Improved Conversion Efficiency Research Articles

Enhanced N2 Activation on a Composite Co3Mo3N Nitride and La0.6Sr0.4Co0.2Fe0.8O3 Perovskite Cathode for High-Temperature Electrochemical Ammonia Synthesis

Electrochemical routes for ammonia synthesis could offer improved conversion efficiency, compatible integration with renewable energy sources, and a solution to distributed chemical production. In a conventional Haber–Bosch process, ammonia, NH3, is produced by reacting N2 and H2 at high temperatures and pressures. In an electrochemical pathway, the H2 production and pressurization steps can be bypassed by using N2 and H2O in an ambient-pressure solid-oxide electrolysis cell (SOEC). In this study, a SOEC with a composite cathode of A-site deficient lanthanum ferrite perovskite oxide and transition metal nitride Co3Mo3N was fabricated, and its activity for the nitrogen reduction reaction (NRR) was studied. The composite cathode produced ammonia at a rate of 4.0 × 10–11 mol s–1 cm–2 at 550 °C and 0.65 mA/cm2, which was an 8-fold enhancement compared to either of the pure phase electrodes. Relevant properties of Co3Mo3N, such as thermochemical stability, adsorption behavior, and mobility of nitrogen ions, were characterized by various techniques including in situ XRD, XAFS/XANES, NAP-XPS, temperature-programmed experiments, and in situ DRIFTS.

Efficient ternary organic solar cells enabled by asymmetric nonfullerene electron acceptor with suppressed nonradiative recombination

The open-circuit voltage (Voc) of organic solar cells (OSCs) is still far from the Shockley-Queisser limit due to the large non-radiative voltage loss (ΔVocnonrad). Reducing energy loss (Eloss) to obtain higher Voc without sacrificing Jsc and FF is the key to achieve further improvement in power conversion efficiency (PCE) of OSCs. In this work, we designed and synthesized a new asymmetric nonfullerene acceptor via a dual asymmetric strategy, named as SN-O. Under the synergistic effect of alkoxy chain and nitrogen atom substitution, the LUMO and HOMO energy levels of SN-O are significantly elevated compared to Y6, allowing SN-O to display a high open-circuit voltage with a reduced nonradiative energy loss (ΔEnonrad = 0.177 eV). The alkoxy side chain of SN-O brings an intramolecular conformational locking effect and the large dipole moment of asymmetric molecules facilitate the aggregation properties in thin films. The good miscibility allows Y6 and SN-O to form alloy acceptor attributing to the similar chemical structures. The addition of SN-O as the third component into the D18:Y6 system showed a significant reduction in the nonradiative energy loss and a favorable blend film morphology, thus improves exciton dissociation, charge transport and collection. Consequently, a high PCE of 18.3% was achieved for D18:Y6:SN-O ternary system with simultaneously enhancement of Voc, Jsc and FF, which is much higher than that of the binary devices.

Thermal management of photovoltaic-thermoelectric generator hybrid system using radiative cooling and heat pipe

Temperature regulation of photovoltaic modules is crucial for improving their efficiency. Nowadays, radiative cooling is a widely adopted passive thermal management technique for photovoltaic systems. Heat pipe and radiative cooling are two primary passive photovoltaic cooling methods employed in photovoltaic-thermoelectric generator hybrid systems. Therefore, this study proposes a novel photovoltaic-heat pipe-thermoelectric generator-radiative cooling hybrid system by applying heat pipe and radiative cooling simultaneously to control the temperature of the photovoltaic-thermoelectric generator hybrid system. A detailed computational model of the proposed system is developed and analyzed in the COMSOL Multiphysics. A comparative analysis of the photovoltaic module temperature drop and its efficiency enhancement between the proposed and the reference system consisting of only a photovoltaic module is performed. The effects of solar radiation, ambient temperature, and wind speed on both systems are studied under the Atacama Desert and Las Vegas climatic conditions. This proposed configuration reduced the photovoltaic temperature by efficiently evacuating its residual heat using a heat pipe and then rejecting it to the atmosphere using a radiative cooler. Results show that in contrast to the reference system, the proposed system reduced the average photovoltaic operating temperature by 2 °C for both the summer and winter seasons of the Atacama Desert and by 13 °C for Les Vegas. The maximum and minimum reductions of the photovoltaic temperature in the proposed system, as compared to the reference system, are 4 °C and 1.5 °C respectively, in June and 9 °C and 1 °C respectively, in January for the Atacama Desert. The maximum PV conversion efficiency and energy production improvements as compared to the reference system are 0.8% & 1.03% respectively, (for summer), and 0.3% & 0.94% respectively, (for winter) for the Atacama Desert, and 1.8% & 7.2% respectively, for the Las Vegas environment. The expected range of LCOE for a hybrid PV-HP-TEG-RC system is found to be between 0.065-0.089 USD/kWh. This study can help in improving the energy conversion efficiency by controlling the photovoltaic temperature using passive cooling methods in harsh environmental conditions such as the desert locations.

