Illumination In Air Research Articles

Tailoring Perovskite/C60 Interface by Reactive Passivators for Stable Tandem Solar Cells

AbstractIntegrating perovskite solar cells with crystalline silicon bottom cells in a monolithic two‐terminal tandem configuration enables power conversion efficiency (PCE) surpassing the theoretical limits of single‐junction cells. However, wide bandgap (WBG) perovskite films face challenges related to phase stability and open circuit voltage (VOC) deficit, particularly due to severe non‐radiative recombination at the perovskite/C60 interface. Here, the interfacial defects are passivated by incorporating a reactive passivator that reacts with lead halides to form low‐dimensional phases. The target product obtained by optimizing the reaction temperature not only suppresses recombination across the interface, but also facilitates the transfer of charge carriers. More importantly, this product can suppress phase segregation of WBG perovskite films under exposure to light illumination and moisture. This strategy enables a high VOC of 1.25 V for WBG perovskite device based on polymer hole transport layer and a certified stabilized PCE of 30.52% for a monolithic perovskite/silicon tandem solar cell. The unencapsulated tandem device retains 94% of its initial PCE over 200 h under continuous 1‐sun full spectrum illumination in air, demonstrating the improved phase stability.

Novel cathode buffer layer enabling over 21.6%/20.9% efficiency in wide bandgap/inorganic perovskite solar cells

Different types of hybrid organic/inorganic halide perovskite solar cells (PSCs) have attracted extensive research attention and showed extremely considerable practical application potential in current energy field, for instance, wide bandgap (WBG) PSCs are widely used in fabricating high-efficiency tandem devices, while inorganic perovskite solar cells (IPSCs) had been sought after by researchers due to its excellent thermal stability. However, either WBG PSCs or IPSCs were severely influenced by the carrier extraction and transport between the electron transfer layer and anode/cathode. On this basis, an in-situ oxygen plasma treated Ti doped ZnO film named TZO (O) was used as cathode buffer layer to regulate the energy-level alignment between the SnO2 layer and ITO electrode, optimize the crystal quality of perovskite and passivate perovskite defects through providing superior SnO2 film. It is found that the more suitable energy levels for the interlamination availably polished up carrier transport effect to a great extent, which could be seen in steady-state and time-resolved photoluminescence spectra, in addition to this, the perovskite film covered on TZO (O)/ SnO2 demonstrated larger perovskite crystals and less surface defects. As a consequence, the power conversion efficiency (PCE) of the optimized device with a bandgap of ≈ 1.66 eV up to 21.62%, and the efficiency of CsPbI2.85Br0.15 IPSCs is enhanced from 19.21% to 20.92%. Moreover, the unencapsulated TZO (O)-treated wide bandgap PSCs shows enhanced stability, retaining 89.47% of its initial efficiency after 1000 h in a N2 filled environment, while the unencapsulated IPSCs-based TZO (O) still remains 83.77% of its initial efficiency under continuous illumination in air for 325 h. This work exhibited that the buffer layer TZO (O) is a promising interfacial modification material for both n-i-p type wide bandgap PSCs and IPSCs.

Fabrication of graphene-rapped melamine sponge and its photothermal adsorption on viscous oil spill

Graphene oxide melamine sponges (GOMSs) were prepared by impregnating melamine sponge (MS) with graphene oxide (GO) dispersion. Thereafter, reduced graphene oxide melamine sponges (HGOMSs) were obtained by one-step heat treatment of GOMSs, and the effects of heat treatment and GO load on sponge structure, hydrophobicity/ lipophilicity, photothermal properties, mechanical properties and light-aided adsorption performances were evaluated. The results show that heat treatment under 400 °C is an optimum choice. A small amount of graphene could effectively wrap on the melamine sponge skeleton and closely combined with the sponge. This effectively wrapped structure can not only improve the photothermal and mechanical properties of the sponge, but also retain the rich pore structure of the sponge to provide sufficient space for oil adsorption. HGOMS prepared under 400 °C with 1 mg·ml−1 of GO concentration shows an average light absorption rate of 84.4% in the full solar spectral range. Under 1 sun illumination in air, the surface can quickly rise to 99.4 °C, and the bottom surface is 72.8 °C, showing excellent photothermal conversion performance. The saturated adsorption capacity on heavy oil reached 103.2 g·g−1 under 1 sun illumination. The material was reused through mechanical extrusion method. After 10 times of adsorption- extrusion operations, its saturated adsorption capacity still retained more than 80% of the first time. These characteristics make HGOMS an energy efficient and reusable adsorbent for oil spill.

