Power Conversion Research Articles

Constructing Multiscale Fibrous Morphology to Achieve 20% Efficiency Organic Solar Cells by Mixing High and Low Molecular Weight D18.

This study underscores the significance of precisely manipulating the morphology of the active layer in organic solar cells (OSCs). By blending polymer donors of D18 with varying molecular weights, a multiscale interpenetrating fiber network structure within the active layer is successfully created. The introduction of 10% low molecular weight D18 (LW-D18) into high molecular weight D18 (HW-D18) produces MIX-D18, which exhibits an extended exciton diffusion distance and orderly molecular stacking. Devices utilizing MIX-D18 demonstrate superior electron and hole transport, improves exciton dissociation, enhances charge collection efficiency, and reduces trap-assisted recombination compared to the other two materials. Through the use of the nonfullerene acceptor L8-BO, a remarkable power conversion efficiency (PCE) of 20.0% is achieved. This methodology, which integrates the favorable attributes of high and low molecular weight polymers, opens a new avenue for enhancing the performance of OSCs.

Bottom Contact Engineering for Ambient Fabrication of >25% Durable Perovskite Solar Cells.

The bottom contact in perovskite solar cells (PSCs) is easy to cause deep trap states and severe instability issues, especially under maximum power point tracking (MPPT). In this study, sodium gluconate (SG) is employed to disperse tin oxide (SnO2) nanoparticles (NPs) and regulate the interface contact at the buried interface. The SG-SnO2 electron transfer layer (ETL) enabled the deposition of pinhole-free perovskite films in ambient air and improved interface contact by bridging effect. SG-SnO2 PSCs achieved an impressive power conversion efficiency (PCE) of 25.34% (certified as 25.17%) with a high open-circuit voltage (VOC) exceeding 1.19V. The VOC loss is less than 0.34V relative to the 1.53eV bandgap, and the fill factor (FF) loss is only 2.02% due to the improved contact. The SG-SnO2 PSCs retained around 90% of their initial PCEs after 1000h operation (T90 = 1000h), higher than T80 = 1000h for the control SnO2 PSC. Microstructure analysis revealed that light-induced degradation primarily occurred at the buried holes and grain boundaries and highlighted the importance of bottom-contact engineering.

Reveal the source of protons in aqueous hydrogen proton battery

In this work, we have discovered and investigated the reaction mechanism of Aqueous Hydrogen Proton Battery (AHPB), which differ from conventional rocking-chair batteries. The hydrogen protons in the battery reaction is provided by the dissociation of H2O molecules in the electrolyte. Thus, the charging and discharging processes of the battery are also accompanied by changes in electrolyte concentration. To explore this, we have designed a AHPBs with a 2 M Zn(ClO4)2 electrolyte. The experimental results demonstrate excellent performance of the AHPBs, with a discharge specific capacity of up to 700.6 mAh g−1 and a charge-discharge power conversion efficiency of 83.638 %. Both experimental and simulation results confirm that H+ in the battery is primarily provided by H2O molecules solvating Zn2+. As the electrolyte concentration increases, ClO4− replaces some of the solvating H2O molecules of Zn2+, resulting in the remaining unsaturated solvating H2O molecules having a stronger propensity for deprotonation, thus facilitating the release of H+. This elucidates the specific source of H+ in AHPBs.

Design optimization and off-design performance analysis of one-dimensional supercritical CO2 Brayton cycle

