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Role of CdSe and CdSe@ZnS quantum dots interlayers conjugated in inverted polymer solar cells
摘要： We demonstrate the use of CdSe quantum dots (QDs) as an interlayer for improving photovoltaic performance in the inverted polymer solar cells (iPSCs). The conjugation of CdSe and CdSe@ZnS core@shell QDs between polyethylenimine ethoxylated (PEIE) polymer and PTB7:PC71BM blended layer played an important role in increasing the short circuit current density by F€orster resonance energy transfer (FRET) and efficient charge transport. The drastic mutual photoluminescence quenching suggests that the photon energy absorbed by PTB7:PC71BM are effectively transferred to the QDs. The PTB7:PC71BM based iPSCs with the CdSe QDs interlayer exhibits higher power conversion efficiency of 8.13%, which is 13.4% higher than that of the control device. The iPSCs with CdSe@ZnS QDs interlayer showed relatively lower PCE of 7.31%, which could be due to an increase in carrier recombination inside QDs by relatively high energy level of ZnS shell. As a consequence, the enhanced photovoltaic performance of iPSCs with CdSe QDs interlayer can be attributed to an effective charge transport and an increase in the overall photocurrent by FRET.
关键词： Carrier transport,Resonance energy transfer,Quantum dots,Inverted polymer solar cells,CdSe,Energy level alignment
更新于2025-09-23 15:21:01
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Enhanced Efficiency and Stability of Nonfullerene Ternary Polymer Solar Cells Based on Spontaneously Assembled Active Layer: The Role of a High Mobility Small Molecular Electron Acceptor
摘要： It is challenging to afford efficient and stable organic solar cells based on the as-cast active layer without any external treatments. We present a planar organic electron acceptor BPTCN with high electron mobility as a third component in nonfullerene ternary polymer solar cells, which comprises an electron-deficient 4,7-bis(5H-4,6-dioxothieno[3,4-c]pyrrol-1-yl)benzo[c][1,2,5]thiadiazole core, doubly endcapped by 2-(3-ethyl-5-methylene-4-oxothiazolidin-2-ylidene)malononitrile through the alkylated thiophene-2,5-ylene unit. It shows a π-π stacking distance of 3.60 ? and μe of 1.31 × 10?3 cm2 V?1 s?1. BPTCN exhibits an absorption maximum at 569 nm in the as-cast film and good miscibility with the NIR-absorption acceptor COi8DFIC, leading to complete f?rster energy transfer in the blends. Adding BPTCN into the PTB7-Th:COi8DFIC blend produces multiple beneficial effects: i) facilitating exciton dissociation and charge transfer at the donor/acceptor interface while suppressing bimolecular and trap-assisted recombination by analysis of the Jph–Veff, Jsc–Ilight and Voc–Ilight characteristics, ii) increasing hole and in particular electron transport; and iii) generally promoting the crystallinity of the polymer donor PTB7-Th, as revealed by grazing incidence X-ray diffraction. Moreover, the phase purity is greatly improved in the ternary blend PTB7-Th:COi8DFIC:BPTCN (1:1.05:0.45 by weight). Consequently, the tentatively optimized ternary solar cell provides a PCE of 11.62% with Voc = 0.74 V, Jsc = 25.93 mA cm-2 and FF = 60.61% in comparison with the binary systems PTB7-Th:COi8DFIC (PCE of 9.41%) and PTB7-Th:BPTCN (6.42%) in the absence of any extra treatments. After thermal aging at 80 oC for 450 h, this ternary solar cell exhibits increased stability with PCE retaining 84.39% of the initial value.
