Tungsten doped indium oxide (In2O3: W, IWO) thin films have been attracting increasing attention due to their excellent optoelectronic properties. Here, a series of IWO thin films were prepared using direct current (DC) magnetron sputtering method, by varying the sputtering pressure. Analysis revealed that the IWO films prepared under sputtering pressure of 0.4 Pa exhibited excellent optoelectronic performance, with low square resistance, resistivity, high carrier concentration and mobility. The resulting semi-transparent perovskite solar cells (ST-PSCs), with IWO fabricated under 0.4 Pa, yield a PCE of 15.71% for the large area modules of 100 cm2 (active area 64.8 cm2).

Vacuum deposition is promising for large-area, high-throughput production of perovskite solar cells (PSCs). However, the strict low humidity control increases the costs for manufacturing facilities and hinders the large-scale production of PSCs. In this work, a sequential deposition method was used to prepare the perovskite intermediate phase, and the impact of ambient humidity was studied during the annealing process. It is shown that proper humidity has a positive effect on the perovskite layer, which is conducive to accelerate the reaction between organic salts and PbI2 and improve the surface morphology of the film. The perovskite annealing under 55% relative humidity exhibits fewer defects and faster carrier transport kinetics. The resulting PSCs, with all layers fabricated adopting vapor deposition, yield a power conversion efficiency (PCE) of 15.01% for the large area modules of 100 cm2 (active area 64.8 cm2). More impressively, the PCE of the unpackaged cell modules remained above 80% after being placed in ambient air for 1200 h. The results open a promising way for scalable fabrication of humidity-tolerant large-area perovskite solar cell modules and shed light on the industrial production of PSCs.

A considerable efficiency gap exists between large-area perovskite solar modules and small-area perovskite solar cells. The control of forming uniform and large-area film and perovskite crystallization is still the main obstacle restricting the efficiency of PSMs. In this work, we adopted a solid–liquid two-step film formation technique, which involved the evaporation of a lead iodide film and blade coating of an organic ammonium halide solution to prepare perovskite films. This method possesses the advantages of integrating vapor deposition and solution methods, which could apply to substrates with different roughness and avoid using toxic solvents to achieve a more uniform, large-area perovskite film. Furthermore, modification of the NiO x /perovskite buried interface and introduction of Urea additives were utilized to reduce interface recombination and regulate perovskite crystallization. As a result, a large-area perovskite film possessing larger grains, fewer pinholes, and reduced defects could be achieved. The inverted PSM with an active area of 61.56 cm 2 (10 × 10 cm 2 substrate) achieved a champion power conversion efficiency of 20.56% and significantly improved stability. This method suggests an innovative approach to resolving the uniformity issue associated with large-area film fabrication.

Wide‐bandgap (WBG) perovskite solar cells (PSCs) have garnered significant attention for their potential applications in tandem solar cells. However, their large open‐circuit voltage ( V OC ) deficit and serious photo‐induced halide segregation remain the main challenges that impede their applications. Herein, a post‐treatment strategy without thermal annealing is presented to form a 2D top layer of 2‐thiopheneethylammonium lead halide ( n = 1) on WBG perovskites. This thermal annealing‐free post‐treatment method can more effectively passivate the defects of WBG methylamine (MA)‐free formamidinium/cesium lead iodide/bromide perovskite films and suppress photo‐induced perovskite phase segregation, as compared with the thermal annealing method that yields multi‐2D phases. The resulting opaque and semi‐transparent 1.66 eV‐bandgap perovskite solar cells deliver maximum power conversion efficiencies of 21.47% (a small V OC deficit of 0.43 V) and 19.11%, respectively, both of which are among the highest reports for inverted MA‐free WBG PSCs. Consequently, four‐terminal all‐perovskite tandem cells realize a remarkable efficiency of 26.64%, showing great promise for their applications in efficient multi‐junction tandem solar cells.

