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Surface defects cause non‐radiative charge recombination and reduce the photovoltaic performance of perovskite solar cells (PSCs), thus effective passivation of defects has become a crucial method for achieving efficient and stable devices. Organic ammonium halides have been widely used for perovskite surface passivation, due to their simple preparation, lattice matching with perovskite, and high defects passivation ability. Herein, a surface passivator 2,4,6‐trimethylbenzenaminium iodide (TMBAI) is employed as the interfacial layer between the spiro‐OMeTAD and perovskite layer to modify the surface defect states. It is found that TMBAI treatment suppresses the nonradiative charge carrier recombination, resulting in a 60 mV increase of the open‐circuit voltage (Voc) (from 1.11 to 1.17 V) and raises the fill factor from 76.3% to 80.3%. As a result, the TMBAI‐based PSCs device demonstrates a power conversion efficiency (PCE) of 23.7%. Remarkably, PSCs with an aperture area of 1 square centimeter produce a PCE of 21.7% under standard AM1.5 G sunlight. The unencapsulated TMBAI‐modified device retains 92.6% and 90.1% of the initial values after 1000 and 550 h under ambient conditions (humidity 55%–65%) and one‐sun continuous illumination, respectively. [ABSTRACT FROM AUTHOR]

Perovskite-based triboelectric nanogenerators (TENGs) have obtained wide attention and investigation due to their excellent dielectric and electrical properties, as well as the diversity of perovskite materials. In this work, phenethyl ammonium iodide (PEAI) was applied to tailor the interface of MAPbI3 films, to form a 2D/3D heterojunction, and to passivate defects of films. The TENGs after PEAI passivation achieved significant improvement in voltage and current density with an increase in the output voltage from 33.3 to 40.1 V, and the current density was improved from 9.1 to 10.1 mA/m2. The improved output properties might be attributed to changes in the triboelectric charge density, carrier mobility, reduced interfacial combination by effective defect passivation, and favorable charge transporting by constructing 2D/3D heterojunctions for the effect of the built-in electric field. This work demonstrates that interfacial modification is one of the feasible methods for improving the performance of TENGs and supplies further possibilities for high-performance perovskite-based TENGs. [ABSTRACT FROM AUTHOR]

The photovoltaic performance of perovskite solar cells (PSCs) prepared by the low‐temperature solution method has made rapid progress. However, the surface of the film is prone to defects that trap photogenerated charges, resulting in nonradiative recombination energy loss and limiting the open‐circuit voltage and overall performance of the device. Interface passivation as an effective method can significantly reduce defects and inhibit nonradiative recombination. Herein, a simple method is introduced to passivate perovskite films by a carboxylated (–COOH) sensitizer that is applied in dye‐sensitized solar cells (DSCs), 4‐(bis(9,9‐dimethyl‐9H‐flouren‐2‐yl)amino)‐1‐naphthoic acid (KTN) molecules. The research results show that the chemical interaction between KTN and iodide vacancies exposing Pb2+ can reduce the nonradiative recombination and elongate the carrier lifetime, which leads to an excellent power conversion efficiency (PCE) with 23% with an obvious increase in open‐circuit voltage (VOC) of 60 mV. Moreover, the defect passivation can significantly enhance the stability of corresponding PSC devices. The unencapsulated device with KTN passivation can readily maintain ≈90% of its initial efficiency value after 1400 h. These findings may provide a novel approach for interfacial defect passivation to further promote the performance and stability of PSCs. [ABSTRACT FROM AUTHOR]

In lead halide perovskite solar cells (PSCs), the valence band maximum of NiO x matches well with that of MAPbI 3 or FAPbI 3 , while its conduction band minimum is much higher than that of the perovskite materials. Consequently, it can serve the function of hole transport layers (HTL), as well as light-in window of p-i-n inverted planar PSCs owing to its large band gap of 3.7 eV. In this work, MAPbI 3 and mixed cation FA 0.85 MA 0.15 Pb(Br 0.15 I 0.85 ) 3 devices with room temperature solution processed NiO x as HTL were fabricated in a typical device structure of “ITO ⧹ NiO x ⧹ Perovskites ⧹ PC 61 BM ⧹ Zirconium (IV) Acetylacetonate ⧹ Ag”. Both kinds of devices exhibit excellent performance with a champion cells conversion efficiency of 19.45% and 17.77% for the FAMA and the pure MA, respectively. The hole extraction ability of NiO x as HTLs was extensively characterized by different techniques, and it was confirmed that room temperature solution processed NiO x serves as an excellent HTL in the inverted planar PSCs. [ABSTRACT FROM AUTHOR]

