Dual Defect Passivation at the Buried Interface for Printable Mesoscopic Perovskite Solar Cells with Reduced Open-Circuit Voltage Loss

Numerous defects exist at the buried interface between the perovskite and adjacent electron transport layers in perovskite solar cells, resulting in severe non-radiative recombination and excessive open-circuit voltage (VOC) loss. Herein, a dual defect passivation strategy utilizing guanidine sulfate (GUA2SO4) as an interface modifier is first reported. On the one hand, the SO4 2- preferentially interacts with Pb-related defects, generating water-insoluble lead oxysalts complexes. Additionally, GUA+ diffuses into the perovskite and induces the formation of low-dimensional perovskite. These reactions effectively suppress trap states at the buried interface and perovskite boundaries in printable mesoscopic perovskite solar cells (p-MPSCs), thus increasing the carrier lifetime. Meanwhile, GUA2SO4 optimizes the interface energy band alignment, thus accelerating the charge extraction and transfer at the buried interface. This synergistic effect of trap passivation and interface energy band alignment modulation is strongly demonstrated by an increase in average VOC of 70 mV and the power conversion efficiency improvement from 17.51% to 18.70%. This work provides a novel approach to efficiently improve the performance of p-MPSCs through dual-targeted defect passivation at the buried interface.

Printable Counter Electrode with Metal Nitride as the Conductive Medium for Perovskite Solar Cells

Perovskite solar cells (PSCs) with a booming high power conversion efficiency (PCE) are on their road toward industrialization. A proper design of the counter electrode (CE) with low cost, high conductivity, chemical stability, and good interface contact with the other functional layer atop the perovskite layer is vital for the overall performance of PSCs. Herein, the application of titanium nitride (TiN) is reported as a conductive medium for the printable CE in hole-conductor-free mesoscopic PSCs. TiN improves the conductivity of the CE and reduces the resistivity from 20 to 10 mΩ∙cm. TiN also improves the wettability of the CE with perovskite and enhances the back interface contact, which promotes charge collection. On the other hand, TiN is chemically stable during processing and undergoes no distinguishable chemical reaction with halide perovskite. Devices with TiN as the conductive media in the CE deliver a champion PCE of 19.01%. This work supplies a considerable choice for the CE design of PSCs toward industrial applications.

Record-Efficiency Printable Hole-Conductor-Free Mesoscopic Perovskite Solar Cells Enabled by the Multifunctional Schiff Base Derivative

Tailoring multifunctional additives for performing interfacial modifications, improving crystallization, and passivating defects is instrumental for the fabrication of efficient and stable perovskite solar cells (PSCs). Here, a Schiff base derivative, (chloromethylene) dimethyliminium chloride (CDCl), is introduced as an additive to modify the interface between the mesoporous TiO2 electron transport layer and the MAPbI3 light absorber during the annealing process. CDCl chemically links to TiO2 and MAPbI3 through coordination and hydrogen bonding, respectively, and results in the construction of fast electron extraction channels. CDCl also optimizes the energy-level alignment of the TiO2/MAPbI3 heterojunction and improves the pore-filling and crystallization of MAPbI3 in the mesoscopic scaffold, which inhibits nonradiative recombination and eliminates open-circuit voltage losses. As a result, an impressive power conversion efficiency of 19.74%, which is the best one ever reported, is obtained for printable carbon-based hole-conductor-free PSCs based on MAPbI3.

Stratified Oxygen Vacancies Enhance the Performance of Mesoporous TiO2 Electron Transport Layer in Printable Perovskite Solar Cells

The low electrical conductivity and the high surface defect density of the TiO2 electron transport layer (ETL) limit the power conversion efficiency (PCE) of corresponding perovskite solar cells (PSCs). Here, the conductivity and defect modulation of the mesoporous TiO2 (mp-TiO2 ) ETL via oxygen vacancy (OV) management by the reduction and oxidation treatment are reported. Reduction treatment via reducing agent introduces abundant OVs into the TiO2 nanocrystalline particles on the surface and at the subsurface. The following oxidation treatment via hydrogen peroxide removes the surface OVs while remains the subsurface OVs, resulting in stratified OVs. The stratified OVs improve the conductivity of TiO2 ETL by increasing carrier donors and decrease nonradiative centers by reducing surface defects. Such synergy ensures the capability of mp-TiO2 as the well-performed ETL with improved energy level alignment, suppressed interface recombination, enhanced carrier extraction, and transport. As a result, printable hole-conductor-free carbon-based mesoscopic PSCs based on the modulated mp-TiO2 ETL demonstrate a highest reported PCE of 18.96%.

