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Carbon-based perovskite solar cells (c-PSCs) have attracted increasing attention due to their numerous advantages including ease of fabrication, the potential of assembling flexible devices, low manufacturing costs as well as large-scale production. However, c-PSCs suffer from the limited hole extraction and high charge carrier recombination due to the inadequate interface contact between the carbon electrode and perovskite film. Herein, we report the fabrication of planar c-PSCs with high efficiency and excellent stability by employing electrochemically produced large-area phosphorene flakes as a hole-transporting layer (HTL). Large-area phosphorene shows well-aligned band energy levels with the perovskite, and thus led to the efficient hole extraction and the reduced hysteresis behaviour. Consequently, while exhibiting excellent stability under various harsh testing conditions, the devices with phosphorene HTL delivered a power conversion efficiency of over 15% with an open-circuit voltage of 1.082 V, which is the highest reported value for c-PSCs without traditional hole transporting materials to date. [ABSTRACT FROM AUTHOR]

Semitransparent perovskite solar cells (ST‐PSCs) hold significant appeal for various applications in smart windows, multijunction tandem devices, bifacial and chargeable devices, etc. Unfortunately, to possess high transparency, the perovskite layer in the ST‐PSCs must be kept relatively thin (<400 nm), which in turn causes insufficient light absorption and thus inferior device performance. Herein, a 2D perovskite nanoplatelets (NPLs)/poly(methyl methacrylate) (PMMA) composite thin layer is applied in the ST‐PSCs to solve these problems. Thanks to its dual function of down‐conversion (DC) effect, converting high‐energy UV photons into low‐energy visible photons to enhance the photocurrent, and interfacial passivation, reducing the nonradiative recombination at the interface, the 2D NPLs–PMMA‐based devices with the different average visible transmittance (AVT) values of perovskite film demonstrate significantly improved power‐conversion efficiency (PCE) compared to the pristine devices, and remarkable UV stability, retaining over 77% of initial PCE after aging under continuous UV illumination for 280 h. More importantly, the full bifacial ST‐PSCs using a transparent MoO3/Au/MoO3 rear electrode exhibits a record PCE of 14.26% and 10.65% with a whole device AVT of 19.4% and 26.9%, respectively, which are among the highest performing ST‐PSCs of the kind reported to date. [ABSTRACT FROM AUTHOR]

The facile synthesis and beneficial properties of tin oxide have driven the development of efficient planar perovskite solar cells (PSCs). To increase the PSC performance, alkali salts are used to treat the SnO2 surface to minimize the defect states. However, the underlying mechanism of alkali cations' role in the PSCs needs further exploration. Herein the effect of alkali fluoride salts (KF, RbF, and CsF) on the properties of SnO2 and PSC performance is investigated. The results show different alkali have significant roles depending on their nature. Larger cations Cs+ preferably locate at the SnO2 film surface to passivate surface defects and enhance conductivity, while smaller cations like Rb+ or K+ cations tend to diffuse into the perovskite layer to reduce trap density of the material. The former effect leads to enhanced fill factor while the latter effect increases the open circuit voltage of the device. It is then demonstrated that a dual cation post‐treatment of the SnO2 layer with RbF and CsF achieves PSC with a significantly higher power conversion efficiency (PCE) of 21.66% compared to pristine PSC with a PCE of 19.71%. This highlights the significance of defect engineering of SnO2 using selective multiple alkali treatment to improve PSC performance. [ABSTRACT FROM AUTHOR]

Carbon electrode‐based perovskite solar cells (C‐PSCs) exhibit a promising future for commercialization, due to their low cost, facile fabrication, and mass production potential. However, compared with metal‐based counter electrodes, carbon electrodes (CEs) often suffer from relatively low electrical conductivity, porous and rough morphology leading to poor interfacial contact with the underneath layer thereby restricting the power conversion efficiency (PCE) of C‐PSCs. Herein, a simple approach is presented to prepare liquid metal/carbon composite electrodes by uniformly dispersing liquid gallium droplets into CEs to enhance both the electrical conductivity and interfacial contact between carbon and the adjacent layer. Compared to control devices without Ga, the Ga‐embedded carbon also creates a more favorable energy band alignment with the hole transport layer underneath for efficient hole transport, thus suppressing recombination at the interfaces. By optimizing the weight ratio between Ga and the carbon paste, the corresponding C‐PSCs deliver an optimum PCE of 13.99% with a higher fill factor (68.95%) compared to pristine C‐PSCs (PCE = 13.13%). In addition, the Ga‐containing devices demonstrate reinforced thermal stability with 65% efficiency retention after 1800 min under a thermal stress of 80 °C without encapsulation. [ABSTRACT FROM AUTHOR]

