskite with Mixed Halides

“…Hybrid halide perovskites are charming photovoltaic materials for its excellent photovoltaic performance and tuneable bandgap ( E g ) (1.18–2.3 eV) 1–11. Recently, wide‐bandgap and narrow‐bandgap combined two‐junction (perovskite/perovskite and perovskite/silicon) photovoltaic tandem devices are attracting tremendous attention for its potential of high power‐conversion‐efficiency (PCE) (46.1%) 12–21.…”

Interfacial Structure and Composition Managements for High‐Performance Methylammonium‐Free Perovskite Solar Cells

“…Interestingly, the PDA cation was also found to be an effective in-bulk passivation agent. [34] The results of the contact angle tests are shown in Figure 4c. It can be seen that the water droplet contact angles of the reference, PAI-treated and PDAI 2 -treated films are 59.4°, 69.8°, and 79.3° respectively, indicating the increased hydrophobicity of the perovskite films following the alkylammonium halide treatments.…”

“…[2,4] Although the optical bandgap of FAPbI 3 (1.45-1.48 eV in thin films) [5,6] is closer to the theoretically optimal bandgap (1.34 eV for semiconductors) [7,8] than that of MAPbI 3 (1.58 eV) [9] , the undesirable conversion from the perovskite phase (α-FAPbI 3 ) to the photoinactive phase (δ-FAPbI 3 ) at room temperature has restrained the direct application of FAPbI 3 in PSCs. [10,11] The α-to-δ phase transition has been (R stands for an alkyl chain of 2, [31,32] 3, [33,34] 6, [33] and 8 [33] carbons). For the widely used alkylammonium halides, the proper amount of ethylammonium (EA + ) and ethane-1,2-diammonium (EDA 2+ ) cations (alkyl chain of 2 carbons) can be incorporated into the 3D perovskite lattice, while the interaction between the ammonium cations with longer alkyl chains and the 3D perovskite is ambiguous.…”