Abstract: High‐quality hole transport layers are prepared by spin‐coating copper doped nickel oxide (Cu:NiO) nanoparticle inks at room temperature without further processing. In agreement with theoretical calculations predicting that Cu doping results in acceptor energy levels closer to the valence band maximum compared to gap states of nickel vacancies in undoped NiO, an increase in the conductivity in Cu:NiO films compared to NiO is observed. Cu in Cu:NiO can be found in both Cu+ and Cu2+ states, and the substitution of Ni2+ with Cu+ contributes to both increased carrier concentration and carrier mobility. In addition, the films exhibit increased work function, which together with the conductivity increase, enables improved charge transfer and extraction. Furthermore, recombination losses due to lower monomolecular Shockley‐Read‐Hall recombination are reduced. These factors result in an improvement of all photovoltaic performance parameters and consequently an increased efficiency of the inverted planar perovskite solar cells. A power conversion efficiency (PCE) exceeding 20% could be achieved for small‐area devices, while PCE values of 17.41 and 18.07% are obtained for flexible devices and large area (1 cm2) devices on rigid substrates, respectively. [ABSTRACT FROM AUTHOR]

PEACl is employed to treat the pristine FASnI 3 film, leading to forming an ultrathin low-dimensional perovskite layer at the interface of perovskite and adjacent transporting layer. Finally, the treatment results in the enhanced stability and conversion efficiency from 9.40% to 11.63% by improving the crystallinity and interface, suppressing Sn2+ oxidation, decreasing defect density and well-matched energy level. [Display omitted] • PEACl is used for forming an ultrathin low dimensional perovskite layer at the interface of FASnI 3 perovskite and PCBM layer. • The effective suppression of Sn2+ oxidation, the improved band level alignment and the decrease of the surface defect density is achieved by the PEACl treatment. • Significantly enhanced conversion efficiency of tin-based PSCs can be obtained from 9.40% to 11.63% by the PEACl treatment. Environment friendly tin perovskite solar cells (TPSCs) have become a promising candidate due to their low toxicity and similar electronic configuration to lead counterparts. However, the easily generated defects due to the Sn2+oxidation and poor morphology originated from rapid crystallization are both barriers for tin-based devices in the enhancement of photovoltaic performance. Here, phenethylammonium chloride (PEACl) is introduced for post-treating FASnI 3 films, which plays dual roles in adjusting film topography and passivating defects in bulk and interface of films. First, the film morphology can be improved by eliminating SnF 2 impurities. In addition, a small amount of two-dimension perovskite can be formed in the films, inducing preferred orientation in secondary crystallization, well-matched energy level, and effective defect passivation. Finally, the FASnI 3 -based devices with PEACl treatment obtained a champion conversion efficiency of 11.63% with an average value of 10.76%, along with the obvious enhanced open circuit voltage and fill factor. In contrast, the pristine FASnI 3 devices range from 6.92% to 9.40% with an average value of 7.96%. This work not only deepens our understanding of the suppression of defects in tin-based perovskites but also paves a facile way to ameliorate film morphology and interfaces to fabricate promising tin perovskites and devices. [ABSTRACT FROM AUTHOR]

• The power conversion efficiency of HBPC passivated perovskite solar cells reaches up to 22%. • The operational stability of the corresponding devices is substantially improved. • HBPC is successfully employed into perovskite photovoltaic devices as effective interface passivators. The organic–inorganic hybrid perovskite solar cells (PSCs) achieve relatively high power conversion efficiencies (PCEs) over the past few years. However, defects on the surface and at the grain boundaries of the perovskite active layers are critical factors in ensuing perovskite devices. It is still a huge challenge to imminent the commercial use of this technology by passivating the defects of perovskite materials and corresponding interfaces. Here, we employ the HBPC ((4′-pentyl-[1,1′-biphenyl]-4-yl)methanaminium iodide) interface passivation strategy to prepare high-quality perovskite surfaces, which can significantly improve the efficiency and stability of PSCs. As compared to control cell (20.0%), the HBPC-passivated perovskite device achieves a champion PCE of 22.07% with less hysteresis. The obtained results show that the presence of HBPC on the perovskite film can reduce the charge trap density and extend the carrier recombination life, thereby boosting the performance of perovskite devices, leading a great promise in the pursuit of high-efficiency and stable PSCs. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) are the most promising substitute for silicon-based solar cells. However, their power conversion efficiency and stability must be improved. The recombination probability of the photogenerated carriers at each interface in a PSC is much greater than that of the bulk phase. The interface of a perovskite polycrystalline film is considered to be a defect-rich area, which is the main factor limiting the efficiency of a PSC. This review introduces and summarizes practical interface engineering techniques for improving the efficiency and stability of organic–inorganic lead halide PSCs. First, the effect of defects at the interface of the PSCs, the energy level alignment, and the chemical reactions on the efficiency of a PSC are summarized. Subsequently, the latest developments pertaining to a modification of the perovskite layers with different materials are discussed. Finally, the prospect of achieving an efficient PSC with long-term stability through the use of interface engineering is presented. [ABSTRACT FROM AUTHOR]