Depth-Dependent Post-Treatment for Reducing Voltage Loss in Printable Mesoscopic Perovskite Solar Cells

The printable mesoscopic perovskite solar cells consisting of a double layer of metal oxides covered by a porous carbon film have attracted attention due to their industrialization advantages. However, the tens-of-micrometer thickness of the triple scaffold leads to a challenge for perovskite to crystallize and for the charge carriers to separate and travel to the electrode, which limits the open circuit voltage (V_OC ) of such devices. In this work, a depth-dependent post-treatment strategy is demonstrated to synergistically passivate defects and tune interfacial energy band alignment. Two thiophene derivatives, namely 3-chlorothiophene (3-CT) and 3-thiophene ethylenediamine (3-TEA), are selected for the post-treatment. Energy-dispersive X-ray spectroscopy proves that 3-CT is uniformly distributed throughout the triple scaffold and effectively passivates the defects of the bulky perovskite, while 3-TEA reacts rapidly with the loose perovskite in the carbon layer to form 2D perovskite, forming a type II energy band alignment at the perovskite/carbon interface. As a result, the defect-assisted recombination is suppressed and the interfacial energy band is regulated, increasing the V_OC to 1012 mV. The PCE of the devices is enhanced from 16.26% to 18.49%. This depth-dependent post-treatment strategy takes advantage of the unique structure and provides a new insight for reducing the voltage loss.

Halide Perovskite Crystallization Processes and Methods in Nanocrystals, Single Crystals, and Thin Films

Halide perovskite semiconductors with extraordinary optoelectronic properties have been fascinatedly studied. Halide perovskite nanocrystals, single crystals, and thin films have been prepared for various fields, such as light emission, light detection, and light harvesting. High-performance devices rely on high crystal quality determined by the nucleation and crystal growth process. Here, the fundamental understanding of the crystallization process driven by supersaturation of the solution is discussed and the methods for halide perovskite crystals are summarized. Supersaturation determines the proportion and the average Gibbs free energy changes for surface and volume molecular units involved in the spontaneous aggregation, which could be stable in the solution and induce homogeneous nucleation only when the solution exceeds a required minimum critical concentration (C_min ). Crystal growth and heterogeneous nucleation are thermodynamically easier than homogeneous nucleation due to the existent surfaces. Nanocrystals are mainly prepared via the nucleation-dominated process by rapidly increasing the concentration over C_min , single crystals are mainly prepared via the growth-dominated process by keeping the concentration between solubility and C_min , while thin films are mainly prepared by compromising the nucleation and growth processes to ensure compactness and grain sizes. Typical strategies for preparing these three forms of halide perovskites are also reviewed.

Constructing Soft Perovskite-Substrate Interfaces for Dynamic Modulation of Perovskite Film in Inverted Solar Cells with Over 6200 Hours Photostability

High-performance perovskite solar cells (PSCs) depend heavily on the quality of perovskite films, which is closely related to the lattice distortion, perovskite crystallization, and interfacial defects when being spin-coated and annealed on the substrate surface. Here, a dynamic strategy to modulate the perovskite film formation by using a soft perovskite-substrate interface constructed by employing amphiphilic soft molecules (ASMs) with long alkyl chains and Lewis base groups is proposed. The hydrophobic alkyl chains of ASMs interacted with poly(triarylamine) (PTAA) greatly improve the wettability of PTAA to facilitate the nucleation and growth of perovskite crystals, while the Lewis base groups bound to perovskite lattices significantly passivate the defects in situ. More importantly, this soft perovskite-substrate interface with ASMs between PTAA and perovskite film can dynamically match the lattice distortion with reduced interfacial residual strain upon perovskite crystallization and thermal annealing owing to the soft self-adaptive long-chains, leading to high-quality perovskite films. Thus, the inverted PSCs show a power conversion efficiency approaching 20% with good reproducibility and negligible hysteresis. More impressively, the unencapsulated device exhibits state-of-the-art photostability, retaining 84% of its initial efficiency under continuous simulated 1-sun illumination for more than 6200 h at elevated temperature (≈65 °C).

