- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
The Catalytic Cycle of Water Oxidation in Crystallized Photosystem II Complexes: Performance and Requirements for Formation of Intermediates
摘要： Crystals of Photosystem II (PSII) contain the most homogeneous copies of the water-oxidizing reaction center where O2 is evolved (WOC). However, few functional studies of PSII operation in crystals have been carried out, despite their widespread use in structural studies. Here we apply oximetric methods to determine the quantum efficiency and lifetimes of intermediates of the WOC cycle as a function of added electron acceptors (quinones and ferricyanide), both aerobically and anaerobically. PSII crystals exhibit the highest quantum yield of O2 production yet observed of any native or isolated PSII (61.6%, theoretically 59,000 μmol O2/mg Chl/h). WOC cycling can be sustained for thousands of turnovers using an irreversible electron acceptor (ferricyanide). Simulations of the catalytic cycle identify four distinct photochemical inefficiencies in both PSII crystals and dissolved PSII cores that are nearly the same. The exogenous acceptors equilibrate with the native plastoquinone acceptor at the QB (or QC) site(s), for which two distinct redox couples are observable that regulate flux through PSII. Flux through the catalytic cycle of water oxidation is shown to be kinetically restricted by the QAQB two-electron gate. The lifetimes of the S2 and S3 states are greatly extended (especially S2) by electron acceptors and depend on their redox reversibility. PSII performance can be pushed in vitro far beyond what it is capable of in vivo. With careful use of precautions and monitoring of populations, PSII microcrystals enable the exploration of WOC intermediates and the mechanism of catalysis.
关键词： oxygen-evolving complex,electron acceptors,(micro)crystals,S states,quantum yield,Photosystem II
更新于2025-09-23 15:22:29
-
Effects of the Isomerized Thiophene-Fused Ending Groups on the Performances of Twisted Non-Fullerene Acceptor-Based Polymer Solar Cells.
摘要： Recently, benefiting from the merits of small molecule acceptors (NFAs), polymer solar cells (PSCs) have achieved tremendous advances. From the perspective of the structural characteristics of the π-conjugated acceptor-donor-acceptor (A-D-A)-type of organic molecules, the backbone’s planarity, as well as the terminal groups and their substituents, have strong influences on the performances of the constructed NFAs. Through enlarging the dihedral angle of the conjugated main-chain of NFAs, a certain degree of enhanced photovoltaic parameters have been achieved. To further probe the influences of ending groups on the performances of nonplanar NFAs, we synthesized two new NFAs of i-cc23 and i-cc34 with isomerized thiophene-fused ending groups and twisted π-conjugated main-chain. Compared to the i-cc23 containing 2-(6-oxo-5,6-dihydro-4H-cyclopenta[b]thiophen-4-ylidene)malononitrile ending group, the 2-(6-oxo-5,6-dihydro-4H-cyclopenta[c]thiophen-4-ylidene)malononitrile contained acceptor i-cc34 has a relatively higher molar extinction coefficient, bathochromic-shifted absorption spectrum, and deepened energy levels. When mixed with PBDB-T in solar cells, the i-cc23-based device achieved an excellent open-circuit voltage (VOC) of 1.10 V and a moderated power conversion efficiency of 7.34%. Although the VOC of i-cc34 related device was decreased to 0.96 V, the short-circuit current density and fill factor were improved, giving rise to enhanced efficiency of 9.51%. Apart from the distinct photovoltaic performances, the two isomers-based devices exhibit high radiative efficiency of 8×10-4, leading to a very small non-radiative loss of 0.19 V. Our results emphasize the importance of the isomerized thiophene-fused ending groups on the performances of nonplanar NFAs-based PSCs.
