Improved Power Conversion Efficiency Research Articles

Stabilized Perovskite Quantum Dot Solids via Nonpolar Solvent Dispersible Covalent Ligands.

The ligand exchange procedure of CsPbI3 perovskite quantum dots (PQDs) enables the fabrication of thick and conductive PQD solids that act as a photovoltaic absorber for solution-processed thin-film solar cells. However, the ligand-exchanged CsPbI3 PQD solids suffer from deterioration in photovoltaic performance and ambient stability due to the surface traps, such as uncoordinated Pb2+ sites on the PQD surface, which are generated after the conventional ligand exchange process using ionic short-chain ligands dissolved in polar solvents. Herein, a facile surface stabilization is demonstrated that can simultaneously improve the photovoltaic performance and ambient stability of CsPbI3 PQD photovoltaic absorber using covalent short-chain triphenylphosphine oxide (TPPO) ligands dissolved in a nonpolar solvent. It is found that the TPPO ligand can be covalently bound to uncoordinated Pb2+ sites and the nonpolar solvent octane can completely preserve the PQD surface components. Owing to their synergetic effects, the CsPbI3 PQD photovoltaic absorber stabilized using the TPPO ligand solution dissolved in octane exhibit higher optoelectrical properties and ambient stability than the control absorber. Consequently, CsPbI3 PQD solar cells composed of PQD photovoltaic absorbers fabricated via surface stabilization strategy provide an improved power conversion efficiency of 15.4% and an enhanced device stability.

Contact Engineering and In Situ Formation of 2D Perovskite Via Solid‐Phase Growth for Efficient Hole‐Transport‐Layer‐Free Perovskite Solar Cells

Perovskite Solar Cells In article number 2300020, Congcong Wu, Haijin Li, and co-workers present a contiguous contact of perovskite/carbon interface achieved by in situ formation of 2D perovskite through a solid phase reaction when fabricating a carbon electrode. The 2D perovskite interlayer not only passivates surface defects but also enables a seamless contact at the perovskite/carbon interface and promotes carrier transport, thereby improving power conversion efficiency and stability of hole-transport-layer-free perovskite solar cells simultaneously.

Syntheses of efficient nickel oxide film by low-temperature fabrication technique for high-performance perovskite solar cells

Interface modification is an effective technique to improve power conversion efficiency (PCE) of perovskite solar cells (PSCs). In this study, three kinds of hole transport layers (HTLs), including planar-nickel oxide (P-NiOx) film, surface-nanostructured-NiOx (S-NiOx) film, and modified-NiOx (M-NiOx) film, are synthesized by low-temperature fabrication technique. Furthermore, M-NiOx film is defined by modifying P-NiOx film with ultra-low concentration NiOx nanoparticles. The results show that the M-NiOx film has higher conductivity and carrier transport ability than those of P-NiOx and S-NiOx. The special morphology of M-NiOx film is beneficial to improving the crystallinity of MAPbI3 perovskite film. Thus, the PSC based on M-NiOx film exhibits the highest short-circuit current density (Jsc) of 21.30 mA cm−2, which is larger than those of PSCs based on P-NiOx (17.74 mA cm−2) and S-NiOx films (16.56 mA cm−2). The optimized PSC based on M-NiOx film exhibits the high photovoltaic performance with PCE of 16.67%. The optimized PSC with M-NiOx film shows a long-term stability. After storing in a nitrogen-filled glove box for 1000 h, the PSC with M-NiOx film still has 85% of its initial PCE.

Perovskite interface defect passivation with poly(ethylene oxide) for improving power conversion efficiency of the inverted solar cells.