Electrolytic capacitor‐less reduced power processing single‐phase LED driver with power decoupling using split capacitor

SummaryLight emitting diode (LED) driver systems are now moving toward reduced processing power to improve conversion efficiency in indoor and outdoor applications. LED drivers connected to a single‐phase supply must meet the requirements for power factor correction with lower input current harmonics to maintain the alternating current (AC) power grid's quality and maintain a constant current through the LED load to eliminate the flickering effect in the light output. An LED driver is required to fulfill these requirements. In this paper, a new reduced processing power LED driver is proposed. By splitting the output capacitor into two capacitors and with the help of hardware design, the processing power can be reduced by using fewer semiconductors than in earlier designs. The proposed driver employs a simple ripple cancellation control approach to eliminate the 100 Hz ripple in the LED load current. Using this principle, an LED driver was designed and tested. The experimental results demonstrated that the proposed LED driver achieved an input power factor close to unity with lower input current harmonics and 92.5% of peak efficiency when operating at full power.

Multifunctional Small Molecule as Buried Interface Passivator for Efficient Planar Perovskite Solar Cells

AbstractThe improvement of power conversion efficiency (PCE) and stability of the perovskite solar cell (PSC) is hindered by carrier recombination originating from the defects at the buried interface of the PSC. It is crucial to suppress the nonradiative recombination and facilitate carrier transfer in PSC via interface engineering. Herein, P‐biguanylbenzoic acid hydrochloride (PBGH) is developed to modify the tin oxide (SnO2)/perovskite interface. The effects of PBGH on carrier transportation, perovskite growth, defect passivation, and PSC performance are systematically investigated. On the one hand, the PBGH can effectively passivate the trap states of Sn dangling bonds and O vacancies on the SnO2 surface via Lewis acid/base coordination, which is conducive to improving the conductivity of SnO2 film and accelerating the electron extraction. On the other hand, PBGH modification assists the formation of high‐quality perovskite film with low defect density due to its strong interaction with PbI2. Consequently, the PBGH‐modified PSC exhibits a champion power conversion efficiency (PCE) of 24.79%, which is one of the highest PCEs among all the FACsPbI3‐based PSCs reported to date. In addition, the stabilities of perovskite films and devices under high temperature/humidity and light illumination conditions are also systematically studied.

A Fast Transient Current-Mode Buck Converter With Linear Regulation Mode

This article proposes a configurable supply mechanism in the power stage to simultaneously improve the load transient response and power conversion efficiency. The power stage, comprising a dc–dc converter and an auxiliary power circuit (APC), can be organized depending on the variable load conditions. During step-load changes, the APC can provide an additional charging or discharging current to the output capacitance of the dc–dc converter to compensate for any differences between the load current and inductor current. Meanwhile, two auxiliary transient transistors are employed to immediately adjust the output level of the error amplifier because the peak current-mode control is used in the dc–dc converter. Thus, the recovery time and output transient ripple are enhanced significantly. At the steady state, the APC is inactivated; thus, the conversion efficiency of the dc–dc converter does not degenerate. Above medium loads, only the dc–dc converter is activated to deliver adequate power with high efficiency. At light loads, the APC acts as a linear regulator to take over the energy delivery scheme because power consumption is reduced effectively while the output voltage is kept. Therefore, the hybrid operation can guarantee improvements in load transient response and power conversion efficiency at light loads. The proposed converter was fabricated with 0.35- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m CMOS technology. The experimental results showed that the recovery times for 450-mA step-down and step-up loads are 1.6 and 2.0 μs, respectively. Comparing to when the transient mode is disabled, the recovery time of the output voltage is improved by over ten times when the transient mode is enabled. Further, the efficiency improvements with the proposed method at load current of 20 mA under the output voltages of 2.5 V and 1.8 V are 13.8% and 4.9%, respectively.