Supercritical carbon dioxide (SCO2) recompression Brayton cycle (RBC) is an encouraging technology for thermal power conversion and heat harvest for a wide range of heat sources due to its high-efficiency, low auxiliary power consumption, and compact size. However, most studies on its design and off-design performance analysis have been limited to the simple zero-dimensional component models without considering aerothermodynamics and ambient conditions. In this study, we developed a set of fully one-dimensional components models for SCO2 compressors, turbines, and heat exchangers, and, then, applied them to the multi-objective design optimization of a SCO2 cycle targeting a 50 MW net power output. The cycle off-design performance analysis methods and the control strategies were developed to countermeasure the performance degradation against the varying cooling water temperatures and part loads. The multi-objective cycle design optimization demonstrates that the cycle thermal efficiency and total product unit cost can be 0.476 and 11.652$/GJ, respectively, for the 50 MW SCO2 RBC cycle. The choke margin of the main compressor is 0.136 less than that of the re-compressor, and condensation can lead to a sharp decline in efficiency under high-flow conditions, causing the earlier onset of choking. The off-design performance analysis shows that the turbine inlet pressure control improves cycle efficiency below the design point of 317 K but does otherwise above the point. In contrast, inventory control strategies can maintain stable cycle efficiency and achieve adjustable net power output between 10 % and 110 %. The findings have the potential to advance further the commercial application of SCO2 cycles in high-temperature thermal energy systems.

Highly Efficient Wide Bandgap Perovskite Solar Cells With Tunneling Junction by Self-Assembled 2D Dielectric Layer.

Reducing non-radiative recombination and addressing band alignment mismatches at interfaces remain major challenges in achieving high-performance wide-bandgap perovskite solar cells. This study proposes the self-organization of a thin two-dimensional (2D) perovskite BA2PbBr4 layer beneath a wide-bandgap three-dimensional (3D) perovskite Cs0.17FA0.83Pb(I0.6Br0.4)3, forming a 2D/3D bilayer structure on a tin oxide (SnO2) layer. This process is driven by interactions between the oxygen vacancies on the SnO2 surface and hydrogen atoms of the n-butylammonium cation, aiding the self-assembly of the BA2PbBr4 2D layer. The 2D perovskite acts as a tunneling layer between SnO2 and the 3D perovskite, neutralizing the energy level mismatch and reducing non-radiative recombination. This results in high power conversion efficiencies of 21.54% and 19.16% for wide-bandgap perovskite solar cells with bandgaps of 1.7 and 1.8 eV, with open-circuit voltages over 1.3 V under 1-Sun illumination. Furthermore, an impressive efficiency of over 43% is achieved under indoor conditions, specifically under 200 lux white light-emitting diode light, yielding an output voltage exceeding 1 V. The device also demonstrates enhanced stability, lasting up to 1,200 hours.

Influence of terminal moiety on PCE of DSSCs: An In Silico study based on triazatruxene-benzothiadiazole dye

Our study utilized an experimentally synthesized dye as a reference molecule, employing a donor-π linker-acceptor (D-π-A) framework for organic solar cells. The molecule featured a triazatruxene group linked with alkyl branches as the donor and ethynyl benzoic acid as the acceptor, connected through a derivative of benzothiadiazole as the π linker. To improve optoelectronic and photovoltaic properties, ten theoretically designed dyes (ZA1–ZA10) are proposed, differing from the reference (R) by modifying the terminal acceptor moiety. Various quantum analyses, including frontier molecular orbitals, optical properties, reorganization energies, binding energies, transition density matrices (TDM), molecular electrostatic potential (MEP), dipole moment, and density of states were carried out at DFT/B3LYP/6-31G(d,p). Ground state geometries revealed a co-planar morphology in ZA1–ZA10, facilitating efficient charge transportation. TDM and MEP illustrated improved electronic transitions in the excited states. Computational analyses revealed superior photovoltaic properties of ZA1–ZA10. Notably, ZA5 exhibited the most significant redshift (1021 nm) in absorption, lowest bandgap (1.44 eV), smallest transition energy (1.21 eV), least binding energy (0.23 eV), and improved charge mobilities. Results from the adsorption of ZA1-ZA10 on the TiO2 layer confirmed their anchoring potential and effective injection of electrons to anatase (TiO2)9. These significant outcomes promise the potential and novelty of our designed dyes for higher power conversion efficiencies (PCE) in dye-sensitized solar cells (DSSCs).

