Perovskite Solar Cells

In article number 2101103, Yan-Zhen Zheng, Meilan Huang, Xia Tao, and co-workers fabricated NH₄Br-assisted rich guanidinium perovskite films that allow inducing the formation of the intermediate phase NH₄PbI₃ and alleviating the disorder of the octahedron caused by an alien cation. The resultant films behave extremely well in photovoltaic performance upon assembly as carbon-based perovskite solar cells.

Perovskite Solar Cells

In article number 2200023, Behzad Rezaei, Tayebeh Ameri, and co-workers applied the hydrophobic bifunctional graphene quantum dots, containing amide and alkyl chains, as an efficient interface modifier in perovskite solar cells to enhance the quality of perovskite films, passivate the defects at the surface and grain boundaries, and facilitate the hole extraction. As a result, perovskite solar cells exhibit an improved efficiency of 18.30% and keep over 80% of their initial efficiency after 960 h under ambient air.

Light Aging

In article number 2200132, Camilo A. Mesa, Sixto Giménez, Elena Mas-Marzá, and co-workers demonstrated through electrochemical and microstructural analysis that oxygen vacancies correlate with a migration of Bi towards the BiVO₄ surface. Light-aging has shown to increase the efficiency of BiVO₄ photoanodes due to oxygen vacancies modulation but establishing chemical changes has been challenging. Highly efficient photoelectrochemical oxidation reactions are key for solar-to-fuel synthesis.

Superhalogen is a promising candidate for defect passivation and stabilization of metal-halide perovskites due to its higher electronegativity and electron affinity than halides. This perspective gives an overview of studies regarding the use of superhalogen to develop efficient and stable perovskite solar cells and concludes with an outlook of further research directions.

This highlight aims to provide a snapshot of the recent exciting progress in carbon-electrode-based perovskite solar cells (PSCs), which brings a fresh and insightful perspective toward making perovskite photovoltaics affordable, fully printable, and durable.

This review shows the state-of-the art about the innovative strategies to stabilize perovskite nanocrystals in polar environments to improve the efficiency of photo(electro)catalytic solar-driven reactions.

Metal-halide perovskite single crystals are a viable alternative to the polycrystalline counterpart for efficient photovoltaic devices thanks to lower trap states, higher carrier mobility, and longer diffusion length. This review provides an extensive report about the growth methods, the devices architecture and design, and the strategies used to solve the open challenges of the devices’ stability.

The pure-phase FAPbI₃ perovskite material has not been prepared and the related properties are not deeply understood yet. This review summarizes the development and challenges of FA-based perovskite from component engineering to pure-phase perovskite technology and proposes a strategy for the development of pure-phase FAPbI₃ perovskite. This helps researchers to deeply understand the properties of FA-based perovskites.

The authors made a review of the advancement of organic ionic materials which are utilized for modification engineering in perovskite solar cells. These functional materials are divided into various sections according to their roles in terms of defect passivation on the perovskite surface and grain boundary, energy level alignment, modification of surface morphology, modulation of crystal structure, stabilization of perovskite phase, suppression of ion migration and improvement of stability. The corresponding working mechanisms are thoroughly discussed. Based on the deep understanding, an outlook is proposed at the end.

In situ electron microscopy, X-Ray-assisted and optoelectronic characterization techniques as the tools presenting the dynamic degradation changes of perovskite materials and devices’ microstructure, crystal structure, chemical composition, morphology, and photoelectric properties under different stress factors are effective to reveal the degradation mechanisms of perovskite solar cell and promote their commercial application.

Guanidinium (GA)-rich perovskite films are prepared via an NH₄Br-assisted two-step process in air conditions, in which NH₄Br is introduced to facilitate the transient phase (NH₄PbI₃) formation and reduce voids and pinholes in films. The fabricated carbon-based perovskite solar cells (C-PSCs) in ambient air deliver the highest efficiency of 16.19% and exhibit excellent stability against moisture, heat, and sunlight.