Fully Soft-Switched Ultra-High Step-Up Converter With Very Low Switch Voltage Stress

In this article, a fully soft-switched ultra-high-voltage gain converter with very low switch voltage stress is presented. To achieve ultra-high-voltage gain and very low switch voltage stress, two phases of a high step-up boost converter based on coupled inductors and switched capacitors are combined. In this converter, the main and auxiliary switches operate at zero-voltage switching (ZVS) and all diodes turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> at zero-current switching (ZCS). Thus, the reverse recovery problem of the diodes and the switching loss for all the semiconductor devices are mitigated. In addition, given that the voltage stress across the switches is remarkably low, <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfets</small> with low drain-source resistance (RDS-on) can be utilized to substantially lower the conduction loss. Hence, all the mentioned advantages have contributed to the converter efficiency improvement. Also, the existence of the common ground between the input and the output expands the converter applicability and reduces the control circuit complexity. Finally, a 300 W laboratory prototype is implemented to verify the theoretical analysis and a comprehensive comparison with counterpart structures is presented to illustrate the advantages and disadvantages of the presented converter.

Synergistic effects of plasma and catalyst in formaldehyde conversion over a Ni/α-Al2O3 catalyst in a dielectric barrier discharge reactor

Plasma-catalytic conversion of formaldehyde, as a representative volatile organic compound, in a dielectric barrier discharge reactor over a NiOx/α-Al2O3 catalyst was studied. Effects of plasma treatment on the physicochemical properties of the catalyst were studied and XPS analysis showed that plasma treatment increased the surface contribution of more active sites (i.e. Ni2+ and adsorbed O). However, the physical properties of the catalyst, including BET surface area and porosity, did not significantly change after plasma exposure. Presence of oxygen in the plasma-catalytic process improved conversion efficiency. Individual roles of plasma and catalyst in the selective conversion of formaldehyde to CO2, as the desired product, were decoupled. It was found that, in the oxygen-containing atmosphere, plasma can enhance formaldehyde conversion due to the facilitating role of O2-derived intermediates, such as ozone, while catalyst improves selectivity toward CO2 through catalyzing the complete oxidation path. Catalysts can make a substantial improvement in CO2 selectivity compared to the corresponding plasma-only conditions, even in an oxygen-free environment. Comparison between plasma-only, catalyst-only, and plasma-catalytic conditions with in-plasma catalyst (IPC) and post-plasma catalyst (PPC) configurations showed that CO2 yield decreased in the following order: IPC > PPC > catalyst-only > plasma-only. Superior performance under IPC conditions was due to: i) the improved catalyst properties upon plasma treatment; ii) facilitated CHO formation due to the impacts of both plasma and catalyst; iii) dominance of catalytic reaction steps after CHO formation resulting in the improved CO2 selectivity in the presence of a catalyst. The CO2 yield in the IPC system was greater than the summation of CO2 yield in the plasma-only and catalyst-only conditions, demonstrating the synergistic effects of plasma and catalyst. These results provide new insights into the facilitating role of oxygen in formaldehyde conversion, the beneficial role of catalyst in CO2 selectivity, and synergistic effects of plasma and catalyst in formaldehyde conversion over a NiOx/α-Al2O3 catalyst.

A Review of Miniaturized Advanced IC Rectenna for Energy Harvesting Applications

This article presents a review of different types of miniaturized rectenna integrated circuits IC used for energy harvesting applications such as medical applications. The rectenna design consists of two basic components: an embedded antenna that collects radio-frequency RF energy from the surrounding environment, and the rectifier circuit that converts AC-RF energy values into DC voltage for usage in low-power electronics devices such as implantable medical devices (IMDs). Microwave Schottky diodes HSMS-285x and SMS-763x series are used as a voltage doubler rectifier with an implanted antenna to improve conversion efficiency and the output voltage at a given input power and appropriate load. There are many challenges in the implantable rectenna IC design such as biocompatibility, miniaturization, patient safety, compact size, resonant frequency, bandwidth, radiation efficiency, and insensitivity to detuning. This review article summarizes the overall rectenna research carried out for new different design strategies in implant medical applications that operated at industrial scientific, and medical (ISM) bands such as 2.45GHz and 5.8GHz.