Lead iodide secondary growth and π-π stack regulation for sequential perovskite solar cells with 23.62% efficiency

The sequential deposited perovskite solar cells (PSCs) have received widespread attention due to its application potential in large-scale perovskite module and perovskite/silicon tandem solar cells. However, insufficient reaction between organic ammonium salts and PbI2 leads to residual PbI2 and low crystallinity of perovskite films, and the fragile Pb-I bonds easily creates iodine loss and reduces the stability of PbI6 framework. In this work, the 4-fluorobenzylamine (FBA) with C = O and –NH2 is employed in PbI2 precursor solution to regulate the secondary growth process of PbI2 film. Due to the low Gibbs free energy and high crystallinity of porous PbI2 film, sufficient reaction between organic ammonium salts and PbI2 is promoted, which results in large-grain, low-defect perovskite films. At the same time, through hydrogen bonding and π-π stacking interactions, the stability of the PbI6 skeleton is effectively improved, significantly suppressing non-radiative recombination and reducing defect state density. Finally, this strategy increases the power conversion efficiency (PCE) of PSCs from 22.06 % to 23.62 %, and the target PSCs maintain 96 % of their initial PCE after being placed in nitrogen for 1300 h.

Fabrication of gradient band tin oxide electron transport layer using self-separated dual-quantum dots for perovskite solar cells

Constructing a gradient band structure electron transport layer (ETL) and thereby enhancing the performance and stability of perovskite solar cells are an effective approach. Leveraging two types of quantum dots (QDs) with different masses, namely GQDs and Au QDs, along with tin oxide (SnO2) colloidal particles, we successfully prepared an ETL with a gradient band structure. Perovskite solar cells fabricated based on this gradient band ETL achieved a power conversion efficiency (PCE) of 22.2%, whereas those prepared with a conventional SnO2 ETL yielded only 19.6% efficiency. Furthermore, under continuous AM 1.5 G and 45°C temperature illumination for 1000 hours, the cells retained 91% of their initial efficiency. Further investigation revealed that the construction of this gradient band structure effectively compensated for the defects of the SnO2, thereby improving its electrical properties. Additionally, it enhanced the transport and separate ability of charge carriers in the ETL, reducing recombination probabilities. This work provides a simple and effective method for constructing gradient band structures, which not only enhances the performance of perovskite solar cells but also holds promise for other photovoltaic conversion devices.

Defect passivation engineering for achieving 4.29% light utilization efficiency MA-free wide-bandgap semi-transparent perovskite solar cells

Wide-bandgap perovskite materials are a great candidate for semitransparent perovskite solar cells (ST-PSCs) due to their tunable bandgap, outstanding transparency, and excellent photovoltaic performance. Though Br-rich perovskite can widen the bandgap, Br influences the crystallization dynamic speed leaving small perovskite grain sizes and high defects. Surface passivation engineering has been one of the best choices to suppress defects caused by the rapid crystallization of Br-rich perovskites. Herein, we applied MA-free perovskite as a light absorber because of the erratic thermal aging of MA-containing perovskites and selected phenethylammonium iodide (PEAI) and 4-trifluoro phenylethylammonium iodide (CF3PEAI) as passivation materials for improving the performance of opaque PSCs and ST-PSCs. Consequently, CF3PEA possesses a larger dipole moment. It has been demonstrated to exhibit a stronger binding energy with the substrate than PEA by density functional theory (DFT) calculations. This enhanced molecular interaction underpins the performance improvements in our solar cells, which manifests as an inverted planar structure opaque PSCs with 1.78 eV bandgap achieve a power conversion efficiency (PCE) of 17.09 % with excellent stability. A PCE of 17.17 % with 25 % average visible-light transmittance (AVT) and 4.29 % light utilization efficiency (LUE) of ST-PSCs is achieved by further optimizing the fabrication process of the buffer layer for protecting the perovskites from the damage of ITO sputter. Meanwhile, a four-terminal tandem solar cell with ST-PSC and silicon-based passivated emitter rear cell (PERC) obtains a PCE of 26.28 %. This work provides a feasible way to fabricate high-performance ST-PSCs with limited materials and preparation conditions.

