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Hole transport layers (HTLs) play a key role in perovskite solar cells (PSCs), particularly in the inverted PSCs (IPSCs) that demand more in its stability. In this study, samarium‐doped nickel oxide (Sm:NiOx) nanoparticles are synthesized via a chemical precipitation method and deposited as a hole transport layer in the IPSCs. Sm3+ doping can reduce the formation energy of Ni vacancy and naturally increase the density of Ni vacancies, thereby rendering increased hole density. Thenceforth, the electronic conductivity is enhanced significantly, and work function enlarged in the Sm:NiOx film in favor of extracting holes and suppressing charge recombination. Consequently, the Sm:NiOx‐based IPSCs attain outstanding power conversion efficiencies as high as 20.71%. Even when it is applied in flexible solar cells, it still outputs efficiency as high as 17.95%. More importantly, the Sm:NiOx is compatible with large‐scale processing whereby the large area IPSCs of 1.0 cm2 and 40 × 40 mm2 deliver high efficiencies of 18.51% and 15.27%, respectively, all are among the highest for the inorganic HTLs based IPSCs. This research demonstrates that, while revealing the doping effect in depth, Sm:NiOx can be a promising hole transport material for fabricating efficient, large‐area, and flexible IPSCs in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • Acetate ion functionalized polar ionic liquid (IL), 1-allyl-3-methylimidazolium acetate (AMIMOAc), has firstly been used not only as an additive in MAPbI 3 perovskite film but also as an interfacial modification layer between SnO 2 and MAPbI 3 in carbon counter electrode-based perovskite solar cells. • The appropriate content of IL can reduce the number of trap states in MAPbI 3 perovskite film to inhibit non-radiative recombination and increase carrier lifetime, further improve the PCE to 15.16%. • The stability of the devices has been improved remarkably. The device with AMIMOAc IL has retained 93% of its initial PCE after storing for 500 h. The potential of perovskite solar cells as a representative alternative to silicon-based solar cells has become significant owing to their unparalleled advancement in efficiency. However, the intrinsic instability of perovskite still hinders their large-scale commercial application, particularly of the decomposition of perovskite during device operation. To address this issue, an acetate-ion-functionalized polar ionic liquid, 1-allyl-3-methylimidazolium acetate (AMIMOAc), is used as an additive in MAPbI 3 film. FTIR spectroscopy measurements show that AMIMOAc can anchor the organic cations via hydrogen bonding and enhance the Pb–O interaction in modified MAPbI 3 , leading to a continuous and dense morphology to increase the stability of MAPbI 3. After optimizing the concentration of AMIMOAc, an additional interfacial modification layer accelerates the electron extraction and transport. By the synergy of both additive engineering and interface modification, the device not only achieves a high efficiency of 15.16%, but also maintains 93% of the initial PCE after 500 h, showing significantly improved stability. These results pave the way to a new strategy to improve efficiency and long-term stability of carbon counter electrode-based PSCs. [ABSTRACT FROM AUTHOR]

The organic–inorganic perovskite compound (CH 3 NH 3 ) 3 Bi 2 I 9 (MBI) has lower toxicity and higher stability than lead-based perovskite. In this work, we fabricated MBI perovskite-based solar cells (PSCs) through a two-step sequential-solution process by using rutile TiO 2 nanorod array (NRA) films as the electron transporting layer (ETL) for the first time. The thickness, roughness, and crystal structure of the rutile TiO 2 NRAs prepared by hydrothermal method with different reaction times were thoroughly characterized and correlated with the photovoltaic performance of PSCs. Results of morphological and structural analyses, as well as time-resolved photoluminescence studies, indicated the effect of TiO 2 NRA film thickness on the carrier recombination and photovoltaic performance of MBI-based PSCs. The MBI-based device was also stable in an environment with >50% humidity for more than 67 days. [ABSTRACT FROM AUTHOR]

Defects at the surface and grain boundaries of three-dimensional (3D) organic-inorganic metal halide perovskite films lead to the non-radiative recombination of charge carriers and accelerate perovskite decomposition. In turn, this deteriorates the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). Herein, p -methylphenylmethylammonium iodide (p -MePMAI) was reacted with a 3D perovskite to in - situ form a two-dimensional (2D) perovskite upper layer. This upper layer passivated the surface and grain boundary defects of the 3D perovskite film, improving its surface hydrophobicity. As a result, a carbon counter electrode (CE)-based 2D/3D PSC achieved a maximum PCE of up to 15.63%, which was much higher than that of an unmodified 3D MAPbI 3 PSC (12.16%). Moreover, the unencapsulated 2D/3D device maintained 80% of its initial PCE after exposure to air for 700 h with a relative humidity (RH) of 40 ± 5%. This research opens a new pathway for the successful construction of stable and efficient 2D/3D PSCs with organic ammonium salts. [Display omitted] • The p -MePMAI treatment can effectively passivate surface/interface defects and improve the performance of PSCs. • The champion device has a PCE of 15.63% with J sc of 22.15 mA cm−2, V oc of 1.101 V, and FF of 0.64. • The 2D hybrid passivation layer can further increase the stability by preventing contact of water with the 3D perovskite. [ABSTRACT FROM AUTHOR]