A Special Additive Enables All Cations and Anions Passivation for Stable Perovskite Solar Cells with Efficiency over 23%

Mixed-halide perovskite has an irreplaceable role as wide-bandgap absorber in multi-junction tandem solar cells. However, large open-circuit voltage (V oc ) loss due to non-uniform halide distribution and compromised device stability due to photo-induced halide segregation has significantly limited the applications. Here, it is introduced 4-(2-aminoethyl)-benzenesulfonyl fluoride hydrochloride (ABF) with multifunctional groups (sulfonyl, ammonium, and fluoride) to the mixed-halide precursor to demonstrate a downward homogenized crystallization strategy for suppressing the initial vertical halide phase separation during perovskite crystallization and reducing V oc loss. Furthermore, fluoride with strong electronegativity effectively fixes anions and cations, while sulfonyl and ammonium are used to passivate positive charged (halide vacancies) and negative charged (FA/MA vacancies) defects, respectively, thereby reducing the generation of ion vacancies that lead to subsequent photo-induced halide segregation. As a result, the 1.63 and 1.68 eV wide-bandgap perovskite solar cells with inverted structures exhibit the champion power conversion efficiency (PCE) of 21.76% and 20.11% with V oc of 1.18 and 1.21 V, respectively. Most importantly, the optimized devices without encapsulation preserve 86% of initial efficiency after 240 h of continuous illumination under AM 1.5G, showing excellent light stability. Thus, the homogenized crystallization strategy provides highly efficient performance and stability for future tandem solar cell applications.

Section: Resultsmentioning

confidence: 86%

Downward Homogenized Crystallization for Inverted Wide‐Bandgap Mixed‐Halide Perovskite Solar Cells with 21% Efficiency and Suppressed Photo‐Induced Halide Segregation

Zheng

Liang

et al. 2022

“…[19,20] The interactions between ions are effective methods to inhibit ion mitigation and passivation defects. [21,22] In this work, two ionic liquid (IL) additives, namely 1-Butyl-1-methylpyrrolidinium Chloride (BMPyrCl), and 1-Butyl-3-methylpyridinium Chloride (BMPyCl), are introduced into perovskite precursors for the fabrication of Cs 2 AgBiBr 6 thin films. Bromide ion (Br -) is pinned in the perovskite structure through the cation-Brinteraction, resulting in mitigated ion migration and reduced defect states.…”

mentioning

confidence: 99%

Pinning Bromide Ion with Ionic Liquid in Lead‐Free Cs₂AgBiBr₆ Double Perovskite Solar Cells

Meng

et al. 2022

Lead‐free Cs2AgBiBr6 double perovskite has received widespread attention because of its non‐toxicity and high thermal stability. However, intrinsic bromide ion (Br–) migration limits continuous operation of Cs2AgBiBr6‐based perovskite solar cells (PSCs). Herein, an operational and simple strategy is carried out to improve the power conversion efficiency (PCE) and long‐term stability of Cs2AgBiBr6‐based PSCs by introducing 1‐butyl‐1‐methylpyrrolidinium chloride (BMPyrCl) and 1‐butyl‐3‐methylpyridinium chloride (BMPyCl) ionic liquids (ILs). The higher binding energy between Br– in Cs2AgBiBr6 and cation in IL containing pyrrole can inhibit Br– migration effectively, thereby reducing film defects and improving energy level matching. The optimized PCE of 2.22% is obtained for hole transport layer‐free, carbon‐based PSC, which hardly degrades at 40% ± 5% relative humidity and 25 °C for 40 days. This work highlights an effective method to mitigate the halide migration in Cs2AgBiBr6 perovskite, thus providing an effective route in promoting the development of lead‐free double PSCs.

“…The PSC with IDT-OD presents lower reverse current density and higher slope than the control PSC, which declares the suppression of charge accumulation at interface and the improvement of carrier injection and transport. [51,52] In addition, on the basis of the Mott-Schottky curves, the built-in potentials are 1.11 V for the pristine device and 1.15 V for IDT-OD passivated PSC (Figure 4g), respectively. The large built-in potential is considered to promote the separation, transport, and collection of carriers.…”

Section: Resultsmentioning

confidence: 99%

Symmetrical Acceptor–Donor–Acceptor Molecule as a Versatile Defect Passivation Agent toward Efficient FA_0.85MA_0.15PbI₃ Perovskite Solar Cells

Zhao

Lin

et al. 2022

Self Cite

Despite the swift development in perovskite solar cells (PSCs), suppressing the ion defects in the perovskite bulk and further extending the long-lasting stability of the cells remain the concerned issues that are yet to be solved. Here, a symmetrical organic acceptor−donor−acceptor (A−D−A) molecule with the core architecture of indaceno[1,2-b:5,6-b']dithiophene (IDT) and bilateral arms of oxindole, named IDT-OD, as a versatile defect passivation agent, is adopted to inactivate the nonradiative recombination sites in the perovskite absorber. The S element in the IDT unit and carbonyl group CO in the bilateral acceptor unit as the Lewis-base contributes to the passivation sites that are the under-coordinated Pb 2+ cation defects and the N−H group in oxindole unit interacts with halide dangling bonds. The molecular structure with its symmetrical double arms assists the formation of a superior perovskite layer with enlarged grain size, smooth surface topography, hydrophobic property, and low density of defect state. Consequently, the corresponding PSCs with the proper IDT-OD additive yield a remarkable increase in efficiency from 22.77% to 24.04%, along with excellent long-term environmental and thermal stabilities. This study offers a propitious approach for ionic defect passivation engineering toward high-performance PSCs.