Inverted perovskite solar cells (PSCs) attract researchers' attention for their potential application due to the low-temperature fabrication, negligible hysteresis and compatibility with multi-junction cells. However, the low-temperature fabricated perovskite films containing excessive undesired defects are not benefit for improving the performance of the inverted PSCs. In this work, we used a simple and effective passivation strategy that Poly(ethylene oxide) (PEO) polymer as an antisolvent additive to modify the perovskite films. The experiments and simulations have shown that the PEO polymer can effectively passivate the interface defects of the perovskite films. The defect passivation by PEO polymers suppressed non-radiative recombination, resulting in an increase in power conversion efficiency (PCE) of the inverted devices from 16.07% to 19.35%. In addition, the PCE of unencapsulated PSCs after PEO treatment maintains 97% of its original stored in a nitrogen atmosphere for 1000 h.

Interface Engineering Enhances the Photovoltaic Performance of Wide Bandgap FAPbBr3 Perovskite for Application in Low‐Light Environments

AbstractUnderwater solar cells (UWSCs) provide an ideal alternative to the energy supply for long‐endurance autonomous underwater vehicles. However, different from conventional solar cells situated on land or above water, UWSCs give preference to use wide bandgap semiconductors (≥1.8 eV) as light absorber to match underwater solar spectra. Among wide bandgap semiconductors, FAPbBr3 perovskite is under prime consideration owing to its matching optical bandgap (≈2.3 eV), outstanding photoelectric properties, easier processability, etc. Unfortunately, for FAPbBr3 solar cells, substantial interface defects greatly limit the charge carrier extraction efficiency, thus limiting the device performance, especially in underwater low‐light environments. This study employs a molecular self‐assembly strategy to effectively eliminate the interfacial defects. As a result, a great improvement in power conversion efficiency (PCE) from 6.44% to 7.49% is obtained, which is among the best efficiency reported for inverted FAPbBr3 solar cells up to date. Besides, a champion PCE of 30% is obtained under 520 nm monochromatic light irradiation (4.8 mW cm−2). These results demonstrate that FAPbBr3 solar cells present a tremendously promising application in UWSCs.

Improved Power Conversion Efficiency and Stability of Perovskite Solar Cells Induced by Molecular Interaction with Poly(ionic liquid) Additives.

Ionic liquid (IL) additives proved to have a positive effect on the device efficiency and stability of perovskite solar cells. However, since ILs are small molecules and undergo Coulomb interactions, they can easily aggregate and evaporate over long times, which would cause instabilities during a long-term device operation. To overcome these problems, we polymerize ILs into macromolecules and incorporate them into perovskite films as well as into the corresponding solar cells. Both cations and anions of the used poly[1-(2-acryloylethyl)-3-methylimidazolium] bis (trifluoromethane) sulfonamides (PAEMI-TFSIs) are designed to coordinate with the Pb and I of PbI62- octahedra, respectively, which changes the crystallization behavior of the perovskite films. Importantly, the PAEMI-TFSI efficiently passivates electronic defects on the grain boundaries and thereby enhances the charge-carrier transport in the perovskite film. As a result, PAEMI-TFSI-modified MAPbI3 solar cells show a high power conversion efficiency of 22.4% and an excellent storage stability (92% of the initial efficiency remains after 1200 h operation in a nitrogen atmosphere for nonencapsulated devices).

Boosting the Performance of Perovskite Solar Cells through Systematic Investigation of the Annealing Effect of E-Beam Evaporated TiO2.

Electron transport layer (ETL) plays an undeniable role in improving the performance of n-i-p planar perovskite solar cells (PSCs). Titanium dioxide (TiO2) is known as a promising ETL material for perovskite solar cell. In this work, the effect of annealing temperature on optical, electrical, and surface morphology of the electron-beam (EB)-evaporated TiO2 ETL, and consequently on the performance of perovskite solar cell, was investigated. It was found that annealing treatment at an optimized temperature of 480 °C considerably improved the surface smoothness, density of grain boundaries, and carrier mobility of TiO2 film, which resulted in nearly 10-fold improvement in power conversion efficiency (11.16%) in comparison with the unannealed device (1.08%). The improvement in performance of the optimized PSC is attributed to the acceleration of charge carrier extraction, as well as suppression of the recombination at the ETL/Perovskite interface.