关键词： PTB7-Th,COi8DFIC,BPTCN,electron acceptor,organic solar cells,thermal stability,nonfullerene ternary polymer solar cells
更新于2025-09-23 15:19:57
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10.13% Efficiency Alla??Polymer Solar Cells Enabled by Improving the Optical Absorption of Polymer Acceptors
摘要： All-polymer solar cells (all-PSCs) are one of the most promising flexible and wearable energy generators due to their excellent morphology stability and mechanical robustness. However, it has been limited light absorption capacity for most polymer acceptors that hinders the improvement of power conversion efficiency (PCE) of all-PSCs. Herein, by simultaneously increasing the conjugation of the acceptor unit and enhancing the electron-donating ability of the donor unit, a novel narrow-bandgap polymer acceptor PF3-DTCO based on a A-D-A-structured acceptor unit ITIC16 and a carbon-oxygen (C-O)-bridged donor unit DTCO was developed. Extended conjugation of the acceptor units from IDIC16 to ITIC16 result in a red-shifted absorption spectrum and improved absorption coefficient without significant LUMO level reduction. Moreover, in addition to further broadening the absorption spectrum by the enhanced intramolecular charge transfer effect, the introduction of C-O-bridges into donor unit improves the absorption coefficient and electron-mobility, as well as optimizes the morphology and molecular order of active layers. As a result, the PF3-DTCO achieved a higher PCE of 10.13% with a higher short-circuit current density (Jsc) of 15.75 mA cm-2 in all-PSCs compared to its original polymer acceptor PF2-DTC (PCE=8.95% and Jsc=13.82 mA cm-2). Our work provides a promising method to construct high-performance polymer acceptors with excellent optical absorption for efficient all-PSCs.
关键词： optical absorption,all-polymer solar cells,polymer acceptor,carbon-oxygen-bridging,power conversion efficiency
更新于2025-09-23 15:19:57
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Effects of a Fluorinated Donor Polymer on the Morphology, Photophysics, and Performance of All-Polymer Solar Cells based on Naphthalene Diimide-Arylene Copolymer Acceptors
摘要： Naphthalene diimide (NDI)-biselenophene copolymer (PNDIBS) and NDI-selenophene copolymer (PNDIS) and the fluorinated donor polymer PM6 were used to investigate how a fluorinated polymer component affects the morphology and performance of all-polymer solar cells (all-PSCs). Although the PM6:PNDIBS blend system exhibits a high open-circuit voltage (Voc = 0.925 V) and desired low optical bandgap energy loss (Eloss = 0.475 eV), the overall power conversion efficiency (PCE) was 3.1%. In contrast, PM6:PNDIS blends combine a high Voc (0.967 V) with a high fill factor (FF = 0.70) to produce efficient all-PSCs with 9.1% PCE. Furthermore, the high performance PM6:PNDIS all-PSCs could be fabricated by various solution processing approaches and at active layer thickness as high as 300 nm without compromising photovoltaic efficiency. The divergent photovoltaic properties of PNDIS and PNDIBS when paired respectively with PM6 are shown to originate from the starkly different blend morphology and blend photophysics. Efficient PM6:PNDIS blend films were found to exhibit a vertical phase stratification along with lateral phase separation while the molecular packing had a predominant face-on orientation. Bulk lateral phase separation with both face-on and edge-on molecular orientations featured in the poor performing PM6:PNDIBS blend films. Enhanced charge photogeneration and suppressed geminate and bimolecular recombinations with 99% charge collection probability found in PM6:PNDIS blends strongly differ from the poor charge collection probability (66%) and high electron-hole pair recombination seen in PM6:PNDIBS. Our findings demonstrate that beyond the generally expected enhancement of Voc, a fluorinated polymer component in all-PSCs can also exert a positive or negative influence on photovoltaic performance via the blend morphology and blend photophysics.
关键词： Naphthalene Diimide-Arylene Copolymer,Fluorinated donor polymer,Vertical phase stratification,All-polymer solar cells,Thick-film active layer,Blend Morphology
更新于2025-09-23 15:19:57
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Highly efficient ternary polymer solar cell with two non-fullerene acceptors
摘要： Polymer solar cells (PSCs) based on binary and ternary active layers were built using PBDB-T polymer as donor and two non-fullerene acceptors (MPU2 and MPU3) with different DPP cores and terminal units but different conjugation length. The studied binary PSCs showed PCE (power conversion efficiency) values of 8.22% (PBDB-T:MPU2) and 9.77% (PBDB-T:MPU3). The VOC measured using the MPU3-based acceptor was higher than that obtained using MPU2 – this difference is attributed to a higher LUMO energy level of MPU3. MPU2 and MPU3 present complementary absorptions in the wavelength range where PBDB-T exhibits a poor absorption, thus the combination of these materials offers great potential for the fabrication of ternary PSCs. The solar cell with an optimized ternary layer PBDB-T:MPU2:MPU3 (1:1:1) showed an PCE value of 10.78%, higher than those obtained for the binary devices due to the enhanced of JSC and FF values. And, since the emission of MPU3 partially overlaps with the absorption of MPU2, the transfer of energy from MPU3 to MPU2 can improve the exciton utilization efficiency and achieve enhanced overall power conversion efficiency in this ternary solar cell.
