Improving the Performance of Perovskite Solar Cells via a Novel Additive of N,1‐Fluoroformamidinium Iodide with Electron‐Withdrawing Fluorine Group

Abstract

Additives are widely adopted for efficient perovskite solar cells (PSCs), and proper additive design contributes a lot to PSCs' various breakthroughs. Herein, a novel additive of N,1-fluoroformamidinium iodide (F-FAI), whose cation replaces one amino group in guanidinium (GA + ) with electron-withdrawing fluorine group, is synthesized and applied as the additive for PSCs. The electron-withdrawing effect of fluorine promotes the molecular polarity of N,1-fluoroformamidine (F-FA), enhancing the interaction of N,1-fluoroformamidinium (F-FA + ) with MAPbI 3 . Compared with the nonpolar GA + , F-FA + improves the crystallinity, passivates the defect, and downshifts the Fermi level of MAPbI 3 more significantly. The charge transfer and built-in field in printable triple mesoscopic PSCs are therefore enhanced. Moreover, charge transport in MAPbI 3 is also promoted by F-FAI. With these benefits, a power conversion efficiency of 17.01% for printable triple mesoscopic PSCs with improved open-circuit voltage and fill factor is obtained with the addition of F-FAI, superior to the efficiency of 15.24% for those devices with guanidinium iodide additives.

Mechanism of the Dimethylammonium Cation in Hybrid Perovskites for Enhanced Performance and Stability of Printable Perovskite Solar Cells

“…The samples exhibit the absorption thresholds at about 800 nm and change negligibly with x . However, DMA has a larger ionic radius than FA, the incorporation of DMA barely changes the light absorption onset of control perovskite, indicating they don't, or only a few grow into the crystal lattice [ 21 ] but exist in the film in the form of DMAPbI 3 phase, which is consistent with XRD results. Furthermore, there is an obvious enhancement in absorbance for the Cs 0.12 FA 0.85 DMA 0.03 PbI 3 film, indicating the improved crystallization is acquired.…”

Minimizing the Voltage Loss in Hole‐Conductor‐Free Printable Mesoscopic Perovskite Solar Cells

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Nevertheless, the efficiency of the printable mesoscopic PSCs still lags behind the conventional PSCs. Though extensive methods have been conducted to improve the performance of such devices, including additives, [12][13][14][15][16] composition engineering, [17,18] and crystallization control, [18][19][20] the highest PCE reported so far is 18.2% using an acetamidinium mixed methylammonium lead iodide perovskite. [21] In the meantime, though FAPbI 3 perovskites are believed and reported to yield higher PCEs, we only achieved a PCE of ≈16% using FAPbI 3 perovskite.

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Cellulose‐Based Oxygen‐Rich Activated Carbon for Printable Mesoscopic Perovskite Solar Cells

“…At the high frequency region, the semicircle is attributed to the charge transfer resistance (R ct ). [42] The devices with CAC exhibit smaller radius at that region, corresponding to the lower R ct (Figure 5a). The reduced R ct is surmised to be related to the increased WF of the CAC-E and the better interfacial contact between perovskite and CAC-E, which promotes the charge transfer at the interface.…”

“…Device Fabrication: The fabrication process of p-MPSC based on hybrid CEs was according to the reported method. [42] The FTO conducting glass was etched with a laser to form desired electrode patterns before being ultrasonically cleaned with detergent solution, deionized water and ethanol for 15 min, respectively. Then, a compact TiO 2 layer was deposited on the substrate by a spray pyrolysis deposition method at 723 K with an isopropanol solution containing diisopropoxytitanium bis(acetylacetonate) and sintered at 723 K for 10 min.…”