The impact of carbon emissions trading policy on carbon emission of China's power industry: mechanism and spatial spillover effect.

Carbon emission trading policy (CETP) is an important tool for energy savings and emission reduction. However, the effect of CETP on carbon emission reduction in power industry is still unknown. This paper uses the difference-in-differences (DID) model and the intermediary effect model to test the impact and mechanism of CETP on power industry carbon emissions. In addition, a spatial difference-in-differences (SDID) model is established to analyze the spatial spillover effect. The results show that CETP has a significant inhibitory effect on power industry carbon emissions and the results are still valid after endogenous and robust tests. The improvement of technology level and power conversion efficiency plays an intermediary role for CETP to reduce power industry carbon emissions. The optimization of power generation structure is likely to become another important way for CETP to play its role in the future. The spatial spillover effect test shows that CETP not only has a significant inhibitory effect on power industry carbon emissions in the pilot areas but also has a negative spatial spillover effect on power industry carbon emissions in the surrounding non-pilot areas. The heterogeneity tests show that CETP has the most significant reduction effect in the central region of China and the strongest spatial spillover inhibiting effect in the eastern region. The purpose of this study is to provide decision-making references for government to achieve China's dual-carbon goal.

A simple-structured benzo[1,2-b:4,5-b’]dithiophene-based molecule as a third component enables organic solar cells with over 18.2% efficiency

Research has shown that ternary strategy is an effective tool for improving the performance of organic solar cells (OSCs) and simple-structured small molecules with low-cost and wide bandgap which broadens the scope of the choice in third components recently attracted the attention of researchers. Herein, a small molecule with benzo[1,2-b:4,5-b’]dithiophene (BDT) core named BR-C12 which mixed well with PM6 has been designed and synthesized. Incorporating BR-C12 as third component into PM6:Y6, BR-C12 exhibits a complementary absorption with PM6 and Y6, promoted exciton dissociation and charge collection, reduced bimolecular recombination, resulting in more ordered molecular packing. The PM6:Y6:BR-C12 (1:1.2:0.1, weight ratio) OSC shows an improved power conversion efficiency (PCE) of 17.02% in comparison to host binary devises (16.42%). In addition, by employing BR-C12 as third component into PM6:L8-BO, the ternary device based on PM6:L8-BO:BR-C12 also achieves significant enhancement in device photovoltaic performance with a PCE of 18.26%. In addition, BR-C12-added ternary devices exhibit improved stability than binary ones. This work presents a method for constructing high-performance ternary OSCs and enriches the abundance of materials for the third components.

Multifunctional interface passivation by benzothiophene amine for stable perovskite solar cells with suppressed charge recombination

Interfacial passivation is the focal point for the preparation of efficient and stable perovskite solar cells. A holistic modification strategy employing multifunctional interfacial material of [1]benzothieno[3,2-b][1]benzothiophene-2-amine (BTBT-NH2) between tin oxide and perovskite is presented in this paper. It can be chemically linked to tin oxide by Lewis base coordination to reduce the oxygen vacancy in tin oxide. Furthermore, BTBT-NH2 containing lone pair electrons can passivate unliganded lead ions in perovskite and anchor lead iodide completely at the bottom of perovskite through N-H bond, forming more nucleation sites and improving the film-forming quality and crystallinity of PbI2 and perovskite. Further analysis reveals that the modification of BTBT-NH2 can reduce trap density, thus suppressing charge recombination and improving power conversion efficiency (PCE). Surprisingly, after being stored at 22 °C and 30% relative humidity in ambient conditions for nearly 1000 h, the unpackaged device maintains 90% of its initial PCE. The results show that BTBT-NH2 interfacial modification is an effective strategy for obtaining stable and efficient perovskite solar cells.