关键词： Twisted small molecular electron-acceptors,Thiophene-fused ending groups,Polymer solar cells,Isomerized end-groups,Non-radiative energy loss
更新于2025-09-23 15:21:01
-
Efficient Organic Solar Cells Based on Non-Fullerene Acceptors with Two Planar Thiophene Fused Perylene Diimide Units
摘要： We designed and synthesized two non-fullerene acceptors (CDT-TFP and C8X-TFP), which comprise a central 4H-cyclopenta[2,1-b:3,4-b’]dithiophene (CDT) as the bridge and two thiophene-fused perylene diimide (TFP) units. The bulky side chains, such as the 4-hexylphenyl side chains, on the CDT bridge can effectively prevent the acceptor molecules from forming large aggregates and the π-π stacking of the terminal planar TFP units can form effective electron transport pathways when blending with the donor polymers. These non-fullerene acceptors are used to fabricate organic solar cells (OSCs) by blending with regioregular middle bandgap polymer reg-PThE. The as-cast devices based on reg-PThE:CDT-TFP show the best PCE of 8.36% with a Voc of 1.10 V, Jsc of 12.43 mA cm-2 and FF of 61.4%; whereas, the analogue PDI dimers (CDT-PDI) that comprising two PDI units bridged with a CDT unit, show only a 2.59% PCE with a Voc of 0.92 V, Jsc of 6.82 mA cm-2 and FF of 41.5%. Our results have demonstrated that non-fullerene acceptors comprising planar PDI units can achieve excellent photovoltaic performance and provide meaningful guidelines for the design of PDI based non-fullerene electron acceptors for efficient OSCs.
关键词： regioregular donor polymer,perylene diimide,organic solar cells,non-fullerene electron acceptors,planar
更新于2025-09-23 15:19:57
-
Terrylene Diimide-Based Middle-Low Bandgap Electron Acceptors for Organic Photovoltaics
摘要： Rylene diimides have evolved as the most investigated compounds among polycyclic aromatic hydrocarbons, due to their excellent absorption, fluorescence and outstanding electron-withdrawing ability. In this work, we present two A-D-A type electron acceptors based on terrylene diimide and investigate the impact of intramolecular nonbonding conformational locks on the molecular geometry, the solid packing arrangement as well as the photovoltaic performance. Detailed investigation demonstrates that the introduction of fluoride atoms facilitates the noncovalent interactions with sulfur elements on adjacent thiophene groups and therefore, more balanced charge transfer as well as suppressed bimolecular recombination prompt the JSC and FF, endowing the solar cells based on fluoride-substituted acceptor with a higher PCE up to 5.29%.
关键词： intramolecular nonbonding conformational locks,electron acceptors,photovoltaic performance,organic photovoltaics,Terrylene diimide
更新于2025-09-23 15:19:57
-
Simultaneously improving the photovoltaic parameters of organic solar cells <i>via</i> isomerization of benzo[ <i>b</i> ]benzo[4,5]thieno[2,3- <i>d</i> ]thiophene-based octacyclic non-fullerene acceptors
摘要： Fused-ring electron acceptors (FREAs) have attracted immense interest owing to their ability for facile structural modification and good thermal and optical characteristics. Among these acceptors, isomerized building blocks originate from multiple reaction sites affect the electronic structures, morphological properties and resulting photovoltaic performance, but have rarely been studied. Herein, three isomeric FREAs, Z1-aa, Z1-ab, and Z1-bb, were synthesized using different reaction sites of benzo[b]benzo[4,5]thieno[2,3-d]thiophene (BTBT)-based fused-ring cores and were used in organic solar cells (OSCs). As compared to Z1-aa and Z1-ab, Z1-bb exhibited red-shifted absorption and a higher maximum molar extinction coefficient. When blended with PM6, Z1-bb-based OSCs exhibited more balanced charge transport compared to those with the PM6:Z1-aa and PM6:Z1-ab blend films, which favored higher short-circuit current density (Jsc) and fill factor (FF). As a result, the OSC devices based on Z1-bb exhibited a power conversion efficiency (PCE) of 12.66% with Voc = 0.98 V, Jsc = 18.52 mA cm-2, and FF = 70.05%, respectively, which are significantly higher than the values recorded for Z1-ab-based (PCE of 9.60%)?and Z1-aa-based (PCE of 4.56%) devices. These results indicate that the isomerization of a fused-ring core originating from a special reaction site could be a promising approach to achieve high-performance OSCs with high Jsc, Voc, and FF.
