Chlorides, other Halides, and Pseudo‐Halides as Additives for the Fabrication of Efficient and Stable Perovskite Solar Cells

Abstract

Perovskite solar cells (PSCs) are attracting a tremendous attention from the scientific community due to their excellent power conversion efficiency, low cost, and great promise for the future of solar energy. The best PSCs have already achieved a certified power conversion efficiency (PCE) of 25.5 % after an unprecedented rapid performance rise. However, high requirements with respect to large area, high‐efficiency devices, and stability are still the challenges. Major efforts, especially for achieving a high degree of chemical control, have been made to reach these targets. The use of halide additives has played a critical role in improving the efficiency and stability. The present paper reviews the important breakthroughs in PSC technologies made by using halide additives, especially chloride, and pseudo‐halide additives for the preparation of the perovskite layers, other layers, and interfaces of the devices. These additives help perovskite (PVK) crystallization and layer morphology control, grain boundary reduction, bulk and interface defects passivation, and so on. Normally, these halide additives play different roles depending on their categories and their location. Herein, recent progresses made due to additives employment in every possible layer of PSCs are reviewed, with focus on chloride, other halides, and pseudo‐halides as additives in PVK films, halide additives in carrier transport layers, and at PVK‐contact interfaces. Finally, an outlook of engineering of these additives in PSC progress is given.

Fast Solidification and Slow Growth Strategy for High‐Performance Quasi‐2D Perovskite Solar Cells

“…Moreover, the introduction of the ACN/MA/EtOH solvent system also results in a reduction in full‐width‐at‐half‐maximum (FWHM) value (0.169° vs 0.130°) for the (111) peak in contrast to the anti‐solvent one, which, according to the Scherrer equation, indicates a larger crystallite size. [ 52 ]…”

“…Moreover, the introduction of the ACN/MA/ EtOH solvent system also results in a reduction in full-widthat-half-maximum (FWHM) value (0.169° vs 0.130°) for the (111) peak in contrast to the anti-solvent one, which, according to the Scherrer equation, indicates a larger crystallite size. [52] The preferred orientation and crystalline quality of the antisolvent and the FSSG perovskite films were further investigated by the grazing incidence wide-angle X-ray scattering (GIWAXS) measurements, and the corresponding 2D patterns are displayed in Figure 3 and Figure S6, Supporting Information. The perovskite film fabricated from anti-solvent process exhibits a strong diffraction ring, indicating orientation randomness.…”

Cs4PbI6-Cl Nucleation Seeds Assisted Highly-Oriented Inorganic CsPbI3 Perovskites for Efficient Perovskite Solar Cells

“…20 Therefore, organic chloride additives, such as methylammonium chloride (MACl) and formamidinium chloride (FACl), were applied in the perovskite precursor solutions to form the intermediate species and regulate the crystallization of perovskite films. 21,22 carrier transport by adding amino-functionalized carbon nanotubes and MACl. 23 Limited by the solubility of the MACl in the precursor, Yoon et al obtained highly uniform and pinhole-free CsPbI 3 perovskite films by sequentially dripping MACl solution to control the intermediate stages of the crystallization process.…”

“…The additive engineering of perovskite precursor solutions has become one of the most promising strategies to improve the crystal quality and suppress defects of the CsPbI 3 perovskite films by forming intermediate complexes during the crystallization of the perovskite films. − Yang et al found that the Cl – ions would benefit the nucleation of the perovskites without entering into the perovskite lattice, leading to perovskites with improved optoelectronic properties being obtained . Therefore, organic chloride additives, such as methylammonium chloride (MACl) and formamidinium chloride (FACl), were applied in the perovskite precursor solutions to form the intermediate species and regulate the crystallization of perovskite films. , Wang et al fabricated high crystalline uniaxial-orientated perovskite films with enhanced charge-carrier transport by adding amino-functionalized carbon nanotubes and MACl . Limited by the solubility of the MACl in the precursor, Yoon et al obtained highly uniform and pinhole-free CsPbI 3 perovskite films by sequentially dripping MACl solution to control the intermediate stages of the crystallization process .…”

Effect of Organic Chloride Additives on the Photovoltaic Performance of MA‐Free Cs0.1FA0.9PbI3 Perovskite Solar Cells

“…[30][31][32] Generally, Cl additives are known to tune the film formation for perovskites, leading to improved morphology and high crystallinity, and consequently solar cell performance in most cases. [33] But the analysis of published literature showed that there are few studies dedicated to gaining a deeper insight into the underlying mechanisms behind the properties improvements using organic additives besides the popular MACl additive which should be avoided due to possible incorporation of MA into the host perovskite lattice capable of slightly blueshifting the bandgap in addition to its propensity to easily undergo thermal decomposition. [34] In this work, we investigate and compare EACl, PACl, and BACl additives and then double BACl-EACl additives for Cs 0.1 FA 0.9 PbI 3 films and PSCs.…”