Highlights: A rational design of metal halide perovskites for achieving efficient CO2 reduction reaction was demonstrated. The stability of CsPbI3 perovskite nanocrystal (NCs) in aqueous electrolyte was improved by compositing with reduced graphene oxide (rGO). The CsPbI3/rGO catalyst exhibited > 92% Faradaic efficiency toward formate production with high current density which was associated with the synergistic effects between the CsPbI3 NCs and rGO. Transformation of greenhouse gas (CO2) into valuable chemicals and fuels is a promising route to address the global issues of climate change and the energy crisis. Metal halide perovskite catalysts have shown their potential in promoting CO2 reduction reaction (CO2RR), however, their low phase stability has limited their application perspective. Herein, we present a reduced graphene oxide (rGO) wrapped CsPbI3 perovskite nanocrystal (NC) CO2RR catalyst (CsPbI3/rGO), demonstrating enhanced stability in the aqueous electrolyte. The CsPbI3/rGO catalyst exhibited > 92% Faradaic efficiency toward formate production at a CO2RR current density of ~ 12.7 mA cm−2. Comprehensive characterizations revealed the superior performance of the CsPbI3/rGO catalyst originated from the synergistic effects between the CsPbI3 NCs and rGO, i.e., rGO stabilized the α-CsPbI3 phase and tuned the charge distribution, thus lowered the energy barrier for the protonation process and the formation of *HCOO intermediate, which resulted in high CO2RR selectivity toward formate. This work shows a promising strategy to rationally design robust metal halide perovskites for achieving efficient CO2RR toward valuable fuels. [ABSTRACT FROM AUTHOR]

The article in ChemSusChem discusses a water-based recycling process for the valuable SnO2/FTO substrate used in perovskite solar cells, leading to the creation of high-performance solar cells. This innovative approach aims to increase cost-effectiveness and sustainability in the fabrication of perovskite solar cells. For more details, readers can refer to the Research Article authored by H. Wang and colleagues. [Extracted from the article]

The halide perovskite nanocrystals (P‐NCs) can address a plethora of issues of the light‐emission technologies, due to its low temperature processing. To successfully employ P‐NCs for light‐emitting diodes (LEDs), one needs to resolve the issues of stability of the LEDs. The stability of device can be achieved by charge balance of electrons and holes recombination in active material. To investigate this herein, a self‐assembled carbon dots (CDs) layer is fabricated from waste small strands of human hair. The self‐assembled CDs layer is used beneath P‐NCs layer to reduce the band‐off set for hole transport, thus balancing the electron and holes carrier in active layer. The layer is used as an active light‐emitting layer to fabricate a LED device that exhibits green luminescence of 4800 cd m−2 at a current efficiency of 10.7 cd A−1 and external quantum efficiency of 4.8%. The LED exhibits operational stability of nearly 200 h. The same film is used to demonstrate a flexible device with maximum luminescence of 2259 cd m−2, with a high current density of 474 mA cm−2, current efficiency of 1.37 cd A−1 and a low turn‐on voltage of 3.5 V. All the display devices are measured in air without encapsulation. [ABSTRACT FROM AUTHOR]

Metal halide perovskite materials have demonstrated unique properties for applications in optoelectrical devices such as solar cells, light-emitting diodes and photodetectors. The unprecedented world-record energy conversion efficiency of over 25% achieved with solution-processed perovskite solar cells is escalating research towards the commercialisation of the perovskite materials. Nevertheless, the use of large amounts of hazardous and carcinogenic solvents such as N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and skin-penetrating dimethyl sulfoxide (DMSO) in the current perovskite synthesis protocols are limited for the commercial uptake of perovskite technology as these detrimental solvents can cause environmental, health and safety issues. Therefore, the development of alternative environmentally-friendly, green solvents for the synthesis of perovskite materials including thin films, nanocrystals or single-crystals with desirable properties is critical for the commercialisation of perovskite technologies. In this review, we summarize the research progress of solution-processable perovskite material using low-toxic and green solvent alternatives. We discuss the fundamental properties that need to be considered in screening solvents for the solution processing of metal halide perovskites. By carefully analysing the common features of solvents and anti-solvent systems that have been reported for making perovskite precursor inks for applications in solar cells and light-emitting diodes, we provide insight into the relationship between the solvent molecular ligand – properties of perovskite materials – device performance. We discuss the advantages and challenges of each type of green solvent based on their performance in metal halide perovskite technology, effects on the environment, human health and safety, aiming to provide guidelines towards green metal halide perovskite technology. [ABSTRACT FROM AUTHOR]

