Elimination of Interfacial Lattice Mismatch and Detrimental Reaction by Self‐Assembled Layer Dual‐Passivation for Efficient and Stable Inverted Perovskite Solar Cells

Abstract

and modifying the charge transporting layers (CTLs), yet the interfacial mismatch between perovskite and CTLs is a non-negligible issue that dominates the efficiency and stability of corresponding devices. [7][8][9][10][11] Nickel oxide (NiO x ) nanocrystals as a promising stable hole transporting layer (HTL) in inverted p-i-n PVSCs are less prone to hysteresis and work well with flexible or tandem architectures. [12] Nevertheless, the PCE of NiO x -based inverted devices are usual inferior to the organic regular counterparts owing to the several interfacial issues: i) abundant surface traps and mismatch energy level restrict the charge carrier extraction, causing large energy offset; [13] ii) the redox reaction between Ni 3+ and A-site cation salts form a PbI 2 -rich hole extraction barrier, leading to severe interfacial destruction; [14] iii) inconsistent thermal expansion of lattice units in NiO x and perovskite results in tensile strain, prejudicing the microstructure and accelerating the degradation of perovskite. [15][16][17] Therefore, it is urge to solve these issues for performance enhancement and commercialization application of NiO x -based PVSCs.Recently, a great deal of molecular interlayers have been applied to passivate or adjust the energy level of NiO x /perovskite interface for strengthen the efficiency and stability in p-i-n devices, such as inorganic salts, [18][19][20] acids, [21] fullerene derivatives [22] and polymers buffer layer. [23][24][25] Nevertheless, most of the buffer layers are nonconductive and accompanied with the uncontrollable thickness and uniformity, which undoubtedly affect the optimization of charge transfer and perovskite crystal growth. Relatively speaking, the self-assembled small-molecule (SASM) can form thermodynamically favored ordered self-assembled layer that has been extensively proved as effective modifier to modulate the energy level and surface chemical state, as well as enhance the affinities of the deposition layer and substrate. [26] For instance, Fang et al. has reported that a polar chlorine-terminated SASM can modulate the energy-level alignment by forming a dipole moment at the interface. [27] Chen et al. has regulated the crystalline process and optimized the morphology of perovskite film by using 3-aminopropanioc acid SASM modified titanium oxide. [28] Other SASMs with different chemical terminations (such as amines, [29] carboxylates, [30] thiols, [31] and phosphonic acid [32] ) are also demonstrated to dramatically modify the electron Interfacial lattice mismatch and adverse reaction are the key issues hindering the development of nickel oxide (NiO x )-based inverted perovskite solar cells (PVSCs). Herein, a p-chlorobenzenesulfonic acid (CBSA) self-assembled small-molecule (SASM) is adopted to anchor NiO x and perovskite crystals to endow dual-passivation. The chlorine terminal of SASMs can provide growth sites for perovskite, leading to interfacial strain release. Meanwhile, the sulfonic acid group from SASMs can passivate surface defects of NiO x ,...

NiOx Nanocrystals with Tunable Size and Energy Levels for Efficient and UV Stable Perovskite Solar Cells

“…First, it is due to the Ni 3+ induced redox reaction at the NiO x /perovskite interface, such a phenomenon has been widely reported in literatures. [26,28,29,35] Second, it could be due to the direct damage of the perovskite by UV light. Though the NiO x film could absorb part of the UV light, it is unlikely to filter all of them due to the limited film thickness.…”

“…Among them, NiO x has been mostly studied for planar inverted devices for the advantages of low cost, suitable energy band structure, good transparency, and strong electron blocking capability. [21,[25][26][27][28][29][30][31][32][33][34][35][36] As indicated by its chemical formula, the NiO x is nonstoichiometric and usually composed of NiO, Ni 2 O 3 , and even NiOOH. The presence of Ni 3+ plays a contradictory role in determining the performance of NiO x in PSCs.…”

Highly Improved Efficiency and Stability of 2D Perovskite Solar Cells via Bifunctional Inorganic Salt KPF6 Modified NiOx Hole Transport Layer

“…In general, the increase of the Ni 3+ /Ni 2+ ratio contributes to the improvement of the conductivity of NiO x . [ 35 ] This result shows that NiO x /KPF 6 film has better electrical conductivity. In addition, the devices composed of FTO/HTLs/Ag were prepared to investigate the conductivity of the NiO x and NiO x /KPF 6 films.…”

“…Figure 2c shows that 2D perovskite deposited on the NiO x /KPF 6 substrate has a lower PL intensity compared to the bare NiO x , indicating faster extraction of carriers from perovskite by HTL. [ 38 ] Furthermore, Figure 2d shows that the average carrier lifetime (τ ave ) of the FTO/NiO x /KPF 6 /PVK sample (8.29 ns) is less than one‐third that of the FTO/NiO x /PVK sample (29.23 ns). It shows that the insertion of KPF 6 between NiO x and perovskite promotes the transfer of hole carriers and observably decreases the energy loss at the NiO x /PVK interface.…”

“…[ 46 ] Therefore, the results in Figure 4d and S4, Supporting Information reveal that the KPF 6 ‐modified layer effectively suppresses defect‐induced carrier recombination between NiO x and 2D perovskite. [ 38 ]…”