Surface functionalized porous MXene (Ti3C2Tx)/Polyethyleneimine membrane for efficient osmotic energy conversion

The development of ion-selective membranes is crucial for achieving efficient osmotic power conversion in reverse electrodialysis system. However, balancing ion selectivity and ion permeability in membranes remains a challenge, limiting improvements in energy conversion efficiency for practical applications. In this study, we develop efficient cation exchange membranes by integrating versatile aromatic hydroxyl groups with MXene nanosheets and polyethyleneimine (PEI) into their lamellar structure. This approach holds promise for achieving non-swelling, high selectivity, and enhanced power density for osmotic energy conversion. The abundance positive surface charge within PEI molecules, combined with the 2D sub-nanochannels of MXene nanosheets, facilitates the biomimetic replication of channel size, chemical groups, and adjustable charge density in the resulting membranes. The fabrication of these membranes is easily achieved through simple hydrothermal, functionalization, and surface-charged techniques, suggesting promising scalability. These membranes exhibit remarkable stability against swelling in aqueous solutions for up to 25 days and demonstrate a high selectivity of 0.95 and a superior output power density of 18.3 W/m2 in artificial river water and seawater.

Studying the effect of ambient temperature variations on perovskite precursor film formation using different antisolvents

This study investigates the sensitivity of two antisolvents to ambient temperature fluctuations during the fabrication of triple-cation perovskite thin films. Chlorobenzene (CB) and ethyl acetate (EA) were employed as antisolvents in the preparation of perovskite solar cells (PSCs) under identical ambient temperature variation conditions. The experimental results reveal that the quality of the perovskite films does not exhibit a consistent trend in response to ambient temperature changes depending on the antisolvent used. When CB was used as the antisolvent, the highest-performing device, produced at an ambient temperature of 18 °C, achieved a power conversion efficiency (PCE) of 19.9 %. In contrast, when EA was employed as the antisolvent, the highest-performing device was fabricated at 25 °C, reaching a PCE of 20.5 %. Furthermore, when the ambient temperature exceeded 30 °C, all films prepared with either antisolvent exhibited significant cracking, indicating that elevated temperatures adversely affect perovskite film formation. To further investigate the mechanism through which ambient temperature affects the film-forming process, antisolvents at varying temperatures were used during perovskite film preparation to simulate transient temperature increases during formation. This study reveals that the impact of ambient temperature variations on perovskite film formation does not exhibit a uniform trend but is significantly influenced by the choice of antisolvent. Moreover, this work offers valuable insights for optimizing the fabrication of high-quality perovskite thin films.

Probing the Impact of Four BSF Layers on MASnI3‐Based Lead‐Free Perovskite Solar Cells for >33% Efficiency

AbstractThis study systematically investigates the impact of various layers of the back surface field (BSF) on the performance of CH₃NH₃SnI₃ (MASnI₃)‐based lead‐free mixed organic–inorganic halide perovskite solar cells. By employing SCAPS‐1D (Solar Cell Capacitance Simulator in One Dimension) simulation software, the behavior of solar cells is analyzed incorporating BSF layers of CuI, NiO, ZnTe, and CBTS. The findings indicate that the inclusion of these BSF materials significantly enhances power conversion efficiency (PCE), with CBTS showing the highest PCE of 33.57%. The energy band diagrams reveal that the BSF layers effectively reduce recombination losses at the rear interface and improve charge carrier collection. Detailed analysis of photovoltaic parameters, such as open‐circuit voltage (Voc), short‐circuit current density (Jsc), fill factor (FF), and overall PCE, underscores the superiority of CBTS as optimal BSF materials. Temperature variation studies demonstrate that CBTS maintains superior performance across a range of temperatures, highlighting its potential for high‐efficiency, thermally stable perovskite solar cells. This comprehensive investigation provides valuable insights for optimizing the design and performance of MASnI₃‐based perovskite solar cells, with the aim of efficiencies greater than 33%.

