Acetylammonium chloride as an additive for crystallization control and defect passivation in MAPbI₃ based perovskite solar cells

Abstract

Uniform and high-electronic-quality perovskite thin films are necessary for high efficiency perovskite solar cells (PSCs) and additives play a major role in improving the quality of the perovskite films. Here, we demonstrate acetylammonium chloride (AAC) as an additive to effectively control the morphology and crystal quality of the methylammonium lead iodide perovskite film. AAC incorporated PSCs have shown an improved power conversion efficiency (PCE) of 15.9% compared to 14.9% of the control device. Furthermore, AAC incorporated PSCs exhibit high operational stability by retaining 89% of the initial efficiency after 150 hours of continuous operation while the control devices degrade to 51% of the initial PCE in just 45 hours. The improved performance and stability of the AAC incorporated PSCs can be attributed to the (1) formation of uniform sized perovskite films of larger grains and (2) passivation of defects present in the grain boundaries and surfaces of the perovskite film. The defect density has reduced from 4.1x1016 cm-3 to 1.97x1016 cm-3 on addition of AAC to the perovskite film. The reduction in defects-induced non-radiative recombination decay pathways, as further verified from impedance and capacitance-frequency measurements, has caused an enhancement in the open circuit voltage of the AAC incorporated devices and thus an improvement in the PCE and stability of the devices.

Lead-Free Perovskite Homojunction-Based HTM-Free Perovskite Solar Cells: Theoretical and Experimental Viewpoints

“…In addition, the performance of PSCs is significantly influenced by the characteristics of the interface layers. It is widely speculated that low-quality interfaces result in larger surface/interface defect densities, which in turn increase the recombination of charge-carriers [ 74 ]. We assume that the defect densities of IDL1 and IDL2 range between 10 18 and 10 22 cm −3 in order to discuss the impact of the defect density of the interface layers on the PSC performance.…”

Enhancing the Efficiency and Stability of Perovskite Solar Cells through Defect Passivation and Controlled Crystal Growth Using Allantoin

“…Numerous initiatives have been made to address the aforementioned issues, including interfacial, compositional, device structure, crystallization, and additive engineering. − Introduction of additives into the perovskite precursor solution can help in controlling the crystal growth of perovskite films and the passivation of defects. Additives that mix with precursors have been shown to effectively delay the crystallization process and, as a result, enhance homogeneous nucleation and crystallization kinetics. − Zou et al have reported the underlying relationship among crystallization dynamics, charge carrier kinetics, device performance, and device operational stability under ambient conditions with the introduction of ionic liquid additives, which can control the crystal growth.…”

“…The deep level defects that are present in the perovskite bulk and surface act as recombination centers for charge carriers, which results in the reduced open-circuit voltage ( V OC ) of the PSCs. Effective passivation of these defects can be achieved by the addition of Lewis base or acids, ionic liquids, quantum dots, fullerene derivatives, and inorganic salts, which can annihilate defect-induced charge traps. ,,− Prior research has shown that carbonyl groups possessing lone pair electrons act as Lewis bases and demonstrate robust passivation capabilities by forming coordination bonds with under-coordinated lead ions. , Also, it is reported that amino groups can form hydrogen bonds with interstitial iodine. , Additives described in the literature typically have one or two functional groups that aid in defect passivation. Other parts of the additive are inactive and have no interactions with the perovskite layer.…”

Controlling Lead Halide Residue in Perovskite Solar Cells: A Method to Improve the Photostability and Hysteresis

“…[1,2] The progress is due to various improvements in the processing of perovskite films (PFs) and a better understanding of its transport properties, bandgap tuning, absorption coefficient, and crystallization properties. [3][4][5][6][7][8][9][10][11] The high-performance PSCs are usually made with lead (Pb) as its B content in its ABX 3 structure, where A can be methylammonium (MA), formamidinium (FA), cesium (Cs), or mixed cations, and X can be chlorine (Cl), bromine (Br), and iodine (I) or a combination. [12][13][14] The performance and stability of the PSCs majorly depend on the PF quality and its contents.…”

“…[15,16] PFs are prepared by two-step or single-step spin-coating methods. [11,17] Perovskite crystal growth leading to good quality PFs depends on thermodynamic conditions, solvent properties, and environmental conditions such as humidity, temperature, etc. Even though the precursor solutions are prepared in stoichiometric ratios, inadvertently, most of the PFs are formed with excess or less lead iodide (PbI 2 ).…”