Hexagonal Lead-Free Cs2AgBiI6 Perovskite Nanocrystals: A Promising Material for Solar Cell Application

Lead halide perovskite (LHP) nanocrystals (NCs) have extensive applications in optoelectronics. However, their high toxicity and low stability inhibit their commercialization. Herein, lead-free Cs2AgBiI6 NCs with a hexagonal phase are synthesized using a hot-injection process, which exhibit a band gap of 2.29 eV, a high absorption coefficient (∼2.8 × 105 cm–1), and a symmetric and narrow photoluminescence peak (full width at half-maximum = 10 nm). In addition, the hexagonal Cs2AgBiI6 NC films exhibit high resistance to heat, humidity, and illumination in air. Solar cells based on hexagonal Cs2AgBiI6 NCs are fabricated for the first time, achieving a power conversion efficiency (PCE) of 0.076%, which confirms its promising potential for photovoltaic applications.

Efficient Inverted Perovskite Solar Cells with a Low‐Dimensional Halide/Perovskite Heterostructure

AbstractThe photovoltaic performance of inverted (positive‐intrinsic‐negative) perovskite solar cells (PSCs) is predominantly limited by interfacial recombination loss. Here, by constructing a low‐dimensional halide/perovskite heterostructure, non‐radiative recombination pathways at the perovskite/C60 contact are effectively eliminated and a voltage loss of only 370 mV is achieved in inverted PSCs. Through molecular engineering of the organic spacer, a strong electronic coupling is enabled at the heterointerface, which effectively shifts the gap states out of the bandgap and leads to a prolonged carrier lifetime of 4.28 µs. Our strategy enables a power conversion efficiency of 24.09% (certified 23.54%) for inverted PSCs with an open‐circuit voltage of 1204 mV, and an efficiency of 21.89% (certified 21.48%) for centimeter‐scale cells. The devices retain 92% of the initial efficiency after 85 °C thermal aging for over 1400 h, and 95% of the initial efficiency after 1008 h of maximum power point operation under AM1.5G illumination in air.

Slot-die coating of a formamidinium-cesium mixed-cation perovskite for roll-to-roll fabrication of perovskite solar cells under ambient laboratory conditions

A deposition strategy is demonstrated for fabricating perovskite solar cells (PSCs) under ambient laboratory conditions. A nitrogen-flow treatment followed by a short (3 min), low-temperature (135 °C) anneal enables control of the nucleation and crystal growth of slot-die coated perovskite layers without the need for an anti-solvent for devices. PSCs using either glass or poly(ethylene terephthalate) (PET) substrates were prepared with an n-i-p device architecture and comprised a perovskite layer containing formamidinium and cesium cations, with or without the additive of 2-(2,3,4,5,6-pentafluorophenyl)-ethylammonium iodide (FEAI). The perovskite layer in glass-based devices was slot-die coated onto a stationary substrate with a moving coating head, whereas the deposition of the perovskite layer in PET-based devices was achieved by slot-die coating onto a moving (roll-to-roll, R2R) web using a stationary coating head. The processing conditions enabled the fabrication of PSCs displaying excellent temperature and humidity tolerance (up to 50% relative humidity). Devices fabricated on the glass substrates had power-conversion efficiencies (PCEs) of more than 18%, with PCEs of more than 15% measured for cells on the PET film substrates. The use of the FEAI additive improved the environmental stability of encapsulated glass-based PSC devices, which retained up to 70% of their initial PCE after 1000 h at maximum power point under 1-sun illumination in air. The scalability of the fabrication techniques used in this work, along with the low annealing temperature and ability to process in an ambient laboratory environment, makes this a promising approach for translation to industrial-scale R2R production processes.

