All-inorganic perovskite solar cells (PVSCs) have drawn increasing attention because of their outstanding thermal stability. However, their performance is still inferior than the typical organic-inorganic counterparts, especially for the devices with p-in configuration. Herein, we successfully employ a Lewis base small molecule to passivate the inorganic perovskite film, and its derived PVSCs achieved a champion efficiency of 16.1% and a certificated efficiency of 15.6% with improved photostability, representing the most efficient inverted all-inorganic PVSCs to date. Our studies reveal that the nitrile (C-N) groups on the small molecule effectively reduce the trap density of the perovskite film and thus significantly suppresses the non-radiative recombination in the derived PVSC by passivating the Pb-exposed surface, resulting in an improved open-circuit voltage from 1.10 V to 1.16 V after passivation. This work provides an insight in the design of functional interlayers for improving efficiencies and stability of all-inorganic PVSCs.

Polymer hole-transport layers (HTLs) are critical components of inverted perovskite solar cells (IPVSCs). Triphenylamine derivatives PTAA (poly[bis (4-phenyl)(2,4,6-trimethylphenyl)amine]) and Poly-TPD (poly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine]) have been widely adopted as hole-transport materials due to their perovskite passivation effects and suitable energy levels. However, the passivation mechanism (i.e., the functional group responsible for perovskite passivation) of triphenylamine derivative polymers remains unclear, hindering the development and application of this polymer type. Here, we develop a novel Poly-TPD derivative, S-Poly-TPD, by replacing the n-butyl functional group of Poly-TPD with an isobutyl group to explore the influence of alkyl groups on HTL performance and top-deposited perovskite properties. Compared with Poly-TPD, the increased CH 3 -terminal unit density and the decreased spatial distance between the -CH-CH 3 and -CH 2 -CH 3 units and the benzene ring in S-Poly-TPD not only enhanced the hole-transport ability but also improved the perovskite passivation effect, revealing for the first time the role of the alkyl groups in perovskite passivation. As a result, the S-Poly-TPD-based IPVSCs demonstrated high power-conversion efficiencies of 15.1% and 21.3% in

The energy loss (Eloss) control via interfacial engineering is a significant indispensible methodology to realize high‐performance all‐inorganic perovskite solar cells (PVSCs). Herein, three novel polytriphenylamine‐based polymer derivatives (H‐Z1, H‐Z2, and H‐Z3) are synthesized, and the energy levels of these polymers are tuned feasibly through introducing the electron‐withdrawing group of trifluoromethyl in the triphenylamine (TPA) unit. These very deep HOMO energy levels are very beneficial for improving the open‐circuit voltages (Vocs) in PVSCs with the potentially decreased Elosss. Due to the gradual deepening of HOMO energy levels from H‐Z1, H‐Z2 to H‐Z3, the Vocs are elevated from 1.23, 1.28 to 1.30 V, respectively, where the Elosss are decreased from 0.69, 0.64, to 0.62 eV for H‐Z1, H‐Z2, and H‐Z3, respectively. Interestingly, both of the H‐Z1‐ and H‐Z2‐based devices show the highest PCEs, over 14%, in all‐inorganic PVSCs, which are effectively comparable to the results of reference device using Spiro‐OMeTAD as HTL. Thus, through the efficient atomic engineering and chemical modification in corresponding p‐typed polymers, excellent hole transport polymers are achieved for high‐performance and stable PVSCs with very low Eloss.

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