Grain boundaries in lead halide perovskite films lead to increased recombination losses and decreased device stability under illumination due to defect‐mediated ion migration. The effect of a conjugated polymer additive, poly(bithiophene imide) (PBTI), is investigated in the antisolvent treatment step in the perovskite film deposition by comprehensive characterization of perovskite film properties and the performance of inverted planar perovskite solar cells (PSCs). PBTI is found to be incorporated within grain boundaries, which results in an improvement in perovskite film crystallinity and reduced defects. The successful defect passivation by PBTI yields reduces recombination losses and consequently increases power conversion efficiency (PCE). In addition, it gives rise to improved photoluminescence stability and improved PSC stability under illumination which can be attributed to reduced ion migration. The optimal devices exhibit a PCE of 20.67% compared to 18.89% of control devices without PBTI, while they retain over 70% of the initial efficiency after 600 h under 1 sun illumination compared to 56% for the control devices. [ABSTRACT FROM AUTHOR]

In this work, significant suppression of the interfacial recombination by facile alkali chloride interface modification of the NiOx hole transport layer in inverted planar perovskite solar cells is achieved. Experimental and theoretical results reveal that the alkali chloride interface modification results in improved ordering of the perovskite films, which in turn reduces defect/trap density, causing reduced interfacial recombination. This leads to a significant improvement in the open‐circuit voltage from 1.07 eV for pristine NiOx to 1.15 eV for KCl‐treated NiOx, resulting in a power conversion efficiency approaching 21%. Furthermore, the suppression of the ion diffusion in the devices is observed, as evidenced by stable photoluminescence (PL) under illumination and high PL quantum efficiency with alkali chloride treatment, as opposed to the luminescence enhancement and low PL quantum efficiency observed for perovskite on pristine NiOx. The suppressed ion diffusion is also consistent with improved stability of the devices with KCl‐treated NiOx. Thus, it is demonstrated that a simple interfacial modification is an effective method to not only suppress interfacial recombination but also to suppress ion migration in the layers deposited on the modified interface due to improved interface ordering and reduced defect density. [ABSTRACT FROM AUTHOR]

The environmentally friendly additive 2,2,2‐trifluoroethylamine hydrochloride (TFEACl) is used in synergy with SnF2 to enhance the efficiency and stability of FASnI3‐based solar cells. Both TFEA+ and Cl− are present in the films, but only Cl− is incorporated into the crystal lattice of the perovskite. The addition of TFEACl suppresses the segregation of SnF2, resulting in improvements in film morphology, in addition to a more favorable energy band alignment, and improved suppression of the formation of Sn4+. Consequently, reduced charge recombination and improved charge collection result in an efficiency enhancement from 3.63 to 5.30%. The stability of the devices is also significantly enhanced, with devices with TFEACl retaining over 60% of initial PCE after 350 h of light soaking in ambient, while devices without TFEACl experience failure in 120 h under the same testing condition. Environmentally friendly 2,2,2‐trifluoroethylamine hydrochloride (TFEACl) is used in synergy with SnF2 to enhance the efficiency and stability of FASnI3‐based solar cells, due to the improvements in film quality, suppression of the Sn2+ oxidation and more favorable energy band alignment. [ABSTRACT FROM AUTHOR]

Although a compact holes-transport-layer (HTL) film has always been deemed mandatory for perovskite solar cells (PSCs), the impact their compactness on the device performance has rarely been studied in detail. In this work, based on a device structure of FTO/CIGS/perovskite/PCBM/ZrAcac/Ag, that effect was systematically investigated with respect to device performance along with photo-physics characterization tools. Depending on spin-coating speed, the grain size and coverage ratio of those CIGS films on FTO substrates can be tuned, and this can result in different hole transfer efficiencies at the anode interface. At a speed of 4000 r.p.m., the band level offset between the perovskite and CIGS modified FTO was reduced to a minimum of 0.02 eV, leading to the best device performance, with conversion efficiency of 15.16% and open-circuit voltage of 1.04 V, along with the suppression of hysteresis. We believe that the balance of grain size and coverage ratio of CIGS interlayers can be tuned to an optimal point in the competition between carrier transport and recombination at the interface based on the proposed mechanism. This paper definitely deepens our understanding of the hole transfer mechanism at the interface of PSC devices, and facilitates future design of high-performance devices. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have been intensively investigated over the last several years. Unprecedented progress has been made in improving their power conversion efficiency; however, the stability of perovskite materials and devices remains a major obstacle for the future commercialization of PSCs. In this review, recent progress in PSCs is summarized in terms of the hybridization of compositions and device architectures for PSCs, with special attention paid to device stability. A brief history of the development of PSCs is given, and their chemical structures, optoelectronic properties, and the different types of device architectures are discussed. Then, perovskite composition engineering is reviewed in detail, with particular emphasis on the cationic components and their impact on film morphology, the optoelectronic properties, device performance, and stability. In addition, the impact of two-dimensional and/or one-dimensional and nanostructured perovskites on structural and device stability is surveyed. Finally, a future outlook is proposed for potential resolutions to overcome the current issues. [ABSTRACT FROM AUTHOR]