Room temperature crystallization and stability of halide perovskite thin films

<p indent="0mm">The preparation of metal halide perovskite films with high crystallinity and high stability without heating in air is difficult to be realized, which is important for future large-scale applications of flexible perovskite solar cells. In this paper, we propose a method to realize the crystallization of perovskite thin films at room temperature, by using a mixed solution of three low-boiling polar molecules, 1,2-dimethoxyethane (DME), methylamine (MA), and ethanol (EA). The mixed solution effectively dissolves the perovskite precursor, and high crystallinity perovskite thin films can be prepared without annealing in air. The as-prepared perovskite film still maintains the lattice structure after 120 h of continuous illumination in air, showing high stability under water, oxygen, and illumination conditions. This method is suitable for the preparation of perovskite thin films with a band gap of <sc>1.60–1.78 eV.</sc> Finally, the flexible perovskite solar cells fabricated by this method achieved the highest photoelectric conversion efficiency of 19.63%. This provides a feasible direction for the large-scale commercial production of flexible perovskite solar cells.

Z-Scheme In2 S3 /NU-1000 Heterojunction for Boosting Photo-Oxidation of Sulfide into Sulfoxide under Ambient Conditions.

Photocatalytic oxidation of sulfide into sulfoxide has attracted extensive attention as an environmentally friendly strategy for chemical transformations or toxic chemicals degradation. Herein, we construct a series of In2 S3 /NU-1000 heterojunction photocatalysts, which can efficiently catalyze the oxidation of sulfides to form sulfoxides as the sole product under LED lamp (full-spectrum) illumination in air at room temperature. Especially, the sulfur mustard simulant, 2-chloroethyl ethyl sulfide (CEES), can also be photocatalytically oxidized with In2 S3 /NU-1000 to afford nontoxic 2-chloroethyl ethyl sulfoxide (CEESO) selectively and effectively. In contrast, individual NU-1000 and In2 S3 show very low catalytic activity on this reaction. The significantly improved photocatalytic activity is ascribed to the constructing of an efficient Z-scheme photocatalysts In2 S3 /NU-1000, which exhibits the enhancement of light harvesting, the promotion of photogenerated electron-hole separation, and the retention of high porosity of the parent MOF. Moreover, mechanism studies in photocatalytic oxidation reveal that the superoxide radical (. O2 - ) and singlet oxygen (1 O2 ) are the main oxidative species in the oxidation system. This work exploits the opportunities for the construction of porous Z-scheme photocatalysts based on the photoactive MOFs materials and inorganic semiconductors for promoting catalytic organic transformations. More importantly, it provides a route to the rational design of efficient photocatalysts for the detoxification of mustard gas.

Quantifying charge transportation for stable organic solar cells with a novel aluminum acetylacetone electron collection layer

Elucidating charge transportation mechanism for low-temperature solution-processed charge collection layer is crucial for efficient and stable organic solar cells (OSCs). Herein, we present a facile method to fabricate Al(acac)3 film and integrate it as electron collection layer (ECL) in OSCs. The PM6:Y6-based OSCs with Al(acac)3 ECL achieve a higher efficiency of 16.12% as compared to the control devices with a 10.90% efficiency. Importantly, the Al(acac)3-based devices present superior operational stability, which retains 60% of the initial PCE after 100 h continuous illumination in air. Investigations on optics and carrier recombination dynamics reveal that the improved performance benefits from high up to 98% transparency of Al(acac)3 ECL, optimized interfacial contact and enhanced exciton dissociation ratio from 85.10% to 97.51%. Further studies on quantified interface resistances during the internal charge transfer indirectly reflect the enhancement of stability. These results highlight the promising prospect of Al(acac)3 ECL in processing compatible, operationally stable high efficiency OSCs.