Ethylenediamine Vapors‐Assisted Surface Passivation of Perovskite Films for Efficient Inverted Solar Cells

Defects present at the surface or within the bulk of halide perovskites act as a barrier to charge transfer/transport, induce nonradiative recombination thereby limit open‐circuit voltage (VOC), and accelerate degradation in the perovskite solar cells (PSCs). Passivation of these defects at surfaces, interfaces, and grain boundaries to suppress the charge recombination is therefore imperative to improving photovoltaic performance in the PSCs. Herein, a facile posttreatment of perovskite surface by ethylenediamine (EDA) via mixed solvent vapor annealing method is reported. The results show that only a trace amount of EDA causes significant suppression of nonradiative recombination leading to over 100 mV increased VOC and ≈22% improvement in power conversion efficiency (PCE) of the inverted PSCs. The key reasons for this improvement are an upward shift in the Fermi energy level, reduced lattice strain and Urbach energy, and reduction in nonradiative recombination upon EDA passivation. These lead to a PCE exceeding 20% up from 16% for a nonpassivated film. The unencapsulated EDA‐modified PSCs also demonstrate an improved shelf‐life and retain 87% of the initial PCE after 850 h.

3D Polydentate Complexing Agents for Passivating Defects and Modulating Crystallinity for High‐Performance Perovskite Solar Cells

AbstractThe grain boundaries (GBs)/surface defects within perovskite film directly impede the further improvement of photoelectric conversion efficiency (PCE) and stability of planar perovskite solar cells (PSCs). Herein, 3D phytic acid (PA) and phytic acid dipotassium (PAD) with polydentate are explored to synchronously passivate the defects of perovskite absorber directly in multiple spatial directions. The strong electron‐donating groups (H2PO4) in the PA molecule afford six anchor sites to bind firmly with uncoordinated Pb2+ at the GBs/surface and modulate perovskite crystallization, thus enhancing the quality of perovskite film. Particularly, PAD containing an additional (K→PO) push–pull structure promotes the dominant coordination of phosphate group (PO) with Pb2+ and passivates halide anion defects due to the complexation of potassium ions (K+) with iodide ions (I‐). Consequently, the PAD‐complexed PSCs deliver a champion PCE of 23.18%, which is remarkably higher than that of the control device (19.94%). Meanwhile, PAD‐complexed PSCs exhibit superior moisture and thermal stability, remaining 79% of their initial PCE after 1000 h under continuous illumination, while the control device remain only 48% of their PCE after 1000 h. This work provides important insights into designing multifunctional 3D passivators for the purpose of simultaneously enhancing the efficiency and stability of devices.

Numerical assessment and optimization of highly efficient lead-free hybrid double perovskite solar cell

In this work, a performance assessment of a double perovskite Cs2BiCuI6 solar cell with the typical lead-based perovskite CH3NH3PbI3 as an active layer is presented using SCAPS-1D software. The theoretical analysis depicts the improvement in power conversion efficiency (PCE) for Cs2BiCuI6-based solar cells. This shows that in the coming future, the hybrid double perovskite Cs2BiCuI6 possess the capability to replace toxic CH3NH3PbI3-based solar cell which would help to create lead-free harmless solar cells. Detailed structural parameters optimization such as the absorbing layer thickness, and charge carrier mobility, and variation in interface defect density is carried out to enhance the device efficiency. This gives a PCE of 24.84 % for a hybrid double perovskite-based solar cell. The optimized values are 1013 cm−3, and 5 cm2 V−1 s−1 for interface defect density and carrier mobility respectively which also enhances the fill factor to 82 % with open circuit voltage of 1.28 V and 24.54 mA/cm2 short circuit current density Jsc.

An approach to low-temperature oscillation and high efficiency of thermoacoustic prime mover: influence of end face and reduction area of phase adjuster

The Phase Adjuster (PA) has contributed to the reduction of the onset temperature and improvement of the energy conversion efficiency of thermoacoustic systems. In this study, we investigated the performance characteristics of thin medal-shaped PAs representing the PA end faces. The results show that inserting 2 mm thick medal-shaped PAs lowered the onset temperature by 220 K. However, the insertion of thicker medal-shaped PAs maintained the onset temperature. In contrast, the energy conversion efficiency increased with the medal-shaped PA thickness. The energy conversion efficiency for 2 mm thick PAs was lower than that without PA. In addition, the thinner the medal-shaped PAs, the lower the power required for oscillation but the lower the energy conversion efficiency. These effects of the medal-shaped PA thickness indicate the necessity of different design guidelines for designing PAs for low-temperature oscillation and high efficiency in thermoacoustic systems.

