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The realization of highly efficient perovskite solar cells (PSCs) in ambient air is considered to be advantageous for low‐cost commercial manufacturing. However, it is fundamentally difficult to achieve comparable device performance to that obtained in an inert atmosphere, especially when the ambient humidity is high. Here, an effective precursor engineering that simultaneously employs non‐halide lead acetate and lead thiocyanate lead sources for fabricating high‐quality methylammonium lead iodide perovskite films in ambient air with enhanced moisture tolerance, is reported. The presence of Ac– and SCN– ions not only enables the facile formation of homogeneous and highly crystalized perovskite films, but also directs the uniform growth of the crystals along the (110) direction. Accordingly, a 20.55% efficiency is demonstrated, one of the best results for air‐processed MAPbI3 PSCs, which is also the highest value achieved with non‐halide lead sources. Furthermore, the unencapsulated device shows fivefold prolonged air stability (3600 h) compared to the conventional PbI2‐based PSC. Together with the use of non‐toxic antisolvent, this strategy is fully compatible with ambient air operation and thus of great potential for practical applications. [ABSTRACT FROM AUTHOR]

Quasi‐2D CsPbI3 perovskites have emerged as excellent candidates for advanced photovoltaic technologies due to their fundamentally enhanced stability than conventional 3D counterparts. However, the applications of quasi‐2D perovskites are plagued with their poor out‐of‐plane carrier mobility induced by the intercalated insulating organic layers. In this work, a new strategy is explored to significantly enhance the out‐of‐plane charge transport in quasi‐2D Dion–Jacobson (DJ) CsPbI3 perovskites via leveraging the intercalation of aromatic diamine cations (p‐phenylenediamine, PPDA) with unique π‐conjugated bond based on the first‐principles calculations. The strong interactions between PPDA2+ cations and inorganic Pb‐I framework (i.e., I–I interaction, p‐π coupling, and H‐bonds) provide three carrier pathways to facilitate the out‐of‐plane charge transport. Furthermore, the restricted in‐plane and out‐of‐plane structural distortion induced by the π‐conjugated bond could improve the electronic coupling and charge mobility along the out‐of‐plane direction with reduced bandgaps. As a proof of concept, the calculated average photovoltaic conversion efficiency of such engineered DJ CsPbI3 perovskite solar cells is ≈17%, which is very close to the certificated champion efficiency of 3D α‐CsPbI3, underscoring their potential for solar cell applications. [ABSTRACT FROM AUTHOR]

In perovskite solar cells (PSCs), a defective perovskite (PVK) surface and cliff‐like energy offset at the interface always slow down the charge extraction; meanwhile, interface ion diffusion causes oxidation of the metal electrode, inducing device instability. Here, the in situ grown 2D‐(CH3NH2)3Sb2I9 (MA3Sb2I9) on the back surface of MAPbI3 results in a more robust interface. MA3Sb2I9 changes the MAPbI3 surface to p‐type and thus acts like a back surface field to drive charge extraction and suppress recombination, resulting in an obviously higher fill factor (FF) = 0.8 and power conversion efficiency (PCE) = 20.4% of SnO2/MAPbI3/MA3Sb2I9/Spiro‐OMeTAD (2,2′,7,7′‐Tetrakis[N,N‐di(4‐methoxyphenyl)amino]‐9,9′‐spirobifluorene) PSC than the pure MAPbI3 device. More importantly, strong chemical bonding of SbI prohibits ion diffusion, largely enhancing the thermal stability and longtime stability. Here, special 2D‐MA3Sb2I9 constructs' robust band alignment and chemical environment at the interface are highlighted for efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

Abstract: The phase instability and large energy loss are two obstacles to achieve stable and efficient inorganic‐CsPbI3−xBrx perovskite solar cells. In this work, stable cubic perovskite (α)‐phase CsPbI2Br is successfully achieved by Pb(Ac)2 functioning at the grain boundary under low temperature. Ac− strongly coordinates with CsPbI2Br to stabilize the α‐phase and also make the grain size smaller and film uniform by fast nucleation. PbO is formed in situ at the grain boundary by decomposing Pb(Ac)2 at high‐temperature annealing. The semiconducting PbO effectively passivates the surface states, reduces the interface recombination, and promotes the charge transport in CsPbI2Br perovskite solar cells. A 12% efficiency and good stability are obtained for in situ PbO‐passivated CsPbI2Br solar cells, while Pb(Ac)2‐passivated device exhibits 8.7% performance and the highest stability, much better than the control device with 8.5% performance and inferior stability. This article highlights the extrinsic ionic grain boundary functionalization to achieve stable and efficient inorganic CsPbI3−xBrx materials and the devices. [ABSTRACT FROM AUTHOR]

