Suppressing Nickel Oxide/Perovskite Interface Redox Reaction and Defects for Highly Performed and Stable Inverted Perovskite Solar Cells.

The inorganic hole transport layer of nickel oxide (NiOx ) has shown highly efficient, low-cost, and scalable in perovskite photovoltaics. However, redox reactions at the interface between NiOx and perovskites limit their commercialization. In this study, ABABr (4-(2-Aminoethyl) benzoic acid bromide) between the NiOx and different perovskite layers to address the issues has been introduced. How the ABABr interacts with NiOx and perovskites is experimentally and theoretically investigated. These results show that the ABABr molecule chemically reacts with the NiOx via electrostatic attraction on one side, whereas on the other side, it forms a strong hydrogen bond via the NH3 + group with perovskites layers, thus directly diminishing the redox reaction between the NiOx and perovskites layers and passivating the layer surfaces. Additionally, the ABABr interface modification leads to significant improvements in perovskite film morphology, crystallization, and band alignment. The perovskites solar cells (PSCs) based on an ABABr interface modification show power conversion efficiency (PCE) improvement by over 13% and maintain over 90% of its PCE after continuous operation at maximum power point for over 500 h. The work not only contributes to the development of novel interlayers for stable PSCs but also to the understanding of how to prevent interface redox reactions.

Efficient Gradient Potential Top Electron Transport Structures Achieved by Combining an Oxide Family for Inverted Perovskite Solar Cells with High Efficiency and Stability.

Although inverted (p-i-n) structure perovskite solar cells (PSCs) have achieved high efficiency by commonly using fullerenes or their derivatives as electron transport layers (ETLs), the device stability and cost of fullerene materials are still of great concern. Herein, we demonstrate inorganic top ETLs simply composed from a family of metal oxides including In2O3 and its derivative of Sn:In2O3 with a gradient potential structure. For inverted PSCs, the typical film formation process of In2O3 will damage or degrade perovskite materials underneath; thus, we report a low temperature synthesis approach for obtaining In2O3 and Sn:In2O3 nanoparticles that can form effective top ETLs without any post-treatment. The one-family oxide-based top ETL features with the enhanced built-in potential, high electron extraction, and low interfacial recombination, offering a power conversion efficiency (PCE) of 20.65% in PSCs constructed from oxide-only carrier (both hole and electron) transport layers (CTLs), which is the highest efficiency in oxide-only CTL-based inverted PSCs to the best of our knowledge. Equally important, the inverted PSCs based on the Sn:In2O3/In2O3 ETL show the excellent operational stability and remain 90% of the initial value of PCE over 2000 h. Consequently, this work contributes to the robust strategy of all oxide-only CTLs in developing rigid and flexible PSCs for practical photovoltaic applications.

Establishing Multifunctional Interface Layer of Perovskite Ligand Modified Lead Sulfide Quantum Dots for Improving the Performance and Stability of Perovskite Solar Cells.

While organic-inorganic halide perovskite solar cells (PSCs) show great potential for realizing low-cost and easily fabricated photovoltaics, the unexpected defects and long-term stability against moisture are the main issues hindering their practical applications. Herein, a strategy is demonstrated to address the main issues by introducing lead sulfide quantum dots (QDs) on the perovskite surface as the multifunctional interface layer on perovskite film through establishing perovskite as the ligand on PbS QDs. Meanwhile, the multifunctions are featured in three aspects including the strong interactions of PbS QDs with perovskites particularly at the grain boundaries favoring good QDs coverage on perovskites for ultimate smooth morphology; an inhibition of iodide ions mobilization by the strong interaction between iodide and the incorporated QDs; and the reduction of the dangling bonds of Pb2+ by the sulfur atoms of PbS QDs. Finally, the device performances are highly improved due to the reduced defects and non-radiative recombination. The results show that both open-circuit voltage and fill factor are significantly improved to the high values of 1.13 V and 80%, respectively in CH3 NH3 PbI3 -based PSCs, offering a high efficiency of 20.64%. The QDs incorporation also enhances PSCs' stability benefitting from the induced hydrophobic surface and suppressed iodide mobilization.

High Phase Stability in CsPbI3 Enabled by Pb-I Octahedra Anchors for Efficient Inorganic Perovskite Photovoltaics.

CsPbI3 inorganic perovskite has exhibited some special properties particularly crystal structure distortion and quantum confinement effect, yet the poor phase stability of CsPbI3 severely hinders its applications. Herein, the nature of the photoactive CsPbI3 phase transition from the perspective of PbI6 octahedra is revealed. A facile method is also developed to stabilize the photoactive phase and to reduce the defect density of CsPbI3 . CsPbI3 is decorated with multifunctional 4-aminobenzoic acid (ABA), and steric neostigmine bromide (NGBr) is subsequently used to further mediate the thin films' surface (NGBr-CsPbI3 (ABA)). The ABA or NG cation adsorbed onto the grain boundaries/surface of CsPbI3 anchors the PbI6 octahedra via increasing the energy barriers of octahedral rotation, which maintains the continuous array of corner-sharing PbI6 octahedra and kinetically stabilizes the photoactive phase CsPbI3 . Moreover, the added ABA and NGBr not only interact with shallow- or deep-level defects in CsPbI3 to significantly reduce defect density, but also lead to improved energy-level alignment at the interfaces between the CsPbI3 and the charge transport layers. Finally, the champion NGBr-CsPbI3 (ABA)-based inorganic perovskite solar cell delivers 18.27% efficiency with excellent stability. Overall, this work demonstrates a promising concept to achieve highly phase-stabilized inorganic perovskite with suppressed defect density for promoting its optoelectronic applications.