Development of suitable hole transport materials is vital for perovskite solar cells (PSCs) to diminish the energy barrier and minimize the potential loss. Here, a low-cost hole transport molecule named SFX-POCCF3 (23.72 $/g) is designed with a spiro[fluorene-9,9'-xanthene] (SFX) core and terminated by trifluoroethoxy units. Benefiting from the suitable energy level, high hole mobility, and better charge extraction and transport, the PSCs based on SFX-POCCF3 exhibit improved open-circuit voltage by 0.02 V, therefore, the PSC device based on SFX-POCCF3 exhibits a champion PCE of 21.48%, which is comparable with the control device of Spiro-OMeTAD (21.39%). More importantly, the SFX-POCCF3 based PSC possesses outstanding light stability, which retains 95% of the initial efficiency after about 1,000 h continuous light soaking, which is in accordance with the result continuous output at maximum power point. Whereas, Spiro-OMeTAD witnesses a rapid decrease to 80% of its original efficiency after 100 h light soaking. This work demonstrated that an efficient alignment of energy levels between HTL and perovskite will lead to significant highly efficient PSCs with remarkably enhanced light stability.

GlyCl passivates the defects of narrow-bandgap Pb–Sn perovskites from bottom to up, boosting the solar cell efficiency from 14.28% to 22.07%.

All-perovskite tandem solar cells hold great promise in surpassing the Shockley–Queisser limit for single-junction solar cells 1 – 3 . However, the practical use of these cells is currently hampered by the subpar performance and stability issues associated with mixed tin–lead (Sn–Pb) narrow-bandgap perovskite subcells in all-perovskite tandems 4 – 7 . In this study, we focus on the narrow-bandgap subcells and develop an all-in-one doping strategy for them. We introduce aspartate hydrochloride (AspCl) into both the bottom poly(3,4-ethylene dioxythiophene)–poly(styrene sulfonate) and bulk perovskite layers, followed by another AspCl posttreatment. We show that a single AspCl additive can effectively passivate defects, reduce Sn 4+ impurities and shift the Fermi energy level. Additionally, the strong molecular bonding of AspCl–Sn/Pb iodide and AspCl–AspCl can strengthen the structure and thereby improve the stability of Sn–Pb perovskites. Ultimately, the implementation of AspCl doping in Sn–Pb perovskite solar cells yielded power conversion efficiencies of 22.46% for single-junction cells and 27.84% (27.62% stabilized and 27.34% certified) for tandems with 95% retention after being stored in an N 2 -filled glovebox for 2,000 h. These results suggest that all-in-one AspCl doping is a favourable strategy for enhancing the efficiency and stability of single-junction Sn–Pb perovskite solar cells and their tandems.

CuI hole transporter-based perovskite solar cells (PSCs) are prepared via a low-temperature in situ deposition method. As demonstrated, the results of x-ray diffraction indicate that the CuI hole-transporter has been fabricated successfully and obtained a better stability, and this can be supported by corresponding scanning electron microscopy, including the dense surface and clear cross section. Furthermore, a maximum incident photon-to-electron conversion efficiency (IPCE) of ∼16.78% is obtained at the CuI-based PSC cell with 2nd time deposition, which can be mainly attributed to the fact that, with the fewer defects in the high-quality interface and matched potential structure for promoting carrier interface immigration/diffusion, the CuI-based hole-transporter exhibits decent hole-extraction to make photo-generated electron/holes have a matched mobility. The remaining PbI 2 , with a better passivation, can inhibit carrier recombination, and both can improve the IPCE efficiently. Therefore, this lower cost and easily controlled technique is suitable for large-scale solar cells.