All-fiber coherent supercontinuum generation in a cascade of silica, fluoride, and chalcogenide fibers

Abstract We present an all-fiber coherent supercontinuum spanning the spectral range of 1.7–5.0 µm from a cascade of silica, ZBLAN, and chalcogenide (ChG) nonlinear fibers (NLFs). Coherence is maintained by the combined use of femtosecond pump pulses as well as by allowing deterministic spectral broadening mechanism at every stage of the cascade. The use of femtosecond pump pulses enables avoiding modulation instability (MI) at the onset of the supercontinuum generation process and thus prevent subsequent MI-seeded random noise. Once in the NLF cascade, the pump pulse is instead converted into a soliton of order maintained at N < 6 in the silica and ZBLAN NLFs, ensuring soliton fission followed by self-frequency shift of a few solitons. Finally, in the ChG NLF, spectral broadening is facilitated through self-phase modulation and dispersive wave generation. The deterministic nature of these nonlinear phenomena results in the generation of a coherent supercontinuum. The supercontinuum delivers an average power of 54 mW from an average pump power of 300 mW, yielding a power conversion efficiency of 18%. The experimental results closely align with numerical simulations, from which coherence is estimated. Such a coherent supercontinuum with a megahertz repetition rate is essential for spectroscopic systems based on optical frequency combs and applications in high-precision optical coherence tomography.

Silicon heterojunction back contact solar cells by laser patterning.

Back contact silicon solar cells, valued for their aesthetic appeal by removing grid lines on the sunny side, find applications in buildings, vehicles and aircrafts, enabling self-power generation without compromising appearance1-3. Patterning techniques arrange contacts on the shaded side of the silicon wafer, offering benefits for light incidence as well. However, the patterning process complicates production and causes power loss. Here we employ lasers to streamline back contact solar cell fabrication and enhance power conversion efficiency. Our approach produces the first silicon solar cell to exceed 27% efficiency. Hydrogenated amorphous silicon layers are deposited on the wafer for surface passivation and collection of light-generated carriers. A dense passivating contact, diverging from conventional technology practice, is developed. Pulsed picosecond lasers at different wavelengths are used to create back contact patterns. The developed approach is a streamlined process for producing high-performance back contact silicon solar cells, with a total effective processing time of about one-third that of emerging mainstream technology. To meet terawatt demand, we develop rare indium-less cells at 26.5% efficiency and precious silver-free cells at 26.2% efficiency. The integration of solar solutions in buildings and transportation is poised to expand with these technological advancements.

Synergistic charge-transfer dynamics of novel benzothiadiazole-based donor materials for higher power conversion efficiency: From structural engineering to efficiency assessment in non-fullerene organic solar cells

In the realm of organic solar cell technology, current research is dedicated to enhancing the photovoltaic properties of donor-π-acceptor (D-π-A) materials to achieve higher power conversion efficiencies (PCE). This optimization focuses particularly on fine-tuning the conduction band and electrolytic characteristics to maximize performance. Addressing the growing demand for novel materials with enhanced optoelectronic properties in organic photovoltaic research, our proposed compound BT05, one of nine new benzothiadiazole-based D-π-A donor molecules (BT01-BT09), exhibits a power conversion efficiency (PCE) of 25%, surpassing the 18% PCE of the reference compound BTD-OMe. TD-DFT and DFT simulations illuminate how donor modifications enhance the photovoltaic characteristics of the proposed molecules. Higher open-circuit voltage (VOC) of 1.74-2.26 V, increase in binding energy (∼1.997), λmax (470-476 nm), reduction in energy gap (4.25-4.65 eV), also validates the PCE results and confirm the usefulness of designed molecules (BT01-BT09). Moreover, DHOMO and ALUMO, TDM, reorganization energy λe (0.0124-0.0134) and λh (0.0094-0.0098), and NPA results also confirm that BT01-BT09 molecules unlock the organic solar cell's potential and advance sustainable energy solutions through innovative technology. Among all developed compounds, BT05 displays higher VOC (2.26 V), 87% fill-factor, and 25% PCE; hence, it is recommended in future solar cell applications.