Multifunctional Cross‐Linked Polyurethane Polymer as Interface Layer for Efficient and Stable Perovskite Solar Cells

AbstractIn the past decade, perovskite solar cells (PSCs) have made remarkable progress in improving power conversion efficiency (PCE). In order to further improve the photovoltaic performance and long‐term stability of PSCs, the interface layer is essential. A multifunctional cross‐linked polyurethane (CLPU) is designed and synthesized via the spontaneous quaternization of polyurethane and 1, 6‐diiodohexane on the surface of the perovskite layer. CLPU layer cannot only effectively induce secondary crystallization and passivate the surface defects of perovskite, reduce the non‐radiative recombination, but also effectively block the moisture invasion. By this strategy, Cs0.05FA0.95PbI3 PSCs with excellent reproducibility, is realized, achieving a PCE of 23.14% with an open‐circuit voltage of 1.11 V, a short‐circuit current density of 25.69 mA cm−2, and a fill factor of 0.81. In addition, the unencapsulated devices show enhanced stability in 35 ± 5% relative humidity (RH) near 3000 h and in 65 ± 5% RH over 700 h. This study provides valuable insights into the role of CLPU interface layer in PSCs, which are essential for the design of high‐performance devices.

A novel of WS2–MoCuO3 supported with graphene quantum dot as counter electrode for dye-sensitized solar cells application

A novel tungsten disulfide-molybdenum copper oxide composite supported with graphene quantum dots (WM@GQDs) has been synthesized as a counter electrode (CE) for dye-sensitized solar cells (DSSCs) using a simple and low-cost ultrasonication method. The unique structure of WM@GQDs exhibits excellent power conversion efficiency due to its high catalytic activity and charge transport properties. In addition, the graphene quantum dots (GQDs) provide more active sites in the zero-dimensional materials for an I/I3− redox reaction which can improve the electrical and optical properties of the composite. The results indicate that the amount of GQDs in the composite affect the effectiveness of solar devices. When 0.9%wt of GQDs was used, the WM@GQDs composite achieved an efficiency of 10.38%, which is higher than that of the expensive platinum CE under the same conditions. The mechanism behind the improved power conversion efficiency (PCE) of the composite sample is also discussed in detail. Therefore, WM@GQDs can be an efficient material to replace platinum in DSSCs as a CE.

Nanoscale Surface Analysis Reveals Origins of Enhanced Interface Passivation in RbF Post Deposition Treated CIGSe Solar Cells

AbstractAlkali post deposition treatments (PDTs) of Cu(In,Ga)Se2 absorbers have boosted the power conversion efficiency (PCE) of the solar cell devices in the last years. A detailed model explaining how the PDTs impact the optoelectronic properties at the nanoscale is still lacking. Here, via various scanning probe techniques, X‐Ray photo‐electron spectroscopy and high resolution secondary ion mass spectroscopy it is shown that the RbF PDT treatments lead to a one to one exchange of Rb with Cu at the surface. This exchange takes place in the naturally occurring Cu‐depleted CIGSe surface, known as the ordered vacancy compound. A detailed comparison between samples with different PDTs after various cleaning procedures furthermore highlights the necessity to perform all the measurements on NH4OH cleaning surfaces only. After NH4OH, no RbInSe2 phase could be detected at the surface anymore and the surface bandgap, as measured with scanning tunneling spectroscopy is only 1.7 eV. The findings demonstrate that the existence of a RbInSe2 phase is most likely not responsible for the recent improvements in power conversion efficiency for state of the art solar cells. The primary effect of the PDT treatment is a modification of the ordered vacancy compound, where Cu is exchanged with Rb.

