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Toward reliable high performing organic solar cells: Molecules, processing, and monitoring
摘要： A steady surge in device efficiencies of organic solar cells (OSCs) along with improvement in associated features, such as stability and facile processing methods, is expected to provide a realistic, feasible commercial option. The introduction of high performing donor and acceptor molecules along with tailored buffer layers has provided the impetus for the resurgence of this field. Further options of ternary and tandem architectures of these OSC systems should push this technology to competitive levels. A major hurdle, which is expected when these devices are evaluated for long-term performance in all weather conditions, is the level of degradation. We examine and address these stability-limiting factors in this perspective article. Modifications in microstructure/morphology and interfaces with time and energy levels defining the molecules form some of the critical intrinsic degradation pathways. Various strategies that have been used to limit the associated pathways of degradation of the active layer will be discussed. One such strategy is electric field-assisted thermal annealing treatment, which concomitantly also brings in a favorable vertical phase segregated active layer morphology. We also emphasize the utility of photocurrent noise measurements to monitor the level of degradation and possibly forecast the trajectory of long-term performance of OSCs.
关键词： processing methods,photocurrent noise measurements,electric field-assisted thermal annealing,device efficiencies,degradation,donor and acceptor molecules,organic solar cells,stability,ternary and tandem architectures
更新于2025-09-23 15:19:57
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Characterization of spray deposited ternary ZnSxSe(1-x) thin films for solar cell buffers
摘要： This paper reports on cadmium free, environment friendly, industrially beneficial, chemically sprayed ZnSxSe(1-x) (ZSS) thin films with tunable band gap which is suitable for various optoelectronic applications including buffer layer in solar cells. Chemically sprayed ZSS thin films with x ranging from 0 to 1 were studied extensively by adopting the characterization techniques like X-ray diffractometry (XRD), Scanning electron microscopy with energy dispersive spectroscopy (SEM-EDAX), Ultraviolet – visible (UV–VIS), Photoluminescence (PL) and Raman spectroscopies in order to assess the suitability of the formed thin film for the buffer layer applications. XRD analysis was done to determine various parameters like lattice constant, crystallite size, strain and dislocation density. From lattice constant, Vegard's law was also verified and compared the composition estimation with EDAX data. Refractive index was compared using Vandemme model with the values obtained using reflectance data. Photoluminescence and Raman spectra were analyzed to get an insight on structural defects, which have major role in deciding the electrical properties. Electrical properties were assessed by estimating carrier concentration, carrier mobility and electrical resistivity by adopting Van der Pauw technique. Based on structural, optical and electrical properties, sample with x = 0.4 is suggested for the buffer layer application in CIGS based solar cells, which produces minimum lattice mismatch with considerably high optical transmittance and electrical conductance.
关键词： Ternary chalcogenide,Thin films,Spray pyrolysis,Solar cell,Photoluminescence,Raman spectroscopy
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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Significance of Dopant/Component Miscibility to Efficient N-Doping in Polymer Solar Cells
摘要： The uncertain dopant location in the bulk heterojunction (BHJ) film hinders the wide application of molecular doping in polymer solar cells (PSCs) as is in other organic devices. It is known that the interaction between dopant and component governs the dopant distribution in the BHJ film, and thus largely controls the effectiveness of molecular doping. After excluding the strong dopant/component interaction by forming the charge-transfer complex in solution, we estimate the dopant/component miscibility by calculating the difference of Hansen’s total solubility parameters (δi-Hansen) and prove its correctness by contact angle measurements, and two model systems of poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophe-2-yl)-benzo[1,2-b:4,5-b’]dithiophene))-alt-(5,5-(1’,3’-di-2-thienyl -5’,7’-bis(2-ethylhexyl)benzo[1’,2’-c:4’,5’-c’]dithiophene-4,8-dione))] (PBDB)/poly{[N,N’-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5’-(2,2’-bithiophene)} (N2200) and poly[4,8-bis(5-(2-ethylhexyl)-thiophene-2-yl)benzo[1,2-b;4,5-b’]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl]] (PCE10)/N2200 are selected to reveal the miscibility-photovoltaic performance relations. Only the material combination with large δi-Hansen between n-dopant (4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl) phenyl) dimethylamine (N-DMBI) and the donor polymer achieves enhanced photovoltaic performance. After that, we examine the doped morphology of polymer blends. Since the polymers’ crystallizations are negatively affected by N-DMBI addition, we ensure the significance of n-doping on the enhanced device performance. Besides the dopant/polymer interaction, the solvent/polymer and solvent/dopant interactions are also considered to evaluate the kinetic effect on N-DMBI distribution by drawing the ternary phase diagram. We conclude that the kinetic morphological evolution doesn’t change the miscibility governed N-DMBI distribution in the BHJ film. Finally, we provide a direct relationship between the N-DMBI position and the device property by fabricating the bi-layer devices. The enhancement of photovoltaic performances is observed in both of material systems only if the N-DMBI distributes in N2200. Our work outlines a basis for using the dopant/component interaction and ternary phase diagram to predict the dopant distribution before extensive experiments. It significantly reduces the trial-to-error work and increases the reliability of molecularly doped PSCs.