Approaching the External Quantum Efficiency Limit in 2D Photovoltaic Devices

2D transition metal dichalcogenides (TMDs) are promising candidates for realizing ultrathin and high-performance photovoltaic devices. However, the external quantum efficiency (EQE) and power conversion efficiency (PCE) of most 2D photovoltaic devices face great challenges in exceeding 50% and 3%, respectively, due to the low efficiency of photocarrier separation and collection. Here, this study demonstrates photovoltaic devices with defect-free interface and recombination-free channel based on 2D WS₂ , showing high EQE of 92% approaching the theoretical limit and high PCE of 5.0%. The high performances are attributed to the van der Waals metal contact without interface defects and Fermi-level pinning, and the fully depleted channel without photocarrier recombination, leading to intrinsic photocarrier separation and collection with high efficiency. Furthermore, this study demonstrates that the strategy can be extended to other TMDs such as MoSe₂ and WSe₂ with EQE of 92% and 94%, respectively. This work proposes a universal strategy for building high-performance 2D photovoltaic devices. The nearly ideal EQE provides great potential for PCE approaching the Shockley-Queisser limit.

Modeling and Balancing the Solvent Evaporation of Thermal Annealing Process for Metal Halide Perovskites and Solar Cells

Triple-mesoscopic perovskite solar cells (PSCs) have attracted intensive attention due to the high stability, simple fabrication process, and low material cost. In this structure, the perovskite layer is hosted by a triple-mesoscopic scaffold of TiO₂ /ZrO₂ /carbon, and thus the crystal quality is sensitive to the thermal annealing process. Typically, the annealing process is conducted in a petri dish, for which the solvent evaporation of the perovskite precursor is slowed down, but not controllable and designable. To control the solvent evaporation, annealing chambers are first designed with different shape and vapor releasing channels. Then, physical simulations are performed by a finite element method, and it is found out that the chamber with a crowned top and releasing channels on the bottom sides can realize homogeneous distribution of the solvent vapor. To verify the simulation results, chambers are fabricated by 3D printing technique, for which the printing deviation can be as low as 100 µm. By balancing the solvent evaporation and release, the optimal solvent evaporation is achieved of the perovskite precursor in the triple-mesoscopic scaffold. This work offers a method to obtain homogeneous distribution of solvent vapor, and provides a new insight into understanding the influence of solvent evaporation during the thermal annealing process for PSCs.

Interfacial Energy Band Alignment Enables the Reduction of Potential Loss for Hole-Conductor-Free Printable Mesoscopic Perovskite Solar Cells

Perovskite solar cells (PSCs) have achieved high efficiencies with diversified device architectures. In particular, printable mesoscopic PSC has attracted intensive research attention due to its simple fabrication process and superior stability. However, in the absence of hole conductors, the unfavorable energy band alignment between the perovskite and the carbon electrode usually leads to the reduction of device performance, especially the open-circuit voltage (V_OC). Here, a p-type molecule, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), is utilized to post-treat the perovskite/carbon interface, which benefits the charge transfer and suppresses the charge recombination within the device. As a result, the post-treated device delivers a power conversion efficiency of 18.05% with an enhanced V_OC of 1044 mV. This work provides a facile method for tuning the interfacial energy band alignment and improving performance of printable mesoscopic PSCs.

Development of formamidinium lead iodide-based perovskite solar cells: efficiency and stability

Perovskite materials have been particularly eye-catching by virtue of their excellent properties such as high light absorption coefficient, long carrier lifetime, low exciton binding energy and ambipolar transmission (perovskites have the characteristics of transporting both electrons and holes). Limited by the wider band gap (1.55 eV), worse thermal stability and more defect states, the first widely used methylammonium lead iodide has been gradually replaced by formamidinium lead iodide (FAPbI3) with a narrower band gap of 1.48 eV and better thermal stability. However, FAPbI3 is stabilized as the yellow non-perovskite active phase at low temperatures, and the required black phase (α-FAPbI3) can only be obtained at high temperatures. In this perspective, we summarize the current efforts to stabilize α-FAPbI3, and propose that pure α-FAPbI3 is an ideal material for single-junction cells, and a triple-layer mesoporous architecture could help to stabilize pure α-FAPbI3. Furthermore, reducing the band gap and using tandem solar cells may ulteriorly approach the Shockley-Queisser limit efficiency. We also make a prospect that the enhancement of industrial applications as well as the lifetime of devices may help achieve commercialization of PSCs in the future.

Investigating the iodide and bromide ion exchange in metal halide perovskite single crystals and thin films

The anion exchange between MAPbX3 (X = I- or Br-) and MAX salts in a solution environment is investigated. We find that I- can enter MAPbBr3 single crystals (SC) in millimeter scale, while Br- can only penetrate the surface of MAPbI3 SC in a micrometer scale. Due to the lattice variation, the reaction is partially reversible.