Hydrophobic graphene quantum dots (HGQDs) containing amide linkages, which consist of carbonyl and dodecyl amine groups, are successfully applied as an efficient bifunctional interface modifier to simultaneously boost the power conversion efficiency and stability of perovskite solar cells.

Prolonged light treatments over BiVO₄ photoanodes under air conditions induce Bi segregation in the surface, new intra-bandgap states, as well as the formation of oxygen vacancies.

An effective p-type doping strategy in Sb₂Se₃ is proposed and a higher hole carrier density of 10¹⁶ cm⁻³ is achieved for the first time, which shows the availability to optimize the performance of Sb₂Se₃-based solar cells. The defect physics that is decisive for the photovoltaic properties is revealed, providing guidance for further studies on doping in Sb₂Se₃.

A facile route is introduced to enhance the contact of NiO_X|perovskite by inserting a tetradecylamine (TeDA) interfacial layer, which modulates the wettability of NiO_X film and the transformation process of wet film to perovskite. Champion efficiency of 12.9% and improved stability are achieved for the larger area (53.64 cm²) perovskite solar modules based on spray-coated NiO_X.

A 3D opened hollow photothermal evaporator is designed using hierarchically porous CuS–cellulose composite as photothermal materials. This special structure not only imparts the solar evaporator with efficient water evaporation by minimizing energy loss, introducing cold evaporation surfaces for harvesting additional energy from surrounding environment, but also fully activates the evaporation on inner evaporation surfaces, thus delivering extremely high evaporation rates.

Herein, wavelength-dependent intensity-modulated photocurrent spectroscopy as a powerful tool to probe the charge carrier dynamics in complex systems is discussed. The technique is used to gain deep understanding of the loss mechanisms affecting promising materials for solar water splitting, such as WO₃/BiVO₄ heterojunction modified with CoFe Prussian blue catalyst, paving the way for future performance enhancement.

Photocurrents from nanostructured BiFeO₃ films produced using low-cost chemical solution deposition indicate a photoactive material. By developing a chemical solution deposition process for BiFeO₃, the production of high-quality multi-ferroic thin films for a range of applications is enabled, where a narrow bandgap photoactive material is needed. The process removes the need for an anneal in a controlled atmosphere.

The increase in butylammonium iodide (BAI) steric hindrance weakens its diffusion to grain boundary, resulting in excessive BAI residue on the surface of perovskite films. Because diffusion to grain boundary affects the passivation of grain boundaries and excessive BAI on the surface blocks hole transport, the photovoltaic performance of the device decreases gradually with the increase in BAI steric hindrance.

Inspired by the evaporation process of the tree in nature, the bionic solar evaporator consisting of a hydrogel solar absorber and bionic microchannels, achieves a fast water self-transport speed and a high solar water evaporation rate, which can be applied for wastewater treatment with a high purification rate up to 99.999% and a solar thermal efficiency as high as 92.1%.

The dynamics of light soaking (LS) effect, drift-diffusion simulations, and external voltage experiments reveal the correlation of the LS effect with ion migration in perovskite solar cells (PSCs). Furthermore, the introduction of Cs⁺ into perovskite films reduces the density of mobile ions in PSCs, which can not only suppress the LS effect notably but also enhance the long-term stability of PSCs.

A dimensionally graded 2D/3D heterostructure is formed by in situ growing 2D FPEA₂PbI₄ perovskite on top of the 3D wide-bandgap perovskite film, which leads to a high open-circuitvoltage of 1.31 V with a superior small open-circuit voltage loss of 0.43 V in a 1.74 eV perovskite solar cell system.

A dual-source electron beam coevaporation method is used for the controlled deposition of copper-doped nickel oxide and tungsten-doped niobium oxide as hole and electron transport layers, respectively. Perovskite solar cells based on these inorganic carrier-selective layers achieve power conversion efficiencies of 21.32% for a 0.155 cm² device and 19.01% for a 1 cm² device.

The ternary polymer solar cells demonstrate more balanced charge transport properties based on 20% third component, which improves blend film morphology and charge transport channels, where the ternary system with high average visible transmittance over 27% and power conversation efficiency over 12% is more suitable in ternary semitransparent devices than others.

