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Comprehensive Summary: Formamidinium (FA)‐based Sn‐Pb perovskite solar cells (FAPb0.5Sn0.5I3 PSCs) with ideal bandgap and impressive thermal stability have caught enormous attention recently. However, it still suffers from the challenge of realizing high efficiency due to the surface imperfections of the transport materials and the energy‐level mismatch between functional contacts. Herein, it is demonstrated that the modification on buried interface with alkali metal salts is a viable strategy to alleviate these issues. We systematically investigate the role of three alkali metal bromide salts (NaBr, KBr, CsBr) by burying them between the NiOx hole transport layer (HTL) and the perovskite light‐absorbing layer, which can effectively passivate interface defects, improve energy‐level matching and release the internal residual strain in perovskite layers. The device with CsBr buffer layer exhibits the best power conversion efficiency (PCE) approaching 20%, which is one of the highest efficiencies for FA‐based Sn‐Pb PSCs employing NiOx HTLs. Impressively, the long‐term storage stability of the unencapsulated device is also greatly boosted. Our work provides an efficient strategy to prepare desired FA‐based ideal‐bandgap Sn‐Pb PSCs which could be applied in tandem solar cells. [ABSTRACT FROM AUTHOR]

We report a solution-processing method to prepare an inorganic LaNiO3 (LNO) hole-transport layer (HTL) under low temperature (<150 °C) for the first time. The inverted PSCs prepared with LNO exhibit high UV-stability and promising efficiency (17.15%). Our preliminary results show great potential for LNO HTL in the fabrication of efficient and photostable inverted perovskite solar cells (PSCs). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Carbon-based CsPbI2Br perovskite solar cells (PSCs) have attracted widespread attention due to their low cost and superior thermal stability. Unfortunately, the bulk defects and interfacial energy level mismatch limit the improvement of device performance. To solve the above issues, we introduce aromatic phenylethylammonium halides (PEAI and PEABr) and their fluorinated derivatives of 4-fluorophenylethylammonium halides (P-F-PEAI and P-F-PEABr) as a passivation layer to post-treat low-temperature CsPbI2Br films. Benefiting from reduced perovskite defects and better energy level alignments, the charge non-radiative recombination is effectively suppressed, and the hole extraction is promoted. Compared with the reference PSCs, the optimized devices achieve a maximum power conversion efficiency (PCE) of 13.97%. To the best of our knowledge, it should be one of the highest PCEs reported among those of low-temperature carbon-based CsPbI2Br PSCs. In addition, nonencapsulated devices exhibit improved moisture and thermal stability in ambient air. [ABSTRACT FROM AUTHOR]

With the advantages of narrow bandgap and excellent thermal stability, fomamidinium lead triiodide (FAPbI3) perovskite holds the promise to boost the power conversion efficiency (PCE) of perovskite solar cells (PSCs) to over 25%. However, such a promise is blurred by the poor structural stability of the black α‐phase FAPbI3, as it can spontaneously transform into photoinactive δ‐phase at room temperature and this process can be accelerated by the ambient moisture. The incorporation of small ions such as cesium (Cs+), methylammonium (MA), and bromide (Br−) into the perovskite lattice is proven to be successful in stabilizing the α‐phase FAPbI3; however, the resultant mixed perovskites suffer the phase segregation problem, which inevitably undermines the long‐term stability of the corresponding PSCs. Therefore, continuous efforts are made to realize stable and pure‐phase α‐FAPbI3 perovskites. Herein, the recent progress on the development of efficient and stable FAPbI3 PSCs is summarized with a focus on the different phase stabilization strategies. In addition, the challenges and possible directions for future study are proposed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Ferroelectric photovoltaic (FE-PV) materials with excellent photocurrent output have stimulated many recent studies in solar energy material fields. How to improve the photocurrent by designing the structure of materials and devices through a simple approach is still a challenge. Here, enhanced photocurrent in Bi2FeMo0.7Ni0.3O6 (BFMNO) ferroelectric thin films is achieved by tuning the thickness of the thin films. With the increase of the thickness, the short circuit current increases first and then decreases. The maximum short circuit current reaches 0.09 mA cm−2 under 100 mW cm−2 when the thickness is 700 nm, which is nearly triple that of the thin film with the thickness of 570 nm. It is proposed that the compensation effect of the driving force comprising the depolarization field and build-in field is the main reason for the enhanced photocurrent. This work highlights a simple approach to enhance the photocurrent of FE-PV materials based on tuning of the thickness. [ABSTRACT FROM AUTHOR]