Metal halide perovskite nanocrystals (PeNCs) are emerging as one of the most promising materials for optoelectrical devices such as light‐emitting diode (LED) owing to their tunable band gaps, high color purity, and tolerance to defects. Nevertheless, the materials have not yet demonstrated their full potential in practical applications due to the poor stability of PeNCs and their unsatisfactory performance in devices. In this research, LED devices based on CsPbBr3 NCs are successfully demonstrated as an active light‐emitting layer with enhanced efficiency via potassium doping. The study of the effect of potassium dopant on physicochemical properties of inorganic CsPbBr3 PeNCs shows that potassium cations (K+) remain in the crystal structure of perovskite compound as interstitial defects, which results in better coverage of surface ligands on the PeNCs and improved energy band alignment with adjacent electron injection layer (2,2′,2′‐(1,3,5‐benzinetriyl)‐tris(1‐phenyl‐1‐H‐benzimidazole)) and hole injection layer (poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate) in an LED. As a consequence, the green LED with the K‐doped CsPbBr3 PeNCs shows luminance up to 5759 cd m‐2 and external quantum efficiency (EQE) of 5.6%, which is superior to the pristine device without K‐doping (luminance: 4579 cd m‐2, EQE: 4.8%). [ABSTRACT FROM AUTHOR]

Abstract: This work demonstrates the effect of oxygen vacancies in SnOx thin films on the performance of perovskite solar cells. Various SnOx films with different amounts of oxygen vacancies were deposited by sputtering at different substrate temperatures (25–300 °C). The transmittance of the films decreased from 82 to 66 % with increasing deposition temperature from 25 to 300 °C. Both X‐ray photoelectron spectroscopy and electron‐spin resonance spectroscopy confirmed that a higher density of oxygen vacancies was created within the SnOx film at a high substrate temperature, which caused narrowing of the SnOx bandgap from 4.1 (25 °C) to 3.74 eV (250 °C). Combined ultraviolet photoelectron spectroscopy and UV/Vis spectroscopy showed an excellent conduction band position alignment between the methylammonium lead iodide perovskite layer (3.90 eV) and the SnOx electron transport layer deposited at 250 °C (3.92 eV). As a result, a significant enhancement of the open‐circuit voltage from 0.82 to 1.0 V was achieved, resulting in an increase of the power conversion efficiency of the perovskite solar cells from 11 to 14 %. This research demonstrated a facile approach for controlling the amount of oxygen vacancies in SnOx thin films to achieve a desirable energy alignment with the perovskite absorber layer for enhanced device performance. [ABSTRACT FROM AUTHOR]

Abstract: Organic–inorganic lead halide perovskites have shown great future for application in solar cells owing to their exceptional optical and electronic properties. To achieve high‐performance perovskite solar cells, a perovskite light absorbing layer with large grains is desirable in order to minimize grain boundaries and recombination during the operation of the device. Herein, a simple yet efficient approach is developed to synthesize perovskite films consisting of monolithic‐like grains with micrometer size through in situ deposition of octadecylamine functionalized single‐walled carbon nanotubes (ODA‐SWCNTs) onto the surface of the perovskite layer. The ODA‐SWCNTs form a capping layer that controls the evaporation rate of organic solvents in the perovskite film during the postthermal treatment. This favorable morphology in turn dramatically enhances the short‐circuit current density of the perovskite solar cells and almost completely eliminates the hysteresis. A maximum power conversion efficiency of 16.1% is achieved with an ODA‐SWCNT incorporated planar solar cell using (FA0.83MA0.17)0.95Cs0.05Pb(I0.83Br0.17)3 as light absorber. Furthermore, the perovskite solar cells with ODA‐SWCNT demonstrate extraordinary stability with performance retention of 80% after 45 d stability testing under high humidity (60–90%) environment. This work opens up a new avenue for morphology manipulation of perovskite films and enhances the device stability using carbon material. [ABSTRACT FROM AUTHOR]