Narrow-bandgap (NBG) mixed tin/lead-based (Sn-Pb) perovskite solar cells (PSCs) have attracted extensive attention for use in tandem solar cells. However, they are still plagued by serious carrier recombination due to inferior film properties resulting from the alloying of Sn with Pb elements, which leads to p-type self-doping behaviors. This work reports an effective tin oxide (SnOx ) doping strategy to produce high-quality Sn-Pb perovskite films for utilization in efficient single-junction and tandem PSCs. SnOx can be naturally oxidized from tin diiodide raw powders and successfully incorporated into Sn-Pb perovskite films. Consequently, Sn-Pb perovskite films doped with SnOx exhibit dramatically improved morphology, crystallization, absorption, and more interestingly, upward-shifted Fermi levels. The resulting narrow-bandgap Sn-Pb PSCs with natural SnOx doping have considerably reduced carrier recombination, therefore delivering a maximum power conversion efficiency (PCE) of 22.16% for single-junction cells and a remarkable PCE of 26.01% (with a steady-state efficiency of 25.33%) for two-terminal all-perovskite tandem cells. This work introduces a facile doping strategy for the manufacture of efficient single-junction narrow-bandgap PSCs and their tandem solar cells.

Mixed lead and tin (Pb-Sn) halide perovskites promise high-performance solar cells because of their narrow bandgaps and other outstanding essential properties. However, there is still a big gap between the performance of the practical devices and theoretical limitations. Here we investigate key factors for realizing high-performance narrow-bandgap Pb-Sn perovskite solar cells (PSCs) via numerical simulations. We first study the effects of extrinsic factors on device performance, which predicts that a p-i-n structure along with appropriate charge transport layers is superior to an n-i-p structure, benefiting from a better energy band alignment. We further investigate key intrinsic factors and demonstrate that surface defect density, body defect density, and film thickness of perovskite absorbers play a pivotal role in determining device performance. The simulation results imply that narrow-bandgap Pb-Sn PSCs with fully-powered optimization should be able to realize a power conversion efficiency of 28.56%. Motivated by the simulations, we also successfully fabricate efficient narrow-bandgap Pb-Sn single-junction and 4-terminal all-perovskite tandem PSCs, which deliver high efficiencies of 21.01% and 26.01% measured under reverse voltage scans, respectively. This work points the way toward the improvement of narrow-bandgap Pb-Sn PSCs in the future.

Tin halide perovskite solar cells (TPSCs) have attracted extensive attention because of their low toxicity and high theoretical efficiency. However, rapid crystallization, rich defects, and easy oxidation of tin‐based perovskite films seriously restrict solar cell performance. Herein, a composition and additive engineering solution by removing commonly used tin fluoride additive from formamidinium tin triiodide perovskite precursors and replacing it with excess tin (II) iodide and ethylenediamine dihydroiodide (EDAI 2 ) is adopted. The presence of EDAI 2 and excess SnI 2 and the absence of SnF 2 enable tin‐based perovskite films with greatly improved morphology, enhanced crystalline quality, boosted optical properties, and prolonged carrier lifetime. Therefore, the SnF 2 ‐free non‐stoichiometric TPSCs employing the EDAI 2 additive and excess SnI 2 have increased built‐in potential, lowered dark currents, and reduced carrier recombination. The resulting SnF 2 ‐free and SnI 2 ‐rich TPSCs with EDAI 2 addition realize a steady‐state efficiency of 10.0%, which is one of the highest power conversion efficiencies among the SnF 2 ‐free TPSCs, along with considerably improved light stability. This work highlights the crucial roles of additives in TPSCs and provides an effective strategy to fabricate efficient and stable low‐toxic lead‐free perovskite solar cells.

Residual lattice strain in halide perovskites has been recognized as a key factor that affects device efficiency and stability of perovskite solar cells (PSCs). Here, we reveal that the escape of organic ammonium halide and their inhomogeneous distribution after thermal annealing could cause severe residual strain in intrinsic thermal stable formamidinium-cesium (FACs) perovskite films. Thus, we develop an imprint-assisted organic ammonium halide compensation strategy for residual lattice strain relaxation. We demonstrate the residual lattice strain is well-released after post-treatment, along with further perovskite grain growth/coalescence, crystallinity improve-ment, and defect repair. As a result, the strain-free PSCs with nickel oxide based inverted architecture exhibit a power conversion efficiency as high as 21.30% and the corresponding encapsulated devices retain 98% of their initial efficiencies at 45 degrees C under 1-sun equivalent white-light light-emitting diode array illumination with maximum power point tracking in the ambient environment for 1000 h.