Mesoporous-Carbon-Based Fully-Printable All-Inorganic Monoclinic CsPbBr3 Perovskite Solar Cells with Ultrastability under High Temperature and High Humidity

The all-inorganic CsPb(I_xBr_1-x)₃ (0 ≤ x ≤ 1) perovskite solar cells (PSCs) are attractive by virtue of their high environmental and thermal stability. Nevertheless, multiple-step deposition and high annealing temperature (>250 °C) and the structural and optoelectronic properties changes upon temperature-dependent phase-transition are potential impediments for highly efficient and stable PSCs. Herein, a space-confined method to fabricate stable lower-order symmetric pure monoclinic CsPbBr₃ phase at low temperature (<50 °C) is for the first time reported. It is found that the carbon-based mesoporous fully printable area can inhibit the phase transition to get a pure phase. Therefore, the device exhibits a power conversion efficiency of 7.52% with a low hysteresis index of 0.024. Moreover, the device passed the 1000 h 85 °C thermal test and the 200 cycles thermal cycling test according to IEC-61625 stability tests. These are critical progresses for achieving long-term stability and the stable pure inorganic perovskite phase of high-performance photovoltaics.

van der Waals Mixed Valence Tin Oxides for Perovskite Solar Cells as UV-Stable Electron Transport Materials

Stable electron transport materials (ETMs) with fewer surface defects and proper energy level alignments with halide perovskite active layers are required for efficient perovskite solar cells (PSCs) with long-term durability. Here, two-dimensional van der Waals mixed valence tin oxides Sn₂O₃ and Sn₃O₄ are controllably synthesized and applied as ETMs for planar PSCs. The synthesized Sn₂O₃ and Sn₃O₄ have size of 5-20 nm and disperse well in water as stable colloids for months. Both Sn₂O₃ and Sn₃O₄ exhibit typical n-type semiconductor energy band structures, low trap density, and suitable energy level alignments with halide perovskites. Steady-state power conversion efficiencies (PCEs) of 22.36% and 21.83% are obtained for Sn₂O₃-based and Sn₃O₄-based planar PSCs. In addition, the half cells without hole transport materials and back electrodes show good UV-stability with average PCE of 99.0% and 95.7% for Sn₂O₃-based and Sn₃O₄-based devices remaining after 1000 h of ultraviolet soaking with an intensity of 70 mW cm^-2.

Influence of precursor concentration on printable mesoscopic perovskite solar cells

Over the last decade, the power conversion efficiency of hybrid organic-inorganic perovskite solar cells (PSCs) has increased dramatically from 3.8% to 25.2%. This rapid progress has been possible due to the accurate control of the morphology and crystallinity of solution-processed perovskites, which are significantly affected by the concentration of the precursor used. This study explores the influence of precursor concentrations on the performance of printable hole-conductor-free mesoscopic PSCs via a simple one-step drop-coating method. The results reveal that lower concentrations lead to larger grains with inferior pore filling, while higher concentrations result in smaller grains with improved pore filling. Among concentrations ranging from 0.24-1.20 M¹⁾, devices based on a moderate strength of 0.70 M were confirmed to exhibit the best efficiency at 16.32%.

In situ transfer of CH3NH3PbI3 single crystals in mesoporous scaffolds for efficient perovskite solar cells

Printable mesoscopic perovskite solar cells are usually fabricated by drop-casting perovskite precursor solution on a screen-printed mesoporous TiO2/ZrO2/carbon triple-layer followed by thermal annealing. They have attracted much attention due to their simple fabrication process and remarkable stability. However, challenges lie in how to achieve complete pore fillings of perovskites in the meso-pores and to obtain high-quality perovskite crystals. Here, we report an in situ crystal transfer (ICT) process based on gas-solid interaction to deposit perovskite CH3NH3PbI3 absorber in the scaffold. CH3NH3PbI3 single crystals are first transformed into a liquid phase via exposure to methylamine gas flow. After complete infiltration into the nano-structured scaffolds, the liquid phase is converted back to the solid phase with reduction of methylamine gas partial pressure, maintaining the high-quality of CH3NH3PbI3 single crystals. Compared with the conventional drop-casting method, the ICT method effectively leads to interconnected morphology and prolongs the charge-carrier lifetime (from ∼37.52 ns to ∼110.85 ns) of the perovskite absorber in the scaffold. As a result, the devices can deliver a power conversion efficiency of 15.89%, which is attributed to the suppressed charge recombination and correspondingly enhanced open-circuit voltage of 0.98 V.