关键词： Polymer donor,Power conversion efficiency,Non-fullerene acceptor,Ternary polymer solar cells
更新于2025-09-23 15:19:57
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Over 15% Efficiency Polymer Solar Cells Enabled by Conformation Tuning of Newly Designed Asymmetric Smalla??Molecule Acceptors
摘要： The prosperous period of polymer solar cells (PSCs) has witnessed great progress in molecule design methods to promote power conversion efficiency (PCE). Designing asymmetric structures has been proved effective in tuning energy level and morphology, which has drawn strong attention from the PSC community. Two hepta-ring and octa-ring asymmetric small molecular acceptors (SMAs) (IDTP-4F and IDTTP-4F) with S-shape and C-shape confirmations are developed to study the relationship between conformation shapes and PSC efficiencies. The similarity of absorption and energy levels between two SMAs makes the conformation a single variable. Additionally, three wide-bandgap polymer donors (PM6, S1, and PM7) are chosen to prove the universality of the relationship between conformation and photovoltaic performance. Consequently, the champion PCE afforded by PM7: IDTP-4F is as high as 15.2% while that of PM7: IDTTP-4F is 13.8%. Moreover, the S-shape IDTP-4F performs obviously better than their IDTTP-4F counterparts in PSCs regardless of the polymer donors, which confirms that S-shape conformation performs better than the C-shape one. This work provides an insight into how conformations of asymmetric SMAs affect PCEs, specific functions of utilizing different polymer donors to finely tune the active-layer morphology and another possibility to reach an excellent PCE over 15%.
关键词： small-molecule acceptors,power conversion efficiencies,polymer solar cells
更新于2025-09-23 15:19:57
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Simultaneous improvement of three parameters using binary processing solvent approach in as-cast non-fullerene solar cells
摘要： As-cast polymer solar cells without any additive and pre- or post-treatment principally are of high compatibility with mass production technologies, whose efficiencies are typically promoted by new donor and acceptor materials. In this work, a binary solvent approach using chloroform (CF) of low boiling point as good solvent for both polymer donor PTQ10 and non-fullerene acceptor IT-4Cl and mesitylene (MES) of relatively high boiling point as a semi-orthogonal co-solvent due to weaker solubility to the acceptor is explored. Due to the selective orthogonality of MES to the IT-4Cl acceptor, an optimized morphology has been realized for the as-cast device based on the PTQ10:IT-4Cl blend, which leads to a simultaneous improvement in the open-circuit voltage, short-circuit current, and fill factor, finally achieving a high as-cast efficiency of over 13%. Furthermore, the as-cast devices fabricated with the binary solvent can exhibit good air stability and great accessibility in large area cells. Our findings provide an alternative guideline for the optimization of the as-cast polymer solar cells.
关键词： polymer solar cells,morphology optimization,non-fullerene acceptor,binary solvent,as-cast
更新于2025-09-23 15:19:57
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Solutiona??Processed Polymer Solar Cells with over 17% Efficiency Enabled by an Iridium Complexation Approach
摘要： The commercially available PM6 as donor materials are used widely in highly efficient nonfullerene polymer solar cells (PSCs). In this work, different concentrations of iridium (Ir) complexes (0, 0.5, 1, 2.5, and 5 mol%) are incorporated carefully into the polymer conjugated backbone of PM6 (PM6-Ir0), and a set of π-conjugated polymer donors (named PM6-Ir0.5, PM6-Ir1, PM6-Ir2.5, and PM6-Ir5) are synthesized and characterized. It is demonstrated that the approach can rationally modify the molecular aggregations of polymer donors, effectively controlling the corresponding blend morphology and physical mechanisms, and finally improve the photovoltaic performance of the PM6-Irx-based PSCs. Among them, the best device based on PM6-Ir1:Y6 (1:1.2, w/w) exhibits outstanding power conversion efficiencies (PCEs) of 17.24% tested at Wuhan University and 17.32% tested at Institute of Chemistry, Chinese Academy of Sciences as well as a certified PCE of 16.70%, which are much higher than that of the control device based on the PM6-Ir0:Y6 blend (15.39%). This work affords an effective approach for further break through the reported champion PCE of the binary PSCs.