A general strategy to prepare high-quality electron transport layers (ETLs) below 70 °C by ligand exchange on top of the inorganic CsPbI₂Br perovskite absorber layer is proposed. The ETLs possess smooth, dense, and pinhole-free morphologies, a suitable energy-level structure, favorable conductivity, and chemical stability, which give the whole photovoltaic devices high efficiencies and outstanding stabilities.

A study of the stability of ITO-based back contacts during CIGS synthesis is reported. For processing temperatures higher than 480 °C, an amorphous phase is formed at the surface of bare ITO, accompanied with degradation of transparency and device performance. Inclusion of a nanometric functional layer (and thickness optimization) allows to improve both parameters at high-temperature processing.

With demonstrated photocurrents approaching the theoretical limit, the photoelectrochemical (PEC) performance of BiVO₄ is limited by the relatively large bandgap. Mild heat treatment under a reactive hydrogen sulfide environment enables sulfur incorporation, which reduces the bandgap and redshifts the photoconductivity onset. The modified films are unfortunately unstable during PEC measurements, but this can be solved by introducing a NiO_x protection layer.

Herein, a hot-flow-assisted spin-coating method is proposed to prepare Cs_0.5FA_0.5PbI₃ films in the humid air environment. The presence of trace amount Cs₄PbI₆ not only passivates the defects but also improves the stability of Cs_0.5FA_0.5PbI₃. The carbon electrode–based perovskite solar cells (C-PSCs) with Cs_0.5FA_0.5PbI₃–Cs₄PbI₆ heterostructure film show an efficiency of 16.30%, which is the highest for methylamine-free low-temperature C-PSCs.

Addition of small organic molecules into the electron transport layer of inverted geometry organic solar cells is shown to seed crystallinity in the organic bulk heterojunction. Employing aromatic dicarboxylic acids on solution–gel-prepared zinc oxide electron transport layers, differing molecular morphologies of the active layer, with increased higher face-on orientations improving the power conversion efficiency, are demonstrated.

Herein, a way to realize 180 s of ultrafast texturing for mono-Si wafers is proposed by combining well-established metal-catalyzed chemical etching and a standard alkaline texturing process. Consequently, mono-Si passivated emitter rear contact solar cells with pyramid texture fabricated via the proposed texturing process are prepared to show an average η of 22.88% and a highest η of 23.02%.

The most stable vacancy-ordered halide double perovskite material based on Cs₂Pt(Cl,Br)_6, which remains intact in harsh pH conditions and shows panchromatic visible light absorption is reported. Through an anion-exchange process, core–shell heterostructures of Cs₂PtBr₆/Cs₂PtCl₆ with type-II band alignment are obtained. These structures were employed as photoanodes without any surface protection for solar water oxidation.

Through changing the Ni:V ratio, the band gap and band edge of nickel vanadates could be regulated, enabling Ni₂V₂O₇ and Ni₃V₂O₈ samples to photocatalytic CO₂ to CO in the presence of water under visible-light irradiation, while NiV₂O₆ sample showed almost no activity. Meanwhile, the higher concentration of oxygen vacancies over Ni₂V₂O₇ sample further enhanced the photocatalytic activity for CO₂ conversion into CO.

In this article, the use of water-based gold nanofluids is proved to enhance the photothermal conversion efficiency (PTE) of direct solar absorption collectors. Nanofluids (NFs) are colloidally stable and an increase in PTE of up to 121% with respect to water is achieved. Statistical analysis confirms the influence of nanoparticle (NP) size and concentration on the conversion efficiency.

An energy-level-aligning quaternary material system is reported with an ultra-wide bandgap and deep-highest occupied molecular orbital (HOMO) level polymer donor (PhI-Se) and an upshifted-HOMO nonfullerene acceptor (BTP) as the guests. The addition of PhI-Se and BTP greatly improves the toluene-processed active layer film quality and solar cell performance, yielding 17% efficiency. The host binary device only shows 13.1% efficiency when processed with toluene.