Amide Additives Induced a Fermi Level Shift To Improve the Performance of Hole-Conductor-Free, Printable Mesoscopic Perovskite Solar Cells

Solution-processable organic-inorganic perovskite solar cells have attracted much attention in the past few years. Energy level alignment is of great importance for improving the performance of perovskite solar cells because it strongly influences charge separation and recombination. In this report, we introduce three amide additives, namely, formamide, acetamide, and urea, into the MAPbI₃ perovskite by mixing them directly in perovskite precursor solutions. The Fermi level of MAPbI₃ shifts from -4.36 eV to -4.63, -4.65, and -4.61 eV, respectively, upon addition of these additives. The charge transfer between perovskite and mp-TiO₂ is found to be promoted as determined via TRPL spectra, and recombination in the perovskite is suppressed. As a result, the built-in electric field (V_bi) of the printable, hole-conductor-free mesoscopic perovskite solar cells based on these perovskites with amide additives is enhanced and a peak power conversion efficiency of 15.57% is obtained.

Two-Stage Melt Processing of Phase-Pure Selenium for Printable Triple-Mesoscopic Solar Cells

Hexagonal selenium with a direct band gap has been developed for optoelectronic applications for more than one century. The major advances in Se solar cells have been made using vacuum or solution-based processing methods. In this work, we demonstrate a new two-stage melt processing (TSMP) method for incorporating Se in printable triple mesoscopic solar cells in the ambient conditions. It is observed that polymerization and depolymerization between several types of selenium chains are simultaneously triggered during the melt processing, from which phase-pure hexagonal selenium is formed in the mesopores of solar cells with high crystallinity. The TSMP method has positive effects on the conduction-band energy level, band gap, and crystal phase of as-deposited Se, as revealed UV electron spectroscopy, UV-vis absorption spectroscopy, and in situ X-ray diffraction. The TSMP-based printable mesoscopic selenium solar cells show a power conversion efficiency of 2%, which is eight times that for devices based on the single-stage melting processing. These findings open up a new research direction of melting processing toward more efficient photovoltaic devices.

Modulation of Acceptor Position in Organic Sensitizers: The Optimization of Intramolecular and Interfacial Charge Transfer Processes

With respect to cyanoacryclic acid as the traditional acceptor and anchoring group in dye-sensitized solar cells, the introduction of stronger electron-deficient groups has greatly expanded the scope of molecular design and increased their efficiencies for organic dyes. In this contribution, benzothiadiazole (BTD) was selected as a representative acceptor to illustrate the influence of its position on the photophysical properties and corresponding photovoltaic performances. Through the insertion of BTD in different positions of the framework with the same composition units and orders, four sensitizers were designed and synthesized. The structure-property relationship demonstrated the preference of the suitable position of an electron acceptor for optimization of the spectra response and interfacial charge transfer. In our system, dye LI-96 with BTD in the middle of the conjugated bridge showed the broadest spectrum and achieved the best photovoltaic performance (8.25%), which may pave a new way to design or optimize the efficient sensitizers by rational design of the acceptor position.

In Situ Back-Contact Passivation Improves Photovoltage and Fill Factor in Perovskite Solar Cells

Organic-inorganic hybrid perovskite solar cells (PSCs) have seen a rapid rise in power conversion efficiencies in recent years; however, they still suffer from interfacial recombination and charge extraction losses at interfaces between the perovskite absorber and the charge-transport layers. Here, in situ back-contact passivation (BCP) that reduces interfacial and extraction losses between the perovskite absorber and the hole transport layer (HTL) is reported. A thin layer of nondoped semiconducting polymer at the perovskite/HTL interface is introduced and it is shown that the use of the semiconductor polymer permits-in contrast with previously studied insulator-based passivants-the use of a relatively thick passivating layer. It is shown that a flat-band alignment between the perovskite and polymer passivation layers achieves a high photovoltage and fill factor: the resultant BCP enables a photovoltage of 1.15 V and a fill factor of 83% in 1.53 eV bandgap PSCs, leading to an efficiency of 21.6% in planar solar cells.

