Carbon-based inorganic perovskite solar cells (C-PSCs) have attracted intensive attention owing to their low cost and superior thermal stability. However, the bulk defects in perovskites and interfacial energy level mismatch seriously undermine their performance. To overcome these issues, a multifunctional dualinterface engineering is proposed with a focus on low-temperature CsPbI 2 Br C-PSCs, where the potassium trifluoroacetate (KTFA) and the 4-trifluorophenyl methylammonium bromide (CF 3 PMABr) are introduced beneath and on top of the perovskite layer, respectively. It is found that TFAions locate at the SnO 2 /CsPbI 2 Br interface, whereas a small amount of K + ions diffuse into perovskite lattice to participate in nucleation and crystallization, resulting in more favored interfacial energy level alignment, improved film quality, passivated interfacial defects, released interfacial strain, as well as suppressed charge recombination and ion migration. Meanwhile, the CF 3 PMABr passivates I/Br vacancies and forms 2D perovskite capping layer to facilitate hole extraction at the CsPbI 2 Br/carbon interface. As a result, a remarkable power conversion efficiency (PCE) of 14.05% with an open-circuit voltage of 1.273 V is achieved. To the best of the authors' knowledge, it is currently the highest PCE reported for low-temperature CsPbI 2 Br C-PSCs. Furthermore, the nonencapsulated device exhibits improved moisture, thermal, and illumination stability in ambient air.

Solution‐processed nickel oxide nanocrystals (NiOx NCs) ink can be facilely applied to deposit NiOx thin films as the hole transport layer (HTL) for perovskite solar cells (PSCs). Both the efficiency and stability of the corresponding PSCs depend significantly on the size and the energy levels of the as‐synthesized NiOx NCs; however, previous studies have shown that these two aspects can be hardly controlled synchronously to maximize the device performance. Herein, a novel synthesis of highly dispersed NiOx NCs is demonstrated by employing tetraalkylammonium hydroxides (TAAOHs, alkyl = methyl, ethyl, propyl, butyl) as precipitating bases, where the varied alkyl chain lengths of TAAOHs enable the size control of the NiOx NCs and the subsequent altering of their Ni3+ contents, leading to tunable energy levels of the NiOx thin films. With the longest butyl chain, the smallest crystal size and the optimal energy level alignment at the NiOx/perovskite interface are achieved. After further passivating the detrimental Ni3+ species on the surface of NiOx HTL, a remarkable power conversion efficiency (PCE) approaching 23% is obtained, which is one of the highest PCEs reported for NiOx‐based inverted PSCs. Furthermore, the unencapsulated device exhibits excellent ultraviolet stability, which maintains ≈87% of its PCE after 200 h exposure.

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.

device stability. [3][4][5][6][7] Moreover, noble metal electrodes could increase the production costs. [8] Therefore, carbon-based inorganic PSCs (C-IPSCs) with a simple HTL-free architecture have attracted extensive attention, in view of their low costs, simple fabrication process, and excellent long-term stability. [5,9,10] Mixed-halide CsPbI 2 Br perovskite is an appealing photovoltaic material due to its good trade-off between band gap (E g ) and phase stability. [11,12] However, the PCEs of reported CsPbI 2 Br C-IPSCs are still far from their counterparts based on the organic HTLs and noble metal electrodes owing to bulk defects and interfacial energy level mismatch. [5] To address these issues, composition and additive engineering have been widely used to optimize perovskite quality and passivate film defects. [13][14][15][16] Besides, some functional materials are also employed as the interlayers to adjust the energy level alignment of CsPbI 2 Br/carbon interface. [10,[17][18][19] Unfortunately, the above studies mainly focus on the perovskite or its top interface modification, while ignoring the electron transport layer (ETL)/CsPbI 2 Br buried interface. Actually, the defects at the bottom interface is even higher than that on top, due to the accumulation of deep level defects, which will cause poor electron transport and severe ion migration, resulting in current density-voltage (J-V) hysteresis and device instability issues. [8,11,20,21] Regarding the typical ETLs such as tin oxide (SnO 2 ) and titanium oxide (TiO 2 ) nanoparticles, up to 30% of the atomic bonds are dangling bonds, which will cause a large number of oxygen defects (O defects ) including oxygen vacancies (O v ) and surface hydroxyl (OH) groups defects (O OH )). [11,22,23] Meanwhile, these dangling states are considered fatal, because the imperfect lattice arrangements can damage its electronic properties, resulting in charge recombination and energy level mismatch with perovskite films. [11,21] On the other hand, interfacial strain and lattice distortion are inevitable during the rapid crystallization process of perovskite films, which have a significant effect on the defect formation energy, carrier mobility, energy level structure, and ion migration. [24,25] Simultaneously, the interfacial residual stress at the bottom of perovskite films is also the reason for accelerated material degeneration. [26] On account of The charge recombination resulting from bulk defects and interfacial energy level mismatch hinders the improvement of the power conversion efficiency (PCE) and stability of carbon-based inorganic perovskite solar cells (C-IPSCs).Herein, a series of small molecules including ethylenediaminetetraacetic acid (EDTA) and its derivatives (EDTA-Na and EDTA-K) are studied to functionalize the zinc oxide (ZnO) interlayers at the SnO 2 /CsPbI 2 Br buried interface to boost the photovoltaic performance of low-temperature C-IPSCs. This strategy can simultaneously passivate defects in ZnO and perovskite films, adjust interfacial energy ...

Low band gap tin‐lead perovskite solar cells (Sn−Pb PSCs) are expected to achieve higher efficiencies than Pb‐PSCs and regarded as key components of tandem PSCs. However, the realization of high efficiency is challenged by the instability of Sn2+ and the imperfections at the charge transfer interfaces. Here, we demonstrate an efficient ideal band gap formamidinium (FA)‐based Sn−Pb (FAPb0.5Sn0.5I3) PSC, by manipulating the buried NiOx/perovskite interface with 4‐hydroxyphenethyl ammonium halide (OH‐PEAX, X=Cl−, Br−, or I−) interlayer, which exhibits fascinating functions of reducing the surface defects of the NiOx hole transport layer (HTL), enhancing the perovskite film quality, and improving both the energy level matching and physical contact at the interface. The effects of different halide anions have been elaborated and a 20.53 % efficiency is obtained with OH‐PEABr, which is the highest one for FA‐based Sn−Pb PSCs using NiOx HTLs. Moreover, the device stability is also boosted.