Exploring 32 % efficiency of eco-friendly kusachiite-based solar cells: A numerical study

Recently, solar cells have appeared as a promising solution to meet the increasing energy demand. However, their large-scale commercial use is limited by issues such as toxicity (Cd, Pb, etc), high manufacturing costs, lower stability, and low efficiency. In this perspective, kusachiite solar cells (KSCs) are environmentally friendly, long-term stable, and easy to manufacture. Thus, in this work, kusachiite (CuBi2O4) is used as an absorber layer, with NiO and SrTiO3 serving as the hole transport material (HTM) and an electron transport layer (ETL), respectively. The KSCs, with a structure of FTO/SrTiO3/CuBi2O4/NiO/Au, are numerically simulated. Maximum power conversion efficiency is achieved by optimizing several photovoltaic parameters, such as the thickness and doping density of the ETL, absorber, and HTM. The optimized thicknesses for the HTL, absorber layer, and ETL are 1.5 μm, 2.28 μm, and 0.02 μm, respectively. The designed KSCs exhibit an efficiency eta (η) of 31.89 %, an open-circuit voltage (Voc) of 1.31 V, a short-circuit current (Jsc) of 28.58 mA/cm2, and a fill factor (FF) of 84.99 %.

Low-temperature crosslinked hole transport material for high-performance inverted perovskite solar cells

Hole transport materials (HTMs) play a crucial role in the development of high-performance inverted perovskite solar cells (PSCs) by facilitating hole transport, passivating defects, and tuning crystallization. Achieving high efficiency and stability remains a key challenge for the PSCs. Crosslinked HTMs combine the efficiency of small molecules with enhanced environmental stability, however, a significant challenge in developing crosslinked HTMs for PSCs is the high temperature required for crosslinking. In this work, we synthesized a concise crosslinkable HTM, Tetrastyrenebiphenyldiamine (TPDA), based on a biphenyl core with four styrene groups, using a one-step method. TPDA can be crosslinked through an annealing process at 100℃ for 10 min without the need for any dopants or initiators. Interestingly, the compact films formed in the anneal process and the excellent spreadability for the perovskite precursor solution leading to the high-quality perovskite films, as a result, the inverted devices based on CL-TPDA achieve a champion power conversion efficiency (PCE) of 21.4%. Furthermore, the stability of the devices without encapsulation has notably improved. The PCE maintains over 85% of its initial value after 1000 h of storage in ambient air (25℃, relative humidity about 50%).

High performance Bi-facial dye sensitized solar cells developed using MXenes assisted novel photoelectrode design

A new device architecture of bi-facial dye sensitized solar cell (DSSC) is designed, fabricated by use of novel photoelectrode design contains MXenes. The developed bi-facial DSSC witnessed higher power conversion efficiency (PCE) of 12.82 % with short-circuit current density (JSC) of 27.46 mA/cm2. The DSSC revealed 9.74 % of PCE by front side illumination and 4.57 % by back side illuminations. The results motivated to develop mini-module of series connected 12 test cells, which results in 13.34 % of PCE.

Boosting the power conversion efficiency of hybrid triboelectric-photovoltaic cells through the field coupling effect

Boosting the power conversion efficiency of hybrid triboelectric-photovoltaic cells through the field coupling effect

New family of two-dimensional A2B2C5 single-layer with high carrier mobilities and excellent conversion efficiency for solar cells

Screening high-performance two-dimensional (2D) materials with desirable direct band gaps and high mobility has attracted great interest due to their excellent application in 2D field effect transistors. Herein, we predicted a new family of nine-atomic A2B2C5 (A = Mg, Ba; B= Al, Ga, and In, C = S, Se) single-layer using first-principles calculations. The results indicate that the energies of this A2B2C5 single-layer are slightly lower than that of exfoliated single-layer Mg2Al2S5. Furthermore, most of the A2B2C5 single-layers host not only direct band gaps but also outstanding electron mobilities (up to ∼103 cm2V−1s−1), revealing a desirable range of near-infrared to visible light absorption. Importantly, single-layer Ba2Al2Se5 and Mg2Ga2Se5 are good donor materials, the corresponding Ba2Al2Se5/HfS2 and Mg2Ga2Se5/InS type-II heterostructures exhibit promising power conversion efficiencies of 22.3 % and 19.8 %, respectively. Our work provides some competitive A2B2C5 candidate single-layers for applying high-performance solar cells.