Abstract: Ionic movement is considered awful in perovskite solar cells (PSCs) for relating with the hysteresis and long‐term instability. However, the positive role of ions to enhance the energy band bending for high performance PSC is always overlooked, let alone reducing the hysteresis. In this work, LiI is doped in CH3NH3PbI3. It is observed that the aggregation of Li+/I− tunes the energy level of the perovskite and induces n/p doping in CH3NH3PbI3, which makes charge extraction quite efficient from perovskite to both NiO and [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) layer. Therefore, in NiO/LiI doped perovskite/PCBM solar cells, Li+ and I− modulate the interface energy band alignment to facilitate the electron/hole transport and reduce the interface energy loss. On the other hand, n/p doping enlarges Fermi energy level splitting of the PSCs to improve the photovoltage. The performance of LiI doped PSCs is much higher with reduced hysteresis compared to the undoped solar cells. This work highlights the positive effect of selective ionic doping, which is promisingly important to design the stable and efficient PSCs. [ABSTRACT FROM AUTHOR]

Perovskite solar cells as a hot research topic show the necessity of controlling the interface. In this work, an insulating alkyl chain layer is self-assembled at the perovskite/hole transport material interface, which successfully exhibits a dual function: blocking electron recombination and resisting moisture at the same time. Improved solar energy conversion efficiency and stability of the device are both achieved. [ABSTRACT FROM AUTHOR]

Fabrication of efficient Pb reduced inorganic CsPbI2Br perovskite solar cells (PSC) are an important part of environment‐friendly perovskite technology. In this work, 10% Pb reduction in CsPb0.9Zn0.1I2Br promotes the efficiency of PSCs to 13.6% (AM1.5, 1sun), much higher than the 11.8% of the pure CsPbI2Br solar cell. Zn2+ has stronger interaction with the anions to manipulate crystal growth, resulting in size‐enlarged crystallite with enhanced growth orientation. Moreover, the grain boundaries (GBs) are passivated by the Cs‐Zn‐I/Br compound. The high quality CsPb0.9Zn0.1I2Br greatly diminishes the GB trap states and facilitates the charge transport. Furthermore, the Zn4s‐I5p states slightly reduce the energy bandgap, accounting for the wider solar spectrum absorption. Both the crystalline morphology and energy state change benefit the device performance. This work highlights a nontoxic and stable Pb reduction method to achieve efficient inorganic PSCs. [ABSTRACT FROM AUTHOR]

We demonstrate the controllable conduction band-edge reconfiguration in quasi-2D Dion-Jacobson α-CsPbI 3 perovskites enabled by dimensional engineering based on the rationally designed organic dipole moments and inorganic layer numbers, which endows the perovskites with fundamentally enhanced electron-hole separation toward efficient photovoltaic applications. [Display omitted] • The discovery of CB-edge reconfiguration in quasi-2D CsPbI 3 perovskites. • The achievement on controllable CB-edge reconfiguration. • The encouraged separation and in-plane transport of charge carriers. Generally, the band-edge configurations of ABX 3 perovskite (where A is MA+/FA+/Cs+ cation, B represents Pb2+ or Sn2+, and X is halogen, respectively) are constructed by the electronic states of B and X ions, implying that A-site cation has no significant contribution to the band edge. In current work, through first-principles calculation, we report the controllable conduction band (CB) edge reconfiguration of quasi-2D Dion-Jacobson α -CsPbI 3 perovskites enabled by dimensional engineering for making A-site cations affect perovskite CB edge, which is based on rationally designed organic chain length (m) of A-site organic spacer cations and inorganic layer numbers (n). It is discovered that the energy level of organic CB would be moved up with the increase of m , and that of inorganic CB would be shifted down with the raise of n , allowing the dimensional engineering of quasi-2D perovskites with controllable CB-edge configuration. Consequently, the achieved CB-edge reconfiguration could endow the quasi-2D perovskites with encouraged carrier separation and in-plane transfer. The discovery of CB-edge reconfiguration in quasi-2D perovskites by dimensional engineering, which is highly meaningful to direct the exploration of advanced perovskites for efficient solar cells. [ABSTRACT FROM AUTHOR]

• Formation of (TMA) x FA 1-x Pb(PF 6) x I 3-x /FAPbI 3 heterojunction through interface ion exchange. • Strong hydrogen bonding and ion size effect stabilize the phase structure. • A champion efficiency of 21.43% was obtained with greatly enhanced device stability. Though formamidinium lead triiodide FAPbI 3 is hotly researched, it still suffers from chemical and phase instabilities, arising from inherent weak chemical bonding and easily transformed crystal configures respectively. This induces depraved opto-electronic properties and device instability, which is imperative to be solved. Here, chemical interaction enhancement in heterostructure of (TMA) x FA 1-x Pb(PF 6) x I 3-x /FAPbI 3 simultaneously improves the chemical and phase stability with preserving its inherent bandgap. Strong hydrogen bonding between PF 6 - and FA+ drastically reduces the α phase formation energy and diminishes the interface trap states. The resulting perovskite solar cells achieve improved efficiency of 21.43% compared with 19.32% of the control device. Meanwhile, ∼90% and 80% of the initial efficiency are maintained for unpacked devices after 1200 h storage (25 °C, 30% relative humidity) and 300 h maximum power point tracking (1 sun, 25 °C, N 2), outperforming the control one. This work highlights a robust interface construction method to overcome the inherent problem of FAPbI 3. [ABSTRACT FROM AUTHOR]