An ionic liquid butylammonium acetate (BAAc) is introduced to PbI₂ to tune the crystallization of perovskites to improve device stability. The BAAc-treated devices show better thermal stability with maintaining 79.5% of initial efficiency after 700 h of aging at 85 °C in nitrogen environment, as compared to the pristine device that retained 47.2% of its initial efficiency after 312 h.

Native In_x(O,S)_y buffer near Cu(In,Ga)(S,Se)₂ (CIGSSe) surface formed after air-annealing process gives rise to self-forming heterojunction, acting as charge separation and hole-blocking barrier with different valence band offset (ΔE_V) of native In_x(O,S)_y/CIGSSe to 1.4 eV. Herein, efficiency of 16.7% for flexible, Cd-free, and all-dry process CIGSSe solar cell on SUS substrate is ultimately attained with potential toward Lab-to-Fab transition.

Herein, an efficiency of 19.1% with near-zero hysteresis for a low-temperature planar n–i–p perovskite module (11 cm² aperture area, 91% aspect ratio) by avoiding dimethyl sulfoxide detrimental effect, by phenethylammonium iodide defect passivation and by optimized interconnections engineering is demonstrated. The scaling-up loss from cell to module is about 8%, showing homogeneous and defect-free layers, and high reproducibility.

This is a schematic diagram of the Zn buffer thin film formation process with different properties due to anion shape and pH. The interface between Cu(In,Ga)Se₂ (CIGS) and these Zn buffer thin films has different band structures, showing different performance of solar cells. These results are interpreted using the mechanism and transformation kinetics, and these interpretations are verified through analysis.

Oxidized poly(4-vinylpyridine) (O-P4VP) as an interfacial passivation layer of perovskite solar cells improves power conversion efficiencies to 21.11% and environmental stability. Based on metal–pyridine complexation, defect passivation of SnO₂ and increase in the grain size of perovskite are achieved simultaneously. The insoluble passivation layer in perovskite solutions also contributes to the fabrication of highly reproducible devices.

Both type II and Z-scheme charge transport mechanisms coexist in the novel Ni foam supported TiO₂@CdS thin-film photoelectrode, and an enhanced Z-scheme charge transfer effect accelerates the photogenerated charge separation and transport efficiency for photocatalytic (PC) and photoelectrochemical (PEC) hydrogen production.

Herein, the mechanism behind the short-circuit current loss observed upon introducing a 2D passivation layer in p–i–n perovskite solar cells is elucidated. Based on experiments and drift–diffusion simulations, the loss is linked to the inhomogeneity of the 2D passivation layer and the ionic space charge, which reduces the effective charge-carrier diffusion length.

The model system PTQ10:BOC-4F with high blend photoluminescence and negative offset is found to have a well-established equilibrium between singlet excitons, charge transfer states, and free charges. The discrepancy between high charge generation efficiency and low photoluminescence quenching is due to the shift of the equilibrium and slow hole transfer under short circuit and open circuit.

Energy harvesting by indoor photovoltaics is a very promising candidate to supply the energy for the demand of billions of internet-of-things devices. The indium-tin-oxide-free organic photovoltaic modules presented herein show great potential to fulfill these needs. Their large parallel resistance enables use cases at ultralow intensities of 50 lux, which is exceptional in this field.

Phenylethylammonium iodide (PEAI) treatment results in the formation of 2D PEA₂PbI₄ capping layer on 3D perovskite which passivates defects and increases hydrophobicity, but hinders electron collection. The ambient exposure downshifts energy levels facilitating charge collection, improving efficiency and stability. Energy-level alignment with PEAI treatment is also affected by hole transport layer (HTL)/perovskite interface modification, which facilitates favorable alignment with PEA₂PbI₄.

Featuring two hydroxyls and one carbonyl, 1,3-dihydroxypropan-2-one is introduced to passivate the uncoordinated lead cations and organic components on the surface of perovskite films via coordination and hydrogen bonding interactions. The device efficiency is improved from 20.21% to 23.26%, as well as better storage and thermal stability.