Density functional theory calculations are performed to study the electronic and optical properties of methylammonium lead/tin iodide perovskites under hydrostatic strain. It is found that the bandgap is significantly reduced to only 80/14 meV in lead/tin iodide perovskites under a moderate −6%/−4% strain. Such bandgap narrowing consequently induces the redshift of light absorption spectrum of the perovskite material by extending the onset light absorption edge by 200 meV. Additionally, applying external strain is also found to lighten the electron effective mass for CH3NH3PbI3/CH3NH3SnI3, thus enhancing the carrier mobility which benefits the collection of photogenerated charge carriers. [ABSTRACT FROM AUTHOR]

Organometal lead halides based perovskite solar cells (PSC) are a recent discovery in photovoltaic technology that have demonstrated impressive power conversion efficiency achieved by cost-effective solution method (e.g. roll-to-roll production) from readily available raw materials. Nevertheless, the PSC devices have shown limited operating life-times due to degradation of the perovskite materials. Since long operational durability is essential for this new and promising PV technology to fulfil its mission to deliver clean, low cost renewable energy, this review presents the most recent research on understanding of the factors that may cause the degradation process in perovskite materials and PSC devices. Strategies that may improve the stability of PSCs through optimization of the device architectures and development of new materials are also discussed. [ABSTRACT FROM AUTHOR]

SCAPS solar cell simulation program was applied to model an inverted structure of perovskite solar cells using Cu-doped Ni 1-x O thin films as hole transport layer. The Cu-doped Ni 1-x O film were made by co-sputtering deposition under different deposition conditions. By increasing the amount of the Cu-dopant, the film crystallinity enhanced whereas the bandgap energy decreased. The transmittance of the thin films decreased significantly by increasing the sputtering power of copper. High quality, uniform, compact, and pin-hole free films with low surface roughness were achieved. The structural, chemical, surface morphology, optical, electrical, and electronic properties of the Cu doped Ni 1-x O films were used as input parameters in the simulation of Pb-based (MAPbI 3-x Cl x) and Pb-free (MAGeI 3) perovskite solar cells. Simulation results showed that the performance of both Pb-based and Pb-free perovskite solar cell devices significantly enhanced with Cu-doped Ni 1-x O film. The highest power conversion efficiency (PCE) for the Pb-free perovskite solar cell is 8.9% which is lower than the highest PCE of 17.5% for the Pb-based perovskite solar cell. [ABSTRACT FROM AUTHOR]

Current–voltage hysteresis of perovskite solar cells (PSCs) has raised the concern of accurate performance measurement in practice. Although various theories have been proposed to elucidate this phenomenon, the origin of hysteresis is still an open question. Herein, the use of guanidinium cation (Gu+)‐dopant is demonstrated to tailor the crystal structure of mixed‐cation formamidinium‐cesium lead triiodide (FA0.83Cs0.17PbI3) perovskite, resulting in an improved energy conversion efficiency and tunable current–voltage hysteresis characteristic in planar solar cells. Particularly, when the concentration of Gu‐dopant for the perovskite film increases, the normal hysteresis initially observed in the pristine PSC is first suppressed with 2%‐Gu‐dopant, then changed to inverted hysteresis with a higher Gu‐dopant. The hysteresis tunability behavior is attributed to the interplay of charge/ion accumulation and recombination at interfaces in the PSC. Furthermore, compared to the cell without Gu+‐dopant, the optimal content of 2% Gu+‐dopant also increases the device efficiency by 14%, reaching over 17% under one sun illumination. A new method to control current–voltage hysteresis of planar structured FA0.83Cs0.17PbI3 perovskite solar cells (PSCs) is presented while enhancing device efficiency through tailoring the crystal structure of the perovskite compound with a guanidinium cation (Gu+)‐dopant. New insights into the correlation of the dynamics of device hysteresis with the interfacial charge recombination and accumulation in the PSCs are revealed. [ABSTRACT FROM AUTHOR]