Double perovskite ferroelectric Bi 2 FeMo x Ni 1- x O 6 (BFMNO) thin films were fabricated using the sol-gel method. The thin films have a broad-band absorption in visible light range of 400–650 nm. With the increase of Mo content, the optical bandgap decreases from 2.19 eV to 2.07 eV. More importantly, the as-prepared BFMNO thin films have self-polarization behavior that causes the forming of the depolarization field and build-in field in the thin films. The narrow band gap and strong ferroelectric self-polarization play a crucial part in improving the photovoltaic effect. The thin film of x  = 0.7 has the optimum open circuit voltage and short circuit current which are 5.41 V and 71.07 μA/cm 2 under light illumination of 110 mW/cm 2 . In addition, the photovoltaic effect of the thin film also exhibits a good adaptability in high temperature environment. This work highlights the applications of the BFMNO thin films as a novel high-performance ferroelectric photovoltaic material. [ABSTRACT FROM AUTHOR]

Gravitational Search Algorithm (GSA) is a widely used metaheuristic algorithm. Although fewer parameters in GSA were adjusted, GSA has a slow convergence rate. In this paper, we change the constant acceleration coefficients to be the exponential function on the basis of combination of GSA and PSO (PSO-GSA) and propose an improved PSO-GSA algorithm (written as I-PSO-GSA) for solving two kinds of classifications: surface water quality and the moving direction of robots. I-PSO-GSA is employed to optimize weights and biases of backpropagation (BP) neural network. The experimental results show that, being compared with combination of PSO and GSA (PSO-GSA), single PSO, and single GSA for optimizing the parameters of BP neural network, I-PSO-GSA outperforms PSO-GSA, PSO, and GSA and has better classification accuracy for these two actual problems. [ABSTRACT FROM AUTHOR]

Ferroelectric polarization is a crucial factor to induce photovoltaic (PV) effect in ferroelectric materials. Here, a novel in‐plane self‐polarization is found for the first time in a polycrystalline Bi2FeMo0.7Ni0.3O6 thin film prepared by the sol–gel process. Different from out‐of‐plane polarization with uniform orientation in the vertical direction, the in‐plane self‐polarization exhibits radialized orientation which points from the center of the thin film to its edges in the horizontal direction. It is demonstrated that the forming of the self‐polarization is attributed to the internal electric field caused by NiBi dipoles. The peculiar polarization induces the region‐dependent ferroelectric PV effect and rectification behavior in the horizontal direction of the thin film. Moreover, in a long time and wide temperature range, the thin film maintains the stable PV properties due to the constant self‐polarization state. This work makes a new cognition for the nature of ferroelectric polarization, and it highlights the Bi2FeMo0.7Ni0.3O6 thin film as a PV and electronic material for peculiar photoelectric devices. A novel in‐plane self‐polarization with radialized polarization orientation is found in ferroelectric Bi2FeMo0.7Ni0.3O6 thin film with narrow bandgap. The peculiar polarization induces a region‐dependent ferroelectric photovoltaic (PV) effect and rectification behavior. The in‐plane self‐polarization state leads to an outstanding stability of the PV properties in long time and at variable temperature. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Formamidinium (FA)‐based Sn‐Pb perovskite solar cells (FAPb0.5Sn0.5I3 PSCs) with ideal bandgap and impressive thermal stability have caught enormous attention recently. However, it still suffers from the challenge of realizing high efficiency due to the surface imperfections of the transport materials and the energy‐level mismatch between functional contacts. Herein, it is demonstrated that the modification on buried interface with alkali metal salts is a viable strategy to alleviate these issues. We systematically investigate the role of three alkali metal bromide salts (NaBr, KBr, CsBr) by burying them between the NiOx hole transport layer (HTL) and the perovskite light‐absorbing layer, which can effectively passivate interface defects, improve energy‐level matching and release the internal residual strain in perovskite layers. The device with CsBr buffer layer exhibits the best power conversion efficiency (PCE) approaching 20%, which is one of the highest efficiencies for FA‐based Sn‐Pb PSCs employing NiOx HTLs. Impressively, the long‐term storage stability of the unencapsulated device is also greatly boosted. Our work provides an efficient strategy to prepare desired FA‐based ideal‐bandgap Sn‐Pb PSCs which could be applied in tandem solar cells. [ABSTRACT FROM AUTHOR]

We report a solution-processing method to prepare an inorganic LaNiO 3 (LNO) hole-transport layer (HTL) under low temperature (<150 °C) for the first time. The inverted PSCs prepared with LNO exhibit high UV-stability and promising efficiency (17.15%). Our preliminary results show great potential for LNO HTL in the fabrication of efficient and photostable inverted perovskite solar cells (PSCs).

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 Sn 2+ and the imperfections at the charge transfer interfaces. Here, we demonstrate an efficient ideal band gap formamidinium (FA)-based Sn-Pb (FAPb 0.5 Sn 0.5 I 3 ) PSC, by manipulating the buried NiO x /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 NiO x 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 NiO x HTLs. Moreover, the device stability is also boosted., (© 2023 Wiley-VCH GmbH.)