Perovskite solar cells have emerged as one of the most promising thin-film photovoltaic (PV) technologies and have made a strong debut in the PV field. However, they still face difficulties with up-scaling to module-level devices and long-term stability issue. Here, we report the use of a room-temperature nonvolatile Lewis base additive, diphenyl sulfoxide(DPSO), in formamidinium-cesium (FACs) perovskite precursor solution to enhance the nucleation barrier and stabilize the wet precursor film for the scalable fabrication of uniform, large-area FACs perovskite films. With a parallel-interconnected module design, the resultant solar module realized a certified quasi-stabilized efficiency of 16.63% with an active area of 20.77 cm2 The encapsulated modules maintained 97 and 95% of their initial efficiencies after 10,000 and 1187 hours under day/night cycling and 1-sun equivalent white-light light-emitting diode array illumination with maximum power point tracking at 50°C, respectively.

Organic light emitting diodes (OLEDs) employing organic thin‐film based emitters have attracted tremendous attention due to their widespread applications in lighting and as displays in mobile devices and televisions. The novel thin‐film photovoltaic techniques using organic or organic–inorganic hybrid materials such as organic photovoltaics (OPVs) and perovskite solar cells (PSCs) have become emerging competitive candidates with regard to the traditional photovoltaic techniques on account of high‐efficiency, low‐cost, and simple manufacturing processing properties. However, OLEDs, OPVs, and PSCs are vulnerable to the undesired degradation induced by moisture and oxygen. To afford long‐term stability, a robust encapsulation technique by employing materials and structures that possess high barrier performance against oxygen and moisture must be explored and employed to protect these devices. Herein, the recent progress on specific encapsulation materials and techniques for three types of devices on the basis of fundamental understanding of device stability is reviewed. First, their degradation mechanisms, as well as, influencing factors are discussed. Then, the encapsulation technologies and materials are classified and discussed. Moreover, the advantages and disadvantages of various encapsulation technologies and materials coupled with their encapsulation applications in different devices are compared. Finally, the ongoing challenges and future perspectives of encapsulation frontier are provided.

Perovskite solar cells (PSCs) have attracted much attention in the past decade and their power conversion efficiency has been rapidly increasing to 25.2%, which is comparable with commercialized solar cells. Currently, the long-term stability of PSCs remains as a major bottleneck impeding their future commercial applications. Beyond strengthening the perovskite layer itself and developing robust external device encapsulation/packaging technology, integration of effective barriers into PSCs has been recognized to be of equal importance to improve the whole device's long-term stability. These barriers can not only shield the critical perovskite layer and other functional layers from external detrimental factors such as heat, light, and H2O/O-2, but also prevent the undesired ion/molecular diffusion/volatilization from perovskite. In addition, some delicate barrier designs can simultaneously improve the efficiency and stability. In this review article, the research progress on barrier designs in PSCs for improving their long-term stability is reviewed in terms of the barrier functions, locations in PSCs, and material characteristics. Regarding specific barriers, their preparation methods, chemical/photoelectronic/mechanical properties, and their role in device stability, are further discussed. On the basis of these accumulative efforts, predictions for the further development of effective barriers in PSCs are provided at the end of this review.

In article number 2001610, Zonghao Liu, Liyuan Han, Wei Chen and co-workers, review the stability improvement strategy of perovskite solar cells from the view point of barrier designs. The barriers can address adverse issues like product volatilization, ion diffusion, electrode corrosion, and fight off the harmful influence of external stresses including sunlight, heat, H2O/O2, electric bias, etc.

Much less additive content of 0.5% CaI2 instead of 5% PbI2 was incorporated into the CH3NH3PbI3 film and a dense and surface-smooth morphology was obtained with much enlarged crystal grains. The champion PSC based on MAPbI3(CaI2)0.005 layer demonstrated a very high PCE of 19.3% with superior long-term stability.

A power conversion efficiency of 17.9% has been obtained for the device with a critical BCP thickness of 5 nm. While if the BCP layer is too thin or too thick, charge accumulation will emerge and lead to device performance degradation.