A data fusion approach to optimize compositional stability of halide perovskites

Summary Search for resource-efficient materials in vast compositional spaces is an outstanding challenge in creating environmentally stable perovskite semiconductors. We demonstrate a physics-constrained sequential learning framework to subsequently identify the most stable alloyed organic-inorganic perovskites. We fuse data from high-throughput degradation tests and first-principle calculations of phase thermodynamics into an end-to-end Bayesian optimization algorithm using probabilistic constraints. By sampling just 1.8% of the discretized CsxMAyFA1−x−yPbI3 (MA, methylammonium; FA, formamidinium) compositional space, perovskites centered at Cs0.17MA0.03FA0.80PbI3 show minimal optical change under increased temperature, moisture, and illumination with >17-fold stability improvement over MAPbI3. The thin films have 3-fold improved stability compared with state-of-the-art multi-halide Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3, translating into enhanced solar cell stability without compromising conversion efficiency. Synchrotron-based X-ray scattering validates the suppression of chemical decomposition and minority phase formation achieved using fewer elements and a maximum of 8% MA. We anticipate that this data fusion approach can be extended to guide materials discovery for a wide range of multinary systems.

Multifunctional brominated graphene oxide boosted charge extraction for high-efficiency and stable all-inorganic CsPbBr3 perovskite solar cells

The perovskite film with large grain size and high charge mobility is critical for the improvement of the power conversion efficiency (PCE) and the operational stability of perovskite solar cells (PSCs). Herein, multifunctional brominated graphene oxide (Br-GO) is prepared and innovatively used as an effective additive to incorporate into CsPbBr3 to form a large-grained high-quality perovskite film and to passivate defects at grain boundaries, which remarkably reduces the trap state density and carrier non-radiative recombination. Meanwhile, the hole mobility of the homogeneous CsPbBr3 + Br-GO photoactive layer is obviously increased due to the hole acceptor properties and high carrier mobility of Br-GO, resulting in an enhanced charge separation as well as transfer and suppressed carrier radiative recombination. Moreover, the Br-GO with a downshift valence band is employed as a hole-transporting material setting at perovskite/Carbon interface to further compensate energy levels and promote hole extraction. As a consequence, a champion PCE of 10.10% with an open-circuit voltage up to 1.602 V for the optimized PSCs with a configuration of FTO/c-TiO2/m-TiO2/CsPbBr3 + Br-GO/Br-GO/Carbon is obtained, which is much higher than 6.28% efficiency for the reference device. The unencapsulated solar cells also exhibit a remarkable tolerance toward 85% RH and long-term AM 1.5G illumination in air.

Annealing temperature mediated enhanced photosensitivity in bicone-like and flower-like structures of ZnO synthesized using Co-precipitation method

Abstract Samples of two ZnO structures - bicone-like as well as flower-like structures - have been synthesized by co-precipitation method using diethanolamine and diethanolamine with polyethylene glycol as starting materials. Further, the synthesized ZnO samples have been annealed at 400 °C, 600 °C and 800 °C separately. All synthesized samples as well as annealed samples have been characterized using UV–visible spectroscopy, photoluminescence (PL) spectroscopy, field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) technique, high-resolution transmission electron microscopy (HR-TEM), photoconductivity measurement technique and fourier transform infrared spectroscopy (FTIR). UV–visible spectra show absorption edges around 306–311 nm and 374–380 nm. PL spectra of prepared ZnO samples show a sharp and intense UV emission due to high concentration of zinc interstitial defects. XRD patterns confirm that all prepared ZnO samples possess hexagonal wurtzite structure. FE-SEM and HRTEM images show that the as-synthesized samples possess both bicone and flower-like structures, whereas annealed samples possess mostly flower-like structures. Photoconductivity property has been investigated under UV–vis illumination in air and vacuum. The samples annealed at 800 °C show highest photosensitivity as compared to as-synthesized samples and samples annealed at 400 °C and 600 °C. The photosensitivity gets increased with increase in annealing temperature as annealing results in increased concentration of zinc interstitial defects. In air medium, the annealed polymer-mediated ZnO samples show rise and decay curves with sharp rise and decay as compared to non-polymer-mediated ZnO counterparts. The photosensitivity of ZnO samples is improved in vacuum as compared to that in air, which may due to occurrence of carbo-optical reactions as a result of presence of hydrocarbons.