关键词： Organic solar cells,Isomerization,Fused-ring electron acceptors,BTBT-based fused-ring cores,Photovoltaic performance
更新于2025-09-23 15:19:57
-
The Role of Dipole Moment in Two Fused-Ring Electron Acceptors with One Polymer Donor based Ternary Organic Solar Cells
摘要： Fused-ring electron acceptors (FREAs) based ternary organic solar cells (OSCs) have made significant progress and attracted considerable attention due to their simple device architecture and broad absorption range in devices. There are three key parameters that need to be fine-tuned in ternary OSCs including absorption, energy level and morphology in order to realize high efficiencies. Herein, a series of FREAs with diverse electron-rich cores or electron-deficient terminals are developed and rationally combined to achieve high performance ternary OSCs. A new factor of dipole moment of FREAs’ terminals is unveiled and its working mechanism has been thoroughly investigated by systematical studying of six ternary OSCs. These ternary blends all exhibit complementary absorptions and cascade energy levels, which can facilitate efficient light-harvesting and charge transfer. Additionally, the morphological effects on ternary OSCs are eliminated through comparative studies while demonstrating distinctively different performance. The preliminary results show that compatible dipole moment between two FREAs is critical in ternary blends. Specifically, the performance of the ternary system with two FREAs having quite different dipole moment terminals is worse than that with similar terminal dipole moments. The pair with larger difference in dipole moment will also negatively impact device performance. This interesting phenomenon is likely due to that very different dipole moments of terminals in FREAs can significantly decrease the electron mobility as well as induce unbalanced hole/electron transport. Consequently, it results in increased charge recombination and reduced charge collection efficiency. This finding demonstrates that dipole moment of FREAs should be taken into account in designing ternary OSCs.
关键词： ternary organic solar cells,morphology,dipole moment,charge transfer,Fused-ring electron acceptors
更新于2025-09-23 15:19:57
-
Naphthalene core-based noncovalently fused-ring electron acceptors: effects of linkage positions on photovoltaic performances
摘要： Two mutually isomeric noncovalently fused-ring electron acceptors (NC-FREAs) NOC6F-1 and NOC6F-2 containing two cyclopentadithiophene (CPDT) moieties linked at the 2,6- and 1,5-positions, respectively, of the naphthalene ring were designed and synthesized for organic solar cells (OSCs). Intramolecular noncovalent S···O interactions were introduced into NOC6F-1 and NOC6F-2. The tiny structural variation in NOC6F-1 and NOC6F-2 by just changing the linkage positions affects largely their molecular configuration, absorption, molecular packing, charge transport and photovoltaic performance. Compared to NOC6F-2, NOC6F-1 exhibits smaller distortions between cyclopentadithiophene and the naphthalene unit, leading to an extended conjugation and enhanced p–p stacking. NOC6F-2 exhibits a poor planarity, which restricts the electron delocalization as well as dense p–p stacking in the film form. When blended with PBDB-T, NOC6F-1 exhibits more orderly stacking along both the out-of-plane and in-plane directions than NOC6F-2. OSCs based on PBDB-T:NOC6F-2 merely showed a power conversion efficiency (PCE) of 6.74% with lower Jsc and FF values. OSCs based on NOC6F-1 achieved a higher Jsc of 17.08 mA cm?2 and an FF of 65.79%, thus leading to a significantly enhanced PCE of 10.62%. These results indicate that use of the acceptor molecules with a planar molecular backbone is an important design strategy for NC-FREAs.
关键词： noncovalently fused-ring electron acceptors,charge transport,organic solar cells,photovoltaic performance,molecular configuration
更新于2025-09-12 10:27:22
-
Tailoring and Modifying an Organic Electron Acceptor toward the Cathode Interlayer for Highly Efficient Organic Solar Cells
摘要： With the rapid advance of organic photovoltaic materials, the energy level structure, active layer morphology, and fabrication procedure of organic solar cells (OSCs) are changed significantly. Thus, the photoelectronic properties of many traditional electrode interlayers have become unsuitable for modifying new active layers; this limits the further enhancement in OSC efficiencies. Herein, a new design strategy of tailoring the end-capping unit, ITIC, to develop a cathode interlayer (CIL) material for achieving high power conversion efficiency (PCE) in OSCs is demonstrated. The excellent electron accepting capacity, suitable energy level, and good film-forming ability endow the S-3 molecule with an outstanding electron extraction property. A device with S-3 shows a PCE of 16.6%, which is among the top values in the field of OSCs. More importantly, it is demonstrated that the electrostatic potential difference between the CIL molecule and the polymer donor plays a crucial role in promoting exciton dissociation at the CIL/active layer interface, contributing to additional charge generation; this is crucial for enhancement of the current density. The results of this work not only develop a new design strategy for high-performance CIL, but also demonstrate a reliable approach of density functional theory (DFT) calculation to predict the effect of the CIL chemical structure on exciton dissociation in OSCs.