Latest Updates of Single-Junction Organic Solar Cells up to 20% Efficiency

Single-junction organic solar cells have reached a power conversion efficiency of 20% with narrow bandgap non-fullerene electron acceptor materials such as Y6, as well as with large band gap electron donor materials and their derivatives. The power conversion efficiency improvement of single-junction organic solar cells is a result of highly efficient light harvesting in the near-infrared light range and reduced energy losses with the most promising active layer layout currently available, Bulk-Heterojunction. Ternary blending is known to be the most advanced strategy to construct Bulk-Heterojunction structures in organic solar cells at present. In this review, we examine different devices based on Bulk-Heterojunction structures with efficient electron donors and acceptors. Then, we review the performance of binary and ternary organic solar cells with high power conversion efficiency, in conjunction with different anode and cathode interfaces used in recent studies of high-power conversion efficiency. Finally, we present perspectives on the future development of single-junction organic solar cells.

18% efficiency of ternary organic solar cells enabled by integrating a fused perylene diimide guest acceptor

Constructing ternary organic solar cells (OSCs) has been the widely used and effective strategy to further enhance photovoltaic performance. Here, a novel perylene diimide (PDI) derivative, FPDI-2PDI, was developed by attaching two PDI chromophores to the bay-position of fused PDI dimer. The wide bandgap FPDI-2PDI was used as a guest electron acceptor in the classic PM6:Y6 system. The top-performing ternary device achieved simultaneously increased open-circuit voltage (Voc) of 0.848 V, short-circuit current density (Jsc) of 27.47 mA cm-2 and fill factor (FF) of 77.20%, yielding a significantly improved power conversion efficiency (PCE) of 18.00%, which is much higher than PCE of 16.63% of the control PM6:Y6 binary device. The incorporation of FPDI-2PDI is conducive to improving solar energy utilization, suppressing charge recombination, facilitating exciton dissociation and charge collection while enhancing the blend morphology, thus leading to increased photovoltaic performance in the corresponding ternary device. This work indicates that proper molecular design will make the PDI derivatives to be very competitive guest acceptors to construct high-efficiency ternary OSCs.

A 200 MHz Passive Rectifier With Active-Static Hybrid VTH Compensation Obtaining 8% PCE Improvement

This work presents a passive rectifier system operating at 200MHz for implantable medical devices. In the CMOS passive rectifier, the gates of NMOS and PMOS are biased separately by using RC networks. In the rectifier, the bias resistor is divided into several pieces and implemented over individual deep N-well (DNW). In this way, the AC losses on the resistors can be reduced. To further improve the power conversion efficiency (PCE) of the rectifier, the static V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> compensation is applied on PMOS switches based on active V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> compensation on NMOS switches. Since the current spikes brought by the digital circuit will have a great influence on the stability of the rectifier system, a power supply isolation scheme consisting of several RC networks is proposed. The rectifier system is implemented in a 65nm general-purpose. Measurement results show that the proposed active-static hybrid V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> compensation scheme achieves a PCE improvement in a wide input power range with a maximum of 8% PCE improvement compared to the active V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> compensation scheme only.

High Fill Factor CsPbI2Br Perovskite Solar Cells Via Crystallization Management

AbstractInorganic CsPbI2Br perovskite has a substantial potential for triple‐junction tandem solar cells as a top subcell, however it exhibits relative instability in the air compared with organic‐inorganic perovskites as well as significantly lower efficiency than the theoretical efficiency limit. To further enhance the air‐stability and efficiency of CsPbI2Br‐based perovskite solar cells (PSCs), it is vitally crucial to improve the crystallinity and passivate the defects within films that accelerate the phase transformation to the photo‐inactive phase in the air. Here, it is reported that crystallization management via incorporating sodium formate (NaFo) in a CsPbI2Br perovskite solution effectively leads to enlarged grain size and the reduced trap density. The Na+ cation and HOOC− anion produce a synergistic effect for engineering the defects by acting as cation and pseudo‐halide anion passivators, respectively. As a result, the NaFo‐incorporating device shows an improved power conversion efficiency (PCE) of 17.7% with a fill factor (FF) of 84.5%. To the best of the authors' knowledge, this progressive FF value is the highest value among CsPbI2Br‐based PSCs reported thus far. In addition, the NaFo‐incorporated device shows improved air stability compared to the control device, retaining over 95% of its initial PCE for 1000 hours under 10% relative humidity at room temperature without any encapsulation.