Ultra-black and self-cleaning all carbon nanotube hybrid films for efficient water desalination and purification

All-carbon nanotube (CNT) hybrid films are fabricated through a facile vacuum filtration method by using hydrophilic single-walled carbon nanotube (SWCNT) films as filters and multi-walled carbon nanotube (MWCNT) powder dispersed in ethanol as liquor. The hydrophilic SWCNT film provides penetration channels for water, while the superhydrophobic MWCNTs have self-cleaning, self-spreading, and broadband absorption ability. The hybrid film exhibits ultra-high solar absorbance (∼99%), low thermal conductivity, and excellent light-to-heat conversion capacity. The temperature of the hybrid film increases from 24 to 60 °C in 1 s under one-sun illumination in air. The individual hybrid film exhibits a high water evaporation rate of 1.37 kg m−2 h−1 and a solar thermal efficiency of 87.4% under one-sun after 1 h illumination. The solar thermal efficiency maintains at ∼80% when many pieces of hybrid films self-assemble into a large film (∼40 cm2). The hybrid films have great potential in the desalination of seawater and sewage treatment. Ion concentrations in seawater decrease significantly to drinkable water standards by only one distillation treatment. Organic pollutants, such as rhodamine B and methylene blue, are removed effectively from sewage water by using the hybrid films in a solar steam generator.

A perovskite solar cell owing very high stabilities and power conversion efficiencies

Owing to the superior optoelectronic properties of perovskite materials, the power conversion efficiency (PCE) of perovskite solar cells (PSCs) has been increased dramatically within several years, but the poor thermal, humidity, and light stability of these PSC devices hinders the progress to their practical application. We obtained an inspiration from two-dimensional (2D) Ruddlesden–Popper perovskite solar cells with good photovoltaic performance and placed the organic-inorganic hybrid perovskite layer inside two fully-inorganic CsPbI3 perovskite layers in the cubic α phase. The middle layer has lower stability than the two outer ones, which protect the middle layer by impeding the organic ions of the organic-inorganic hybrid perovskite middle layer from diffusing outside and causing damage to neighbor CTLs. Water molecules from air are also obstructed from reaching the hybrid perovskite layer. We used 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4) ionic liquid and 3-(decyldimethylammonio) propane-1-sulfonate (DDMAPS) and obtained phase-stable fully-inorganic α phase CsPbI3. The constructed PSCs have extremely high stabilities and high PCEs. After 1000 h of illumination under AM1.5 illumination in air at 60 °C (Humility: ~60%), PSCs with a sandwich structure of three perovskite layers maintain nearly all the original PCE of 21.32%, while those without that only remain 76.63%.

Crosslinkable metal chelate as the electron transport layer for efficient and stable inverted polymer solar cells

Efficient inverted polymer solar cells with crosslinked Hf(ACBV)4 as the ETL are demonstrated, exhibiting excellent operation stability under 20 hours continuous illumination in air.

Bifacial Passivation of Organic Hole Transport Interlayer for NiO x -Based p-i-n Perovskite Solar Cells.

Methoxy‐functionalized triphenylamine‐imidazole derivatives that can simultaneously work as hole transport materials (HTMs) and interface‐modifiers are designed for high‐performance and stable perovskite solar cells (PSCs). Satisfying the fundamental electrical and optical properties as HTMs of p‐i‐n planar PSCs, their energy levels can be further tuned by the number of methoxy units for better alignment with those of perovskite, leading to efficient hole extraction. Moreover, when they are introduced between perovskite photoabsorber and low‐temperature solution‐processed NiOx interlayer, widely featured as an inorganic HTM but known to be vulnerable to interfacial defect generation and poor contact formation with perovskite, nitrogen and oxygen atoms in those organic molecules are found to work as Lewis bases that can passivate undercoordinated ion‐induced defects in the perovskite and NiOx layers inducing carrier recombination, and the improved interfaces are also beneficial to enhance the crystallinity of perovskite. The formation of Lewis adducts is directly observed by IR, Raman, and X‐ray photoelectron spectroscopy, and improved charge extraction and reduced recombination kinetics are confirmed by time‐resolved photoluminescence and transient photovoltage experiments. Moreover, UV‐blocking ability of the organic HTMs, the ameliorated interfacial property, and the improved crystallinity of perovskite significantly enhance the stability of PSCs under constant UV illumination in air without encapsulation.