[Display omitted] Metal halide perovskites (MHPs) with tunable bandgaps and strong light absorptions in the broad spectral range of ∼ 1.2–2.3 eV make them suitable candidates as light absorber in tandem photovoltaic (PV) devices. This review presents the latest progress and limitations of all perovskite tandem solar cells (AP-TSCs) with different configurations. As of today, the power conversion efficiency (PCE) and stability of reported AP-TSCs have not yet met the requirements for commercial products, mainly due to prominent defect activities in both absorbers of top wide bandgap (WB) and bottom narrow bandgap (NB) metal halide perovskites (MHPs). In this paper, we critically examine the unique instabilities and energy loss channels in WB-MHPs and NB-MHPs, as well as discuss the corresponding strategies to suppress them. We also discuss the effect of the interconnecting layer on the preparation of high-quality light absorber by a solution method. Moreover, we analyze in detail the unique requirements and methods of device packaging to improve the stability of AP-TSCs. Finally, we offer new viewpoints on the major challenges, favorable circumstances, and heuristic perspectives for future studies. [ABSTRACT FROM AUTHOR]

Perovskite solar cells using carbon electrodes (C–PSCs) possess the advantageous features of low cost, high stability and a simple fabrication process. They are considered a promising technology for producing cost-effective solar electricity. However, the power conversion efficiency of C–PSCs lags far behind that of the conventional gold-based counterparts due to the inefficient charge transfer and charge collection associated with the carbon electrodes and poor perovskite/carbon interfacial contact. A carbon electrode is generally deposited from a carbon paste (CP) composed of various carbon allotropes, additives, and solvents. The properties and compositions of the CPs directly influence the properties of the resultant carbon electrodes, their interfacial contact with layers underneath, and the device performance. In this review, we summarise the research on the development of CPs for carbon electrodes to achieve desirable properties, including electrical conductivity, processibility, chemical compatibility, and cost-effectiveness for the fabrication of C–PSCs. We also discuss the various structures of C–PSCs and the fabrication techniques for carbon electrodes. Finally, we present future perspectives on C–PSCs, focusing on the current challenges and possible solutions for making efficient, stable, and scalable C–PSCs. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Semiconducting lead (Pb) free organic-inorganic hybrid perovskites have become more attractive for possible applications in solar cells and other optoelectronic devices. In this study, a first-principles density functional theory (DFT) calculations have been carried out to explore the structural, electronic, optical and mechanical properties of Pb-free organic-inorganic hybrid perovskites MABX 3 (MA = CH 3 NH 3 , B = Sn, Ge; X = I, Br, Cl) and the results are compared with the Pb-containing perovskites MAPbX 3 (X = I, Br, Cl). High absorption, low reflectivity and high optical conductivity have been observed in our simulations. These compounds are found to be direct band gap semiconductors suitable for solar cells and other optoelectronic devices. Our calculation indicates that tin (Sn) has superior properties alternative to Pb as the Sn containing compounds have excellent electronic, optical and mechanical properties. MASnI 3 is found to be one of the best Pb-free materials embracing these properties. For example, the unique mechanical property of MASnI 3 makes the compound flexible and easy to be fabricated into thin films. We believe these results will benefit the development of Pb-free hybrid solar cells as well as other optoelectronic devices. Graphical abstract Image 1 Highlights • Physical properties of Pb-free MABX3 (B = Sn, Ge; X = I, Br, Cl) are studied. • MASnI 3 is found as the best Pb-free candidate for photovoltaics and optoelectronics. • Good optical properties of the material demonstrate its potential in optoelectronics. • Calculated elastic constants confirm the mechanical stability of the selected phase. • The material can be deposited in thin films due to its low bulk and shear moduli. [ABSTRACT FROM AUTHOR]

Organic-inorganic perovskite has shown one of the most rapid growths ever in photovoltaic history and achieved remarkable achievement with PCE of 22.1%. Since the first perovskite solar cells (PSCs) was reported in 2009, it always existed a problem that the performance of PSCs prepared in winter is much better than summer due to films cracking. In this article, we explored the reasons for this phenomenon and provided a corresponding solution. It was found that film cracking was a major contributor for losses of PSCs performance. By adjusting ambient temperature of operating environment, the film quality and device performance can be increased effectively. Result showed that mirror-like perovskite film surface without cracks can be prepared by control operating environment, and the power conversion efficiency was boosted from 13% to values more than 18% measured under standard solar conditions (AM 1.5G, 100 mW/cm 2 ). Furthermore, this method exhibits good reproducibility. It is expected that by this effective approach and better understanding of the perovskite preparation process, high efficiency and reproducible PSCs device can be prepared. [ABSTRACT FROM AUTHOR]