Optical modelling of TCO based FTO/TiO2 multilayer thin films and simulation in hydrogenated amorphous silicon solar cell

Hydrogenated Amorphous silicon (a:Si:H) has low amounts of defects making it attractive for photovoltaic applications. To improve power conversion efficiency (PCE) of a:Si:H solar cells, this study investigated the effect of introducing FTO/TiO2 multilayer thin films into its structure to serve as antireflection coating. The multilayer thin films were characterized and optimized by optical simulations using a computer program, GLSIM (glazing simulator). The program was written in FORTRAN and implemented in MATLAB. The multi-Fresnel equations were employed to create the GLSIM program. Then using the program, together with the pairs of real and imaginary values of complex refractive index, n and k respectively, the transmittance and reflectance data of FTO/TiO2 multilayer thin films on glass substrate were computed. The optimized FTO/TiO2 multilayer thin films were then incorporated into silicon solar cell with structure glass/FTO/TiO2/n-a-Si:H/i-a-Si:H/p-a:Si:H/P+-BSF and characterized using SCAPS-1D software. The effect of varying layer thickness on the solar cell performance was also investigated. The optimized solar cell had a thickness of 100 nm, 50 nm, 900 nm, 100 nm, 10μm and 5μm for FTO, TiO2, n-a-Si:H, i-a-Si:H, p-a-Si:H and P+-BSF respectively. The device output performance were 37.96 mA/cm2, 1.34 V, 56.37% and 28.72% for Jsc, Voc, FF and η respectively showing a remarkable improvement in the solar cell performance. These results show potential of fabricating an improved hydrogenated silicon solar cell.

High efficiency perovskite/heterojunction crystalline silicon tandem solar cells: towards industrial-sized cell and module

29.2%-conversion efficiency of a two-terminal (2T) perovskite/crystalline Si heterojunction tandem solar cell using 145 μm thick industrial Czochralski (CZ) Si wafer is obtained. The structural optimization, such as surface passivation of the perovskite layer and better light management techniques, improved power conversion efficiency (PCE). To our knowledge, this PCE is the best in 2T-tandem solar cells using CZ wafers. Towards industrialization, crucial issues with the 2T tandem solar cells with crystalline Si bottom cell are discussed. Four-terminal (4T) tandem solar cells are evaluated as an approach to avoid the crucial issues. Examining our base technologies which realize 22.2%-conversion efficiency perovskite single junction solar cell module and 26%-heterojunction back-contact solar cells, we clarified that the based technologies were ready to realize 30%-conversion efficiency 4T perovskite/heterojunction crystalline Si tandem solar cells with approximately quarter size of an industrial crystalline Si solar cell (∼64 cm2).

UV-resistant salicylic acid as interface modifier for efficient and stable perovskite solar cells

Interfacial defect is one of the main hurdles to impede the improvement of efficiency and stability of perovskite solar cells (PSCs). Additionally, the ultraviolet (UV) irradiate induces the generation of deep defects, and further accelerate the decomposition of perovskite films. Thus, the interfacial modification is crucial to improve the efficiency and stability of PSCs. Here, the salicylic acid (SA) as a multifunctional interface material is employed to modify the interface of mesoporous cerium oxide (m-CeOx) and perovskite. The introduced SA molecules can interact with Ce in m-CeOx and Pb in perovskite through carboxylic acid functional groups to passivate interfacial defects and promote interfacial electron extraction and transport. The PSC with SA modification exhibits an improved power conversion efficiency (PCE) of 23.33%. More importantly, the SA can absorb UV light and reduce the damage of UV light to perovskite film, then improving the UV stability and overall stability of devices. This work provides a novel insight to design the interfacial modification materials for preparing efficient and stable PSCs.