The efficacy of tranexamic acid for orthognathic surgery: a meta-analysis of randomized controlled trials

The efficacy of tranexamic acid in orthognathic surgery remains controversial. We conducted a systematic review and meta-analysis to explore the influence of tranexamic acid on blood loss for orthognathic surgery. We performed a search of PubMed, Embase, Web of science, EBSCO, and Cochrane library databases through October 2017 for randomized controlled trials (RCTs) assessing the effects of tranexamic acid versus placebo on orthognathic surgery. Meta-analysis was performed using the random-effects model. Six RCTs were included in the meta-analysis. Overall, compared with placebo in orthognathic surgery, tranexamic acid administration results in significantly decreased blood loss [mean difference (MD)=-159.73; 95% confidence interval (CI)=-236.42 to -83.03; P<0.0001], and higher postoperative haemoglobin (MD=0.71; 95% CI=0.11 to 1.31; P=0.02), but has no remarkable impact on postoperative haematocrit (MD=1.23; 95% CI=-1.22 to 3.69; P=0.33) and operation time (MD=-2.35; 95% CI=-18.05 to 13.36; P=0.77). In addition, patients with orthognathic surgery need decreased amounts of irrigant fluid (MD=-229.23; 95% CI=-399.63 to -58.83; P=0.008) after using tranexamic acid. We concluded that tranexamic acid promotes the bleeding control in orthognathic surgery.

A low-temperature carbon electrode with good perovskite compatibility and high flexibility in carbon based perovskite solar cells

A low-temperature carbon electrode with good perovskite compatibility is employed in hole-transport-material free perovskite solar cells, and a champion power conversion efficiency (PCE) of 11.7% is obtained. The PCE is enhanced to 14.55% by an interface modification of PEDOT:PSS. The application of this carbon on ITO/PEN substrates is also demonstrated.

Spacer layer design for efficient fully printable mesoscopic perovskite solar cells

The spacer layer is a key component of fully printable mesoscopic perovskite solar cells, but its precise characteristics are far from being understood in relation to the device design. In the present work, we perform a detailed systematic study on the effects of spacer parameters, such as size of building blocks, layer thickness, etc., on properties of the perovskite filler, insulating ability and performance of fully printable mesoscopic perovskite solar cells by combining the techniques of time-resolved photoluminescence, high-resolution TEM, insulating resistance measurements, impedance spectroscopy and J–V characteristics. Drawing on the deep understanding from these studies, we formulate key principles, which are anticipated to guide the design of the advanced spacer layer for fully printable mesoscopic perovskite solar cells.

Key principles and reasonable routes are proposed to advance the spacer layer design for fully printable mesoscopic perovskite solar cells.

Challenges for commercializing perovskite solar cells

Perovskite solar cells (PSCs) have witnessed rapidly rising power conversion efficiencies, together with advances in stability and upscaling. Despite these advances, their limited stability and need to prove upscaling remain crucial hurdles on the path to commercialization. We summarize recent advances toward commercially viable PSCs and discuss challenges that remain. We expound the development of standardized protocols to distinguish intrinsic and extrinsic degradation factors in perovskites. We review accelerated aging tests in both cells and modules and discuss the prediction of lifetimes on the basis of degradation kinetics. Mature photovoltaic solutions, which have demonstrated excellent long-term stability in field applications, offer the perovskite community valuable insights into clearing the hurdles to commercialization.

Toward Industrial-Scale Production of Perovskite Solar Cells: Screen Printing, Slot-Die Coating, and Emerging Techniques

Perovskite solar cells (PSCs) have attracted intensive attention of the researchers and industry due to their high efficiency, low material cost, and simple solution-based fabrication process. Along with the development of device configurations, materials, and fabrication techniques, the efficiency has rapidly increased from the initial 3.8 to recent 22.7%. However, fundamental studies on PSCs are usually yielded through lab-scale procedures and carried out on small-area (≤1 cm²) devices. Recently, various deposition methods, such as screen printing, slot-die coating, soft-cover coating, spraying coating, etc., have been developed to enlarge the device area from the millimeters to hundreds of centimeters scale. Herein, we discuss the advances of up-scaling of PSCs and outline the fabrication methods from lab-scale to industrial-scale. Screen printing and slot-die coating have been regarded as the most promising methods toward the mass production of PSCs, and more emerging techniques are also anticipated in this enterprise.

