High Efficiency Inorganic Perovskite Solar Cells Based On Low Trap Density and High Carrier Mobility CsPbI₃ Films

Abstract

Inorganic perovskite CsPbI3 has exhibited promising performance in single‐junction solar cells, but the grain boundaries (GBs) in its film cause the formation of the defects with deep energy levels (such as iodide vacancy (VI)) and impede the transport of carriers, worsening the efficiency and stability of the solar cells. Here, a CsPbI3 precursor is devised with thiophenol series ligands (TP‐ligands) containing both SH and π‐conjugated molecules. The strong interaction between the SH group (Lewis base) and PbI2 (Lewis acid) suppresses the formation of PbI42− in perovskite solution, thus suppressing the formation of VI in the film accordingly. The terminal groups, such as ‐F and ‐NH2, are employed to achieve an appropriate evaporation speed of the ligands and prevent the oxidation of the thiophenol group, then a high‐quality perovskite film with low trap density is obtained. In addition, the functional group π‐conjugated molecules provide additional carrier transmission channels at the GBs to increase carrier mobility, which facilitates the exciton separation and prolongs the charge lifetime. The CsPbI3 solar cell shows a considerable power conversion efficiency of 20.1% with an open‐current voltage of 1.18 V and a high fill factor of 83.5% and excellent working stability.

Configuration Engineering of Unsymmetrical Structural Hole Transport Material for Efficient and Stable Regular/Inverted Perovskite Solar Cells

“…In addition, as shown in Figure e, “CN” in the imidazole moiety of 2TPA-PI and p -CZDPA-PI were deemed to concentrate more negative charges, therefore, “CN” is supposed to passivate the uncoordinated Pb 2+ on the perovskite surface as a Lewis base. – To prove this interfacial interaction between HTMs and the perovskite, Fourier transform infrared (FTIR) spectroscopy was conducted, as shown in Figure b. The “CN” bond stretching vibrations of pure 2TPA-PI and P-CZDPA-PI powders both appear at 1605 cm –1 whereas after being mixed with PbI 2 , the corresponding stretching vibrations shift to 1601 cm –1 for 2TPA-PI and 1602 cm –1 for p -CZDPA-PI.…”

Illumination Enhanced Crystallization and Defect Passivation for High Performance CsPbI3 Perovskite Solar Cells by Sacrificing Dye

“…[1][2][3][4][5][6] After 2020, the PCE broke 20% successfully, which makes the research of all-inorganic CsPbI 3 PSCs an active research field. [7][8][9][10][11][12][13][14][15][16][17][18][19][20] Recently, the PCEs of CsPbI 3 further stepped up to the plateau of 21%. [21][22][23] In addition, CsPbI 3 perovskite has a suitable bandgap (1.7 eV) to combine with silicon solar cells for tandem device with a theoretical efficiency of 44%.…”

Ligand Engineering of CsPbI3 Quantum Dots for Efficient Solar Cells

“…This process involves the use of anti-solvents, which facilitates the removal of halide ions from the PQD surface, resulting in the formation of halide vacancies and PQD agglomeration . Undercoordinated Pb atoms on the PQD surface, arising from the halide vacancies, act as charge-trapping centers, which impede charge extraction in photovoltaic devices. , Due to the dynamic binding between PQD surfaces and ligands, short-chain ligands are usually dissolved in the anti-solvent to facilitate ligand exchange, leading to surface passivation and improved conductivity. − Recent studies have demonstrated the effectiveness of softer X-type Lewis bases, such as organic carboxylates, amidogen, , and sulfhydryl, in combination with undercoordinated Pb atoms on the PQD surface. Among them, phenethylammonium (PEA) and its derivatives are found to have a positive effect on perovskite passivation, leading to high efficiency and stability in both organic–inorganic perovskite films and PQD films. − However, the poor solubility of PEA in methyl acetate (MeOAc) limits the effectiveness of ligand exchange, resulting in unsatisfactory surface chemistry of PQDs.…”

“…21,22 Due to the dynamic binding between PQD surfaces and ligands, short-chain ligands are usually dissolved in the anti-solvent to facilitate ligand exchange, leading to surface passivation and improved conductivity. 23−26 Recent studies have demonstrated the effectiveness of softer X-type Lewis bases, 27 such as organic carboxylates, 28 amidogen, 29,30 and sulfhydryl, 31 in combination with undercoordinated Pb atoms on the PQD surface. Among them, phenethylammonium (PEA) and its derivatives are found to have a positive effect on perovskite passivation, leading to high efficiency and stability in both organic−inorganic perovskite films and PQD films.…”