关键词： iridium complexation,morphology,polymer solar cells,power conversion efficiency
更新于2025-09-23 15:19:57
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Synthesis and Characterization of Wide-Bandgap Conjugated Polymers Consisting of Same Electron Donor and Different Electron-Deficient Units and Their Application for Nonfullerene Polymer Solar Cells
摘要： Substantial development has been made in nonfullerene small molecule acceptors (NFSMAs) that has resulted in a significant increase in the power conversion efficiency (PCE) of nonfullerene-based polymer solar cells (PSCs). In order to achieve better compatibility with narrow-bandgap nonfullerene small molecule acceptors, it is important to design the conjugated polymers with a wide bandgap that has suitable molecular orbital energy levels. Here two donor–acceptor (D–A)-conjugated copolymers are designed and synthesized with the same thienyl-substituted benzodithiophene and different acceptors, i.e., poly{(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)-alt-(1,3-bis(2-octyldodecyl)-1,3-dihydro-2H-dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2-d]imidazol-2-one-5,8-diyl)} (DTBIA, P1) and poly{(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)-alt-(2-(5-(3-octyltridecyl)thiophen-2-yl)dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2-d]thiazole-5,8-diyl)} (TDTBTA, P2) (and their optical and electrochemical properties are investigated). Both P1 and P2 exhibit similar deeper highest occupied molecular orbital energy level and different lowest unoccupied molecular orbital energy level. Both the copolymers have complementary absorption with a well-known nonfullerene acceptor ITIC-F. When blended with a narrow-bandgap acceptor ITIC-F, the PSCs based on P1 show a power conversion efficiency of 11.18% with a large open-circuit voltage of 0.96 V, a Jsc of 16.89 mA cm?2, and a fill factor (FF) of 0.69, which is larger than that for P2 counterpart (PCE = 9.32%, Jsc = 15.88 mA cm?2, Voc = 0.91 V, and FF = 0.645). Moreover, the energy losses for the PSCs based on P1 and P2 are 0.54 and 0.59 eV, respectively. Compared to P2, the P1-based PSCs show high values of incident photon to current conversion efficiency (IPCE) in the shorter-wavelength region (absorption of donor copolymer), more balanced hole and electron mobilities, and favorable phase separation with compact π–π stacking distance.
关键词： solvent vapor annealing,polymer solar cells,nonfullerene acceptors,wide-bandgap polymers
更新于2025-09-23 15:19:57
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Thiophene- and Carbazole-Substituted N-Methyl-Fulleropyrrolidine Acceptors in PffBT4T-2OD Based Solar Cells
摘要： The impact of fullerene side chain functionalization with thiophene and carbazole groups on the device properties of bulk-heterojunction polymer:fullerene solar cells is discussed through a systematic investigation of material blends consisting of the conjugated polymer poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3?-di(2-octyldodecyl)-2,2′;5′,2″;5″,2?-quaterthiophen-5,5?-diyl)] (PffBT4T-2OD) as donor and C60 or C70 fulleropyrrolidines as acceptors. The photovoltaic performance clearly depended on the molecular structure of the fulleropyrrolidine substituents although no direct correlation with the surface morphology of the photoactive layer, as determined by atomic force microscopy, could be established. Although some fulleropyrrolidines possess favorable lowest unoccupied molecular orbital levels, when compared to the standard PC71BM, they originated OPV cells with inferior efficiencies than PC71BM-based reference cells. Fulleropyrrolidines based on C60 produced, in general, better devices than those based on C70, and we attribute this observation to the detrimental effect of the structural and energetic disorder that is present in the regioisomer mixtures of C70-based fullerenes, but absent in the C60-based fullerenes. These results provide new additional knowledge on the effect of the fullerene functionalization on the efficiency of organic solar cells.
关键词： regioisomers,polymer solar cells,fulleropyrrolidine acceptors,stereoisomers,C70 mono-adducts
更新于2025-09-23 15:19:57