A Multifunctional Bis-Adduct Fullerene for Efficient Printable Mesoscopic Perovskite Solar Cells

Printable mesoscopic perovskite solar cells (PMPSCs) have exhibited great attractive prospects in the energy conversion field due to their high stability and potential scalability. However, the thick perovskite film in the mesoporous layers challenges the charge transportation and increase grain boundary defects, limiting the performance of the PMPSCs. It is critical not only to improve the electric property of the perovskite film but also to passivate the charge traps to improve the device performance. Herein we synthesized a bis-adduct 2,5-(dimethyl ester) C₆₀ fulleropyrrolidine (bis-DMEC₆₀) via a rational molecular design and incorporated it into the PMPSCs. The enhanced chemical interactions between perovskite and bis-DMEC₆₀ improve the conductivity of the perovskite film as well as elevate the passivation effect of bis-DMEC₆₀ at the grain boundaries. As a result, the fill factor (FF) and power conversion efficiency (PCE) of the PMPSCs containing bis-DMEC₆₀ reached 0.71 and 15.21%, respectively, significantly superior to the analogous monoadduct derivative (DMEC₆₀)-containing and control devices. This work suggests that fullerene derivatives with multifunctional groups are promising for achieving high-performance PMPSCs.

Improved Performance of Printable Perovskite Solar Cells with Bifunctional Conjugated Organic Molecule

A bifunctional conjugated organic molecule 4-(aminomethyl) benzoic acid hydroiodide (AB) is designed and employed as an organic cation in organic-inorganic halide perovskite materials. Compared with the monofunctional cation benzylamine hydroiodide (BA) and the nonconjugated bifunctional organic molecule 5-ammonium valeric acid, devices based on AB-MAPbI₃ show a good stability and a superior power conversion efficiency of 15.6% with a short-circuit current of 23.4 mA cm^-2 , an open-circuit voltage of 0.94 V, and a fill factor of 0.71. The bifunctional conjugated cation not only benefits the growth of perovskite crystals in the mesoporous network, but also facilitates the charge transport. This investigation helps explore new approaches to rational design of novel organic cations for perovskite materials.

Fully printable hole-conductor-free mesoscopic perovskite solar cells based on mesoporous anatase single crystals

Mesoporous anatase single crystal titania with a small particle size was introduced into fully printable hole-conductor-free hybrid solar cells, which shows an optimal electron transport and carrier lifetime, leading to an enhanced device performance.

Boron-Doped Graphite for High Work Function Carbon Electrode in Printable Hole-Conductor-Free Mesoscopic Perovskite Solar Cells

Work function of carbon electrodes is critical in obtaining high open-circuit voltage as well as high device performance for carbon-based perovskite solar cells. Herein, we propose a novel strategy to upshift work function of carbon electrode by incorporating boron atom into graphite lattice and employ it in printable hole-conductor-free mesoscopic perovskite solar cells. The high-work-function boron-doped carbon electrode facilitates hole extraction from perovskite as verified by photoluminescence. Meanwhile, the carbon electrode is endowed with an improved conductivity because of a higher graphitization carbon of boron-doped graphite. These advantages of the boron-doped carbon electrode result in a low charge transfer resistance at carbon/perovskite interface and an extended carrier recombination lifetime. Together with the merit of both high work function and conductivity, the power conversion efficiency of hole-conductor-free mesoscopic perovskite solar cells is increased from 12.4% for the pristine graphite electrode-based cells to 13.6% for the boron-doped graphite electrode-based cells with an enhanced open-circuit voltage and fill factor.

Top-down approach from satellite to terrestrial rover application for environmental monitoring of landfills

This paper describes a methodology to perform chemical analyses in landfill areas by integrating multisource geomatic data. We used a top-down approach to identify Environmental Point of Interest (EPI) based on very high-resolution satellite data (Pleiades and WorldView 2) and on in situ thermal and photogrammetric surveys. Change detection techniques and geostatistical analysis supported the chemical survey, undertaken using an accumulation chamber and an RIIA, an unmanned ground vehicle developed by CNR IIA, equipped with a multiparameter sensor platform for environmental monitoring. Such an approach improves site characterization, identifying the key environmental points of interest where it is necessary to perform detailed chemical analyses.

Spacer improvement for efficient and fully printable mesoscopic perovskite solar cells

Highly dispersible TiO₂@ZrO₂ nanoparticles are synthesized to prepare an ultra-flat and crack-free spacer film, leading to an enhanced insulating ability compared to a conventional spacer.