Facile fabrication of ZnCo2S4@MWCNT as Pt-free counter electrode for high performance dye-sensitized solar cells

Substitution of platinum as a counter electrode material in dye-sensitized solar cells (DSSCs) is critical because Pt is rare and expensive. In addition, Pt-based counter electrodes have problems with the long-term stability of DSSCs. Among Pt-free electrocatalysts, composite materials are of great interest because they can be advantageous due to the combined performance of their components. Here, we present a ternary ZnCo2S4 composite grown on multi-walled carbon nanotubes as a Pt-free counter electrode for the reduction of triiodide in DSSCs. The composite ZnCo2S4@MWCNT was synthesized in a simple two-step process: (i) spray coating of a MWCNT dispersion on a FTO glass substrate, followed by (ii) solvothermal growth of the ternary sulfide ZnCo2S4 on a MWCNT layer. Cyclic voltammetry analyzes showed superior electrocatalytic activity of the composite in the reduction of triiodide compared to Pt. Electrochemical impedance spectroscopy measurements of symmetric dummy cells showed lower charge transfer resistance of ZnCo2S4@MWCNT (RCT = 5.54 Ω × cm2) than the traditional Pt electrocatalyst (7.07 Ω × cm2) in catalyzing the triiodide-to-iodide conversion reaction. The photovoltaic measurements of dye-sensitized solar cells showed an improved conversion efficiency of ZnCo2S4@MWCNT (8.55%) with excellent stability compared to Pt (8.19%).

Effect of Different Ligands Coating on the Photovoltaic Performance of CdSe Quantum Dot-Sensitized Solar Cells

In this article, oleic acid (OA), oleylamine and tri-n-octylphosphine (OAm-TOP), and OA-TOP were used as ligands in the synthesis of CdSe quantum dots (QDs), respectively. Effect of three different ligands on the photovoltaic performance of CdSe QD-sensitized solar cells (QDSCs) is systematically investigated. Based on the results of UV-vis absorption spectra, it is confirmed that the absorption range is widen for CdSe QDs coated with OAm-TOP or OA-TOP compared with OA. Electrochemical impedance spectroscopy (EIS) study indicates that CdSe QDs synthesized using OAm-TOP or OA-TOP can better passivate the surface defects of QDs resulting in the improvement of photoelectric conversion efficiency (PCE) of devices. The optimized PCE of 3.6% was achieved for CdSe QDSCs modified with OAm-TOP.

Gigahertz optoacoustic vibration in Sub-5 nm tip-supported nano-optomechanical metasurface

The gigahertz acoustic vibration of nano-optomechanical systems plays an indispensable role in all-optical manipulation of light, quantum control of mechanical modes, on-chip data processing, and optomechanical sensing. However, the high optical, thermal, and mechanical energy losses severely limit the development of nano-optomechanical metasurfaces. Here, we demonstrated a high-quality 5 GHz optoacoustic vibration and ultrafast optomechanical all-optical manipulation in a sub-5 nm tip-supported nano-optomechanical metasurface (TSNOMS). The physical rationale is that the design of the semi-suspended metasurface supported by nanotips of <5 nm enhances the optical energy input into the metasurface and closes the mechanical and thermal output loss channels, result in dramatically improvement of the optomechanical conversion efficiency and oscillation quality of the metasurface. The design strategy of a multichannel-loss-mitigating semi-suspended metasurface can be generalized to performance improvements of on-chip processed nano-optomechanical systems. Applications include all-optical operation of nanomechanical systems, reconfigurable nanophotonic devices, optomechanical sensing, and nonlinear and self-adaptive photonic functionalities.

Multiple Function Synchronous Optimization by PbS Quantum Dots for Highly Stable Planar Perovskite Solar Cells with Efficiency Exceeding 23%