关键词： organic electron acceptors,cathode interlayers,charge density difference,organic solar cells,high efficiency
更新于2025-09-12 10:27:22
-
Conjugation‐Curtailing of Benzodithionopyran‐Cored Molecular Acceptor Enables Efficient Air‐Processed Small Molecule Solar Cells
摘要： Small molecule solar cells (SMSCs) lag a long way behind polymer solar cells. A key limit is the less controllable morphology of small molecule materials, which can be aggravated when incorporating anisotropic nonfullerene acceptors. To fine-tune the blending morphology within SMSCs, a π-conjunction curtailing design is applied, which produces a efficient benzodithionopyran-cored molecular acceptor for nonfullerene SMSCs (NF-SMSCs). When blended with a molecular donor BDT3TR-SF to fabricate NF-SMSCs, the π-conjunction curtailed molecular acceptor NBDTP-M obtains an optimal power conversion efficiency (PCE) of up to 10.23%, which is much higher than that of NBDTTP-M of longer π-conjunction. It retains 93% of the PCE of devices fabricated in a glove box when all spin-coating and post-treating procedures are conducted in ambient air with relative humidity of 25%, which suggests the good air-processing capability of π-conjunction curtailed molecules. Detailed X-ray scattering investigations indicate that the BDT3TR-SF:NBDTP-M blend exhibits a blend morphology featuring fine interpenetrating networks with smaller domains and higher phase purity, which results in more efficient charge generation, more balanced charge transport, and less recombination compared to the low-performance BDT3TR-SF:NBDTTP-M blend. This work provides a guideline for molecular acceptors’ design toward efficient, low-cost, air-processed NF-SMSCs.
关键词： electron acceptors,all-small-molecule solar cells,air-processing,power conversion efficiency
更新于2025-09-11 14:15:04
-
Designing High Performance Nonfullerene Electron Acceptors with Rylene Imides for Efficient Organic Photovoltaics
摘要： Improving carrier mobility, redox stability, blend morphology, and photovoltaic performance while elucidating structure-property relationships remain important design goals for nonfullerene electron acceptors (NFAs) for organic solar cells. Although numerous NFAs have been created from rylene diimide electron-deficient building blocks, they have showed far inferior photovoltaic properties compared to benchmark fused-ring electron acceptors (FREAs) such as ITIC. Herein we show that new bis(naphthalene-imide)arylenelidenes (BNIAs), incorporating rylene-imide end-capping groups via methine bridges in donor-acceptor architectures, are endowed with enhanced electrochemical redox stability, high carrier mobilities, and high photovoltaic performance. Pairing of those BNIAs that are also FREAs, NIDT and NIBT, respectively with donor polymer PBDB-T produced 10.0-10.8% efficient photovoltaic devices, which are comparable to benchmark ITIC devices. Blends of FREAs NIDT and NIBT and those of non-FREA NITV were found to have similar electron mobility, demonstrating that the much higher photovoltaic efficiency of NIDT and NIBT devices does not originate from enhanced charge transport but from differences in blend morphology and blend photophysics. The results demonstrate that incorporating rylene imides into molecular architectures through methine-bridged donor-acceptor coupling motif is a promising design strategy towards more efficient and electrochemically rugged materials for organic solar cells.
关键词： organic photovoltaics,carrier mobility,redox stability,photovoltaic performance,nonfullerene electron acceptors,rylene imides
更新于2025-09-11 14:15:04