Molecular design enabled reduction of interface trap density affords highly efficient and stable perovskite solar cells with over 83% fill factor

Advancing perovskite solar cell (PVSC) technologies toward its theoretical power conversion efficiency (PCE) and optimum stability requires stringent control over interfacial trap densities in the devices. By introducing a new macromolecular interlayer material of PPDIN6 at the PCBM/Ag interface for planar p-i-n PVSCs, we succeeded in significantly reducing the trap density, thereby facilitating electron extraction and suppressing electron recombination at the interface. Consequently, a PCE of 20.43% was achieved with a record fill factor of 83.4%, which is one of the highest values for planar p-i-n PVSCs. Moreover, the amine groups in PPDIN6 could neutralize the migrating iodide ions and thus inhibit the formation of the insulating Ag–I bonds on the surface of the Ag electrode. As a result, we realized long-term stability for PPDIN6 based PVSCs, which maintained 85% of their initial performance after continuous operation at their maximum power point for 200 h under 1-sun illumination in air with a relative humidity of 30–50%.

Surface Engineering of Quantum Dots for Remarkably High Detectivity Photodetectors.

Ternary alloyed CdSe xTe1- x colloidal QDs trap-passivated by iodide-based ligands (TBAI) are developed as building blocks for UV-NIR photodetectors. Both the few surface traps and high loading of QDs are obtained by in situ ligand exchange with TBAI. The device is sensitive to a broad wavelength range covering the UV-NIR region (300-850 nm), showing an excellent photoresponsivity of 53 mA/W, a fast response time of ≪0.02s, and remarkably high detectivity values of 8 × 1013 Jones at 450 nm and 1 × 1013 Jones at 800 nm without an external bias voltage. Such performance is superior to what has been reported earlier for QD-based photodetectors. The photodetector exhibits excellent stability, keeping 98% of photoelectric responsivity after 2 months of illumination in air even without encapsulation. In addition, the semitransparent device is successfully fabricated using a Ag nanowires/polyimide transparent substrate. Such self-powered photodetectors with fast response speed and a stable, broad-band response are expected to function under a broad range of environmental conditions.

Ultraviolet light induced degradation of luminescence in CsPbBr3 perovskite nanocrystals

Perovskite nanocrystals (NCs) have been applied in light emitting diodes, but their stability is always the decisive factor to limit the practical application of devices. In this work, the influence of ultraviolet light illumination on the structural and luminescent properties of CsPbBr3 NC films with emissions of 495 and 520 nm was studied. It was demonstrated that the CsPbBr3 NC films exhibited significant degradation of photoluminescence (PL) under the illumination in air. The PbCO3 and PbO phases in CsPbBr3 NC films were observed after long illumination time with X-ray photoemission spectroscopy. The temperature-dependent PL spectra revealed that large amount of nonradiative traps were formed with increasing illumination time. The PL intensities, band energies, and bandwidths as well as PL lifetimes of the illuminated CsPbBr3 NC films were analyzed. The experimental results indicated that the PL degradation was attributed to the photo-oxidation of NCs under the illumination.

Compositional Engineering To Improve the Stability of Lead Halide Perovskites: A Comparative Study of Cationic and Anionic Dopants

The instability of perovskite solar cells is the single greatest barrier to their commercialization. While a number of studies have now looked at the effect of perovskite composition on device stability, many of these have examined only a single compositional variable. With many of these studies having been carried out under different environmental conditions, and still others lacking environmental controls entirely, it is often difficult to compare the relative effect of various cationic or anionic dopants. To address this knowledge gap, we fabricated CH3NH3PbI3-based solar cells where either the methylammonium or iodide ions were replaced with 20 mol % of a dopant ion (ethylammonium, formamidinium, bromide, or chloride). We then assessed their stability either in a controlled 85% relative humidity environment or under 1 sun illumination in air; both conditions have been previously shown to rapidly decompose CH3NH3PbI3. Of the dopants studied, the formamidinium cations imparted the best moisture resistan...