A unique bias-dependent phenomenon in CH 3 NH 3 PbI 3− x Cl x based planar perovskite solar cells has been demonstrated, in which the photovoltaic parameters derived from the current–voltage ( I–V ) curves are highly dependent on the initial positive bias of the I–V measurement. In FTO/CH 3 NH 3 PbI 3− x Cl x /Au devices, the open-circuit voltage and short-circuit current increased by ca . 337.5% and 281.9% respectively, by simply increasing the initial bias from 0.5 V to 2.5 V. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new strategy of using MASCN as an additive in the PbI 2 precursor for a sequential two-step film deposition method. • MASCN consumes PbI 2 for formation of perovskite intermediate phase to control the crystallization process for high-quality films with enlarged grain size and reduced GBs. • MASCN generates MA and HSCN gas to assist recrystallization of perovskite film for reduced bulk/surface defects. SCN- escapes from the films for maintaining the phase purity of perovskite films. • A promoted power conversion efficiency from 18.36% to 20.4% and enhanced device stability with a retention from 70% to 85% in the ambient air (relative humidity greater than 50%) for 1680 h are achieved. Thiocyanate (SCN-) has been reported to manage crystallization of perovskite films and improve their optoelectronic properties in solar cells. However, the mechanism of SCN- in preparation of high-quality (MAFA)Pb(IBr) 3 based light-absorbing layers has not been well investigated yet. In this work, we investigate the effects of SCN- on phase transition of (MAFA)Pb(IBr) 3 perovskite films and the corresponding device performance by introducing methylammonium thiocyanate (MASCN) in a PbI 2 precursor solution which is used to make perovskite by a two-step sequential deposition method. Characterization of the perovskite films has shown that a proper amount (1 mg/mL) of MASCN in PbI 2 can produce PbI 2 -MASCN seeds which act as a nucleation center for assisting heterogeneous nucleation of the (MAFA)Pb(IBr) 3. Meanwhile, MASCN helps to effectively control crystallization of the perovskite film by obtaining preferential crystal growth orientation. Furthermore, MASCN is beneficial to eliminate residual PbI 2 and prepare perovskite films with low trap-state density. Consequently, the power conversion efficiency (PCE) of the perovskite solar cells increases from 18.36% to 20.4%. An enhanced device stability against moisture is also observed in the MASCN-treated device which exhibits 90% retention of the initial efficiency after exposed to the ambient air for 1780 h. [ABSTRACT FROM AUTHOR]

The inclusion of long chain alkyl-amine organics in perovskite solar cells (PSCs) has been reported to enhance water-resistance of perovskite films, but this strategy lowers device efficiency at the same time. Herein, we develop an approach that combines molecular dimensionality control and interfacial passivation of perovskite layers using a novel post-device treatment (PDT) with the vapour of ethylene-amine salts of different carbon chain lengths to improve both efficiency and stability of the PSCs. The effect of a series of ligand vapours including ethylenediamine (EDA), diethylenetriamine (DETA) and triethylenetetramine (TETA) was systematically investigated. A thin hydrophobic two-dimensional (2D) perovskite capping layer formed in the device after the 3D perovskite was exposed to the vapour of long chain ethylene-amine molecules, such as DETA and TETA, which protected the underlying bulk 3D perovskite layer from moisture attack. An improved energy level alignment was obtained in the treated devices and that a reduced density of defects was present in the perovskite after treatment with DETA and TETA vapours. Consequently, enhanced efficiency from 17.07% to 18.09% (DETA) and improved moisture stability with PCE retention from 73.8% to 90.0% (TETA) under a relative humidity>65% for 1000 h were achieved by this vapour treatment respectively. Image 1 • Low dimensional perovskites form to protect the devices from moisture attack. • Interfacial modification with the ligand vapours reduces surface trap-state density. • Improved efficiency and prolonged stability have been achieved in treated devices. • Processing speed of the post treatment is associated with length of alkyl chains. [ABSTRACT FROM AUTHOR]