Conjugated or Broken: The Introduction of Isolation Spacer ahead of the Anchoring Moiety and the Improved Device Performance

Acceptors in traditional dyes are generally designed closed to TiO₂ substrate to form a strong electronic coupling with each other (e.g., cyanoacrylic acid) to enhance the electron injection for the high performance of the corresponding solar cells. However, some newly developed dyes with chromophores or main acceptors isolated from anchoring groups also exhibit comparable or even higher performances. To investigate the relatively untouched electronic coupling effect in dye-sensitized solar cells, a relatively precise method is proposed in which the strength is adjusted gradually by changing isolation spacers between main acceptors and anchoring groups to partially control the electronic interaction. After an analysis of 3 different groups of 11 sensitizers, it is inferred that the electronic coupling should be kept at a suitable level to balance the electron injection and recombination. Based on a reference dye LI-81 possessing a cyanoacrylic acid as acceptor and anchoring group, both photocurrent and photovoltage are synergistically improved after the properties of isolation spacers were changed through the adjustment of the length, steric hindrance, and push-pull electronic characteristic. Accordingly, the rationally designed dye LI-87 with an isolation spacer of thiophene ethylene gives an efficiency of 8.54% and further improved to 9.07% in the presence of CDCA, showing a new way to develop efficient sensitizers.

Efficient Compact-Layer-Free, Hole-Conductor-Free, Fully Printable Mesoscopic Perovskite Solar Cell

A compact-layer-free, hole-conductor-free, fully printable mesoscopic perovskite solar cell presents a power conversion efficiency of over 13%, which is comparable to that of the device with a TiO₂ compact layer. The different wettability of the perovskite precursor solution on the surface of FTO and TiO₂ possesses a significant effect on realizing efficient mesoscopic perovskite solar cell. This result shows a promising future in printable solar cells by further simplifying the fabrication process and lowering the preparation costs.

A hole-conductor-free, fully printable mesoscopic perovskite solar cell with high stability

We fabricated a perovskite solar cell that uses a double layer of mesoporous TiO2 and ZrO2 as a scaffold infiltrated with perovskite and does not require a hole-conducting layer. The perovskite was produced by drop-casting a solution of PbI2, methylammonium (MA) iodide, and 5-ammoniumvaleric acid (5-AVA) iodide through a porous carbon film. The 5-AVA templating created mixed-cation perovskite (5-AVA)x(MA)1- xPbI3 crystals with lower defect concentration and better pore filling as well as more complete contact with the TiO2 scaffold, resulting in a longer exciton lifetime and a higher quantum yield for photoinduced charge separation as compared to MAPbI3. The cell achieved a certified power conversion efficiency of 12.8% and was stable for >1000 hours in ambient air under full sunlight.

Hole-Conductor-Free Mesoscopic TiO2/CH3NH3PbI3 Heterojunction Solar Cells Based on Anatase Nanosheets and Carbon Counter Electrodes

A hole-conductor-free fully printable mesoscopic TiO2/CH3NH3PbI3 heterojunction solar cell was developed with TiO2 nanosheets containing high levels of exposed (001) facets. The solar cell embodiment employed a double layer of mesoporous TiO2 and ZrO2 as a scaffold infiltrated by perovskite as a light harvester. No hole conductor or Au reflector was employed. Instead, the back contact was simply a printable carbon layer. The perovskite was infiltrated from solution through the porous carbon layer. The high reactivity of (001) facets in TiO2 nanosheets improved the interfacial properties between the perovskite and the electron collector. As a result, photoelectric conversion efficiency of up to 10.64% was obtained with the hole-conductor-free fully printable mesoscopic TiO2/CH3NH3PbI3 heterojunction solar cell. The advantages of fully printable technology and the use of low-cost carbon-materials-based counter electrode and hole-conductor-free structure provide this design a promising prospect to approach low-cost photovoltaic devices.

Two novel mutations of the NCSTN gene in Chinese familial acne inverse

BACKGROUND

Acne inversa (AI; MIM 142690), or hidradenitis suppurativa (HS), is a type of autosomal-dominant genodermatosis caused by mutations in γ-secretase. The complex of γ-secretase is a transmembrane protease that catalyses the cleavage of a set of membrane proteins and is comprised of four subunits encoded by four genes, including PSEN1, PSENEN, NCSTN and APH1. However, mutations associated with AI vary significantly, and it is important to define the specific mutation with a particular AI patient.

OBJECTIVE

To determine specific mutations in the γ-secretase gene associated with two Chinese AI families.

METHODS

Two families of three generations with apparent AI symptoms were examined through proband analysis. Genomic DNAs of the family members and a cohort of 100 healthy individuals were isolated and subjected to polymerase chain reaction (PCR) and direct DNA sequencing.

RESULTS

Two heterozygous missense mutations, c.647A>C (p.Q216P) in the exon 6, and c.223G>A (p.V75I) in the exon 3 of the NCSTN gene, were identified in the two families respectively. No mutations were found in 100 healthy individuals.

CONCLUSIONS

We have identified two novel mutations within the NCSTN gene associated with AI.