Methylammonium Iodide-Mediated Controlled Crystal Growth of CsPbI₂Br Films for Efficient and Stable All-Inorganic Perovskite Solar Cells

Abstract

A high-quality perovskite film is a key aspect contributing to high photovoltaic performance of all-inorganic perovskite solar cells. We herein demonstrate that the addition of methylammonium iodide (MAI) influences effectively both the tailored film morphology and precise crystal growth to construct high-quality CsPbI2Br films. It is found that an MAI additive retards the crystallization kinetics to control the inorganic perovskite films to form a highly crystalline α-CsPbI2Br structure consisting of microsized grains with reduced defect density. The optimal MAI additive (10 wt %) achieves a power conversion efficiency (PCE) of 10.40% for the CsPbI2Br-based all-inorganic perovskite solar cells, which is >30% enhancement from 6.95% of the pristine one. The solar cells employing the MAI additive possess high operational and thermal stability, retaining >70% of the original PCE after aging for 1500 h in ambient atmosphere and under continuous heating at 85 °C for 30 h, respectively. The photovoltaic performance with an indoor light source was also examined using a white light-emitting diode (6500 K, 1000 lux), showing promising PCEs of 23.51% with a stabilized power output of 21.15%.

On the role of carboxylated polythiophene in defect passivation of CsPbI 2 Br surface for efficient and stable all‐inorganic perovskite solar cells

“…(Figure S1) The crystallinities of CsPbI 2 Br films were investigated by XRD patterns, as shown in Figure 1C. The diffractograms of the perovskite films exhibited α‐phase CsPbI 2 Br perovskite structure with (100) and (200) crystal planes at the diffraction peaks of 14.6° and 29.5°, respectively, which is consistent to the previous reports on α‐phase CsPbI 2 Br perovskite films 5 . No additional peaks or peak shifts were observed in the P3CT passivated films, and the full width half maximum (FWHM) of (100) and (200) peaks were almost unchanged upon P3CT passivation.…”

“…The diffractograms of the perovskite films exhibited α-phase CsPbI 2 Br perovskite structure with (100) and ( 200) crystal planes at the diffraction peaks of 14.6 and 29.5 , respectively, which is consistent to the previous reports on α-phase CsPbI 2 Br perovskite films. 5 No additional peaks or peak shifts were observed in the P3CT passivated films, and the full width half maximum (FWHM) of ( 100) and (200) peaks were almost unchanged upon P3CT passivation. (Figure S2) These results further confirmed that P3CT deposition on CsPbI 2 Br films did not impact the optophysical properties of the perovskite films.…”

“…Recently, CsPbI 2 Br has emerged as a practical inorganic halide perovskite absorber with a mid‐range band‐gap (1.9 eV) and decent phase stability at room temperature 4 . However, the efficiencies of CsPbI 2 Br solar cells achieved to date are still inferior to those of organometal halide perovskites mainly due to imperfect film quality and morphology of CsPbI 2 Br, which induces limited open‐circuit voltage ( V OC ), short‐circuit current density ( J SC ), and fill factor (FF) 5 . Therefore, it is desirable to optimize film properties of CsPbI 2 Br for dense and uniform films with low defect densities.…”

A Key 2D Intermediate Phase for Stable High‐Efficiency CsPbI2Br Perovskite Solar Cells

“…According to the literature, the slower crystallization rate is conducive to improving the quality of perovskite films. [25,27] It should be noted that there are obvious differences in the color of the films with IMX additive at different annealing temperatures, signifying that phase transitions occur during the crystallization process. Eventually, high-quality films with coal-black appearance were obtained in the LDIAG 0.5-IMX and LDIAG 1-IMX systems.…”

Improved phase stability of CsPbI2Br perovskite by released microstrain toward highly efficient and stable solar cells

“…As a result, a pinhole‐free CsPbI 3 film was obtained with improved film stability 11 . While despite the reported progresses on phase stability, these treatments would confine the perovskite crystal growth and significantly decrease the grain sizes, which afford massive charge recombination sites and still limit the device performances 11–15 . Therefore, a more rational design is imperative to evade the lattice distortion under humidity while maintaining large perovskite grain sizes at the meantime 16,17 …”