AbstractColloidal lead sulfide (PbS) quantum dots (QDs), which possess quantum confinement effect and processing compatibility with perovskite, are regarded as an excellent material for optimizing perovskite solar cells (PSCs). However, the existing PSCs optimized by PbS QDs are still facing the challenges of poor performance of the charge transport layers, low utilization in the near‐infrared (NIR) region, and unsuitable energy level alignment, which limit the improvement of power conversion efficiency (PCE). Herein, a synchronous optimization strategy is realized via simultaneously introducing PbS QDs into SnO2 electron transport layer and employing rare‐earth‐doped PbS QDs (Eu:PbS QDs) film with hydrophobic chain ligands as the NIR light‐absorping layer and hole transport layer (HTL) of devices. PbS QDs effectively decrease the density of trap states by passivating defects. Eu:PbS QDs film with adjustable bandgap is employed as an absorption layer to broaden the NIR spectral absorption. The well‐matched energy level between Eu:PbS QDs layer and perovskite layer implies efficient hole transfer at the interface. The successful synchronous optimization greatly elevates all photovoltaic parameters, reaching a maximum PCE of 23.27%. This PCE is the highest for PSCs utilizing PbS QDs material in recent years. The optimized PSCs retain long‐term moisture and light stability.

Understanding Silicon Heterojunction Solar Cells with nc‐SiC/SiO2as an Alternate Transparent Passivating Front Contact and Computational Design Optimization

The potential performance of silicon heterojunction solar cells applying transparent passivating contact (TPC) at the front side, based on a nc‐SiC:H/SiO2layer stack, is modeled and investigated. Herein, a complete multiscale electro‐optical device model of TPC solar cells is developed. The model is then used to understand and analyze such cells and search for potential conversion efficiency improvement paths. The influences of contact layer thicknesses and other properties on device performance are studied. An algorithm‐based optimization of cell electro‐optical performance is performed. It is implemented by coupling a genetic algorithm with a finite element method‐based TPC solar cell device model. Optimum front contact layer thicknesses are calculated. For optically optimized TPC contact layer thicknesses, an optical improvement of around 0.5 mA cm−2is found. Moreover, for complete electro‐optical optimization of TPC layers, about 0.27% absolute value increment in power conversion efficiency is calculated. At the rear side, proper designing of optimizing carrier transport using active dopant concentration of p‐type a‐Si:H layer and indium tin oxide layer has shown a potential to reach power conversion efficiency beyond 25%.

Indium-based transparent conductive oxides developed for perovskite and perovskite-silicon tandem solar cell applications

Silicon solar cells are a mature PV technology; however, they are approaching their fundamental efficiency limit. Further efficiency improvements require a technological change towards silicon-based tandem solar cells, where a second absorber material with a higher band gap is stacked on top of silicon to reduce thermalization losses. For this purpose, perovskite-based solar cells have gained growing interest due to their rapid improvements in power conversion efficiencies, and promises of lower levelized costs of electricity. However, for perovskite-silicon tandem solar cells to surpass the current industry standard of silicon solar cells, efficiencies higher than 30 %, and long-term device stability are required.This paper focuses on the goal of improving the overall device efficiency of perovskite-silicon tandem solar cells by optimization of the top transparent conductive oxide (TCO) electrode. Sputtering processes for the TCOs indium tin oxide (ITO) (standard DC sputtering with ceramic target) and indium zinc oxide (IZO) (reactive serial co-sputtering process - magnetron) were developed and investigated. TCO films were optimized with regard to their optical properties, quantified here as the absorption weighted with solar spectral data, as well as to their electrical characteristics assessed with 4-pt resistivity and Hall-effect measurements to quantify resistivity, carrier concentration, and mobility. The best performing TCOs were then integrated as front electrode in perovskite and perovskite-silicon tandem solar cells to evaluate their impact on the device level. The optimized IZO film resulted in up to 1 mA/cm2 improvement of short circuit current density of the tandem solar cells.

Synergistic Effects of Interfacial Energy Level Regulation and Stress Relaxation via a Buried Interface for Highly Efficient Perovskite Solar Cells

An electron-transport layer with appropriate energy alignment and enhanced charge transfer is critical for perovskite solar cells (PSCs). In addition, interface stress and lattice distortion are inevitable during the crystallization process of perovskite. Herein, IT-4F is introduced into PSCs at the buried SnO2 and perovskite interface, which assists in releasing the residual stress in the perovskite layer. Meanwhile, the work function of SnO2/IT-4F is lower than that of SnO2, which facilitates charge transfer from perovskite to ETL and consequently leads to a significant improvement in the power conversion efficiency (PCE) to 23.73%. The VOC obtained is as high as 1.17 V, corresponding to a low voltage deficit of 0.38 V for a 1.55 eV bandgap. Consequently, the device based on IT-4F maintains 94% of the initial PCE over 2700 h when stored in N2 and retains 87% of the initial PCE after operation for 1000 h.