Ru-modified Bi₂MoO₆ has been successfully prepared using a one-step solvothermal method. As-prepared samples exhibit excellent photocatalytic activity in CO₂ reduction, with CO generation of 142.77 μmol⁻¹g⁻¹ and selectivity of 100% under simulated sunlight.

Herein, a poly(3-hexylthiophene) (P3HT)-based all-polymer solar cell (all-PSC) with a record efficiency of 7.35% is achieved by blending P3HT with a thermodynamically miscible polymer acceptor DCNBT-IDT. Morphology characterization and the Flory–Huggins model unravel that the formation of well-mixed morphology with fibrillary structures due to the appropriate miscibillity between P3HT and DCNBT-IDT is the key to the unprecedented efficiency.

A two-step orthogonal solvent method that enables straightforward fabrication of multilayer perovskite films is applied to construct the perovskite/carbon heterojunction for carbon-based perovskite solar cells (PSCs). Such a bulk heterojunction (BHJ) improves the interface contact and facilitates the hole transport between perovskite and the carbon electrode, significantly boosting the power conversion efficiency (PCE) to 16.4% with certification.

Guanidine thiocyanate (GASCN) is selected to regulate quality of PEA_0.1FA_0.9SnI₃-based perovskite film. The GASCN additive can form Lewis adducts with uncoordinated Sn atoms, inhibit the oxidation of Sn²⁺, and passivate the trap states. Thus, the unsealed tin-based perovskite solar cells with GASCN additive at the optimal process demonstrate a champion efficiency of 10.06% with better stability.

Cobalt modulation of SnO₂ electron transporting layer (ETL) significantly improves the performance and reduces the hysteresis of flexible perovskite solar cells (PSCs). Cobalt nitrate improves the crystallinity of SnO₂ nanoparticles, reduces surface defects of ETL and facilitates perovskite film growth, leads to hysteresis-less flexible PSCs with efficiencies over 20% in regular structure.

The strong interaction between 4-(bis(9,9-dimethyl-9 H-flouren-2-yl)amino)-1-naphthoic acid (KTN) and iodide vacancies exposing Pb²⁺ reduces the nonradiative recombination and elongates the carrier lifetime, leading to an outstanding PCE approaching 23% with a notable increase in open-circuit voltage (V_OC) of 60 mV.

Herein, a series-interconnected monolithic on-chip solar micromodules, with the capability to output high voltage by controlling the number of sub-cells, is proposed. An in-depth analysis of an unconventional non-shunt resistance type of leakage mechanism under injection are performed based on numerical simulation. Simulation reveals that high efficiency (≥24.0%) can be achieved by several unusual strategies to suppress leakage current.

The devices with 4-aminobutyric acid and 6-aminocaproic acid iodides forming 2D and 1D capping layers on the 3D films achieve high efficiencies of 23.48% and 23.11%, respectively, and show stable stability maintaining 93.73% and 91.58% of their initial efficiencies, respectively, after 2000 h exposure in atmosphere. 2D capping is more suitable for enhancing 3D perovskite performance than the 1D capping.

Owing to properties such as tailorable light absorption, solution processability, and low material toxicity, organic photovoltaic (OPV) devices are particularly suited to indoor light-harvesting applications. Such devices may be used incorporated into sensor devices for “Internet-of-Things” (IoT) applications. Herein, the implications for the fabrication of large-area devices and the requirements for large shunt resistances for low-light performance are examined.

Dopant free hole transporting materials i.e., derivatives of dibenzothiophene and carbazole used in perovskite solar cells reaching power conversion efficiency of 20.90% which correlate with effects of 1) the hole transport, 2) the efficiency of the hole transfer from the perovskite phase to hole transporters, and 3) the charge collection at an electrode.

With NMP solvent-induced lead halide-templated growth, large-area high-quality wide-bandgap perovskite films with suppressed photoinduced phase segregation are easily prepared without the use of antisolvent, achieving a champion power conversion efficiency of 19.46% with V_OC of 1.219 V, after further post-treatment of 2-ThMABr. These strategies show promise in the fabrication of large-scale perovskite solar modules and tandem devices.