关键词： n-doping,polymer solar cell,doped morphology,ternary phase diagram,Molecular doping
更新于2025-09-23 15:19:57
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High-Performance Ternary Organic Solar Cells with Controllable Morphology via Sequential Layer-by-Layer Deposition
摘要： Ternary blending of light harvesting materials has been proven to be a potential strategy to improve the efficiency of solution processed organic solar cells (OSCs). However, the optimization of ternary system is usually more complicated than the binary one as the morphology of conventional ternary blend films is very difficult to control, thus undermining the potential of ternary OSCs. Herein, we report a general strategy for better control of the morphology of ternary blend films composed of a polymer donor and two non-fullerene small molecule acceptors for high-performance OSCs using sequential layer-by-layer (LbL) deposition method. The resulted LbL films form bicontinuous interpenetrating network structure with high crystallinity of both the donor and acceptor materials, showing efficient charge generation, transport and collection properties. In addition, the power conversion efficiencies (PCEs) of the ternary LbL OSCs are less sensitive to the blending ratio of the third component acceptor, providing more room to optimize the device performance. As a result, optimal PCEs of over 11%, 13 % and 16 % were achieved for the LbL OSCs composed of PffBT4T-2OD/IEICO-4F:FBR, PBDB-T-SF/IT-4F:FBR and PM6/Y6:FBR, respectively. Our work provides useful and general guidelines for the development of more efficient ternary OSCs with better controlled morphology.
关键词： sequential layer-by-layer deposition,non-fullerene acceptor,ternary organic solar cell,high performance,morphology control
更新于2025-09-23 15:19:57
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Scaled conductance quantization unravels the switching mechanism in organic ternary resistive memories
摘要： Organic ternary resistive random access memories (RRAMs) can dramatically increase information density, but the effective device yield remains too low for practical applications. Further improvements are inefficient as the switching mechanism is poorly understood. Here, we demonstrate for the first time that quantized conduction occurs and is involved in the switching mechanism of organic ternary RRAMs. The conductance values in organic ternary RRAMs are quantified in units of the quantum conductance G0 but scaled by a factor b, in contrast to that of inorganic RRAMs without scaling. In situ elemental mapping reveals that evaporated Al diffuses into organic layers and causes the formation of quantum channels. The organic materials act as diodes to regulate the external voltage and contribute to b { 1. A roughly positive correlation between the scale factor b and ternary device yield was found, which might provide a new way to improve the ternary device yield and will stimulate more material innovation for organic ternary RRAMs.
关键词： switching mechanism,organic ternary resistive random access memories,quantum conductance,quantized conduction,Al diffusion
更新于2025-09-23 15:19:57
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Performance enhancement of conjugated polymer-small molecule-non fullerene ternary organic solar cells by tuning recombination kinetics and molecular ordering
摘要： We present our study of conjugated polymer-small molecule (SM)-non-fullerene ternary organic solar cells (OSCs), which employs conjugated polymer PTB7-Th and small molecule p-DTS(FBTTh2)2 as donors and non-fullerene molecule IEICO-4F as an acceptor. It is observed that the power conversion efficiency (PCE) of ～10.9% for PTB7-Th: p-DTS(FBTTh2)2: IEICO-4F ternary OSCs with 15 wt% of p-DTS(FBTTh2)2 SM is higher than PCE of ～9.8% for PTB7-Th: IEICO-4F OSCs. Morphological studies confirm that the addition of p-DTS(FBTTh2)2 SM in PTB7-Th: IEICO-4F binary blend improves molecular ordering and crystallinity of PTB7-Th due to the favorable interaction with p-DTS(FBTTh2)2 thereby providing 3-D textured structures consisting of a mixture of edge-on and face-on orientations. The improved molecular ordering is shown to enhance exciton generation rate, exciton dissociation, charge collection, and to reduce charge recombination, all of which boosts the PCE.
关键词： PTB7-Th,Ternary,p-DTS(FBTTh2)2,IEICO-4F,GIWAXS,Non-fullerene
更新于2025-09-23 15:19:57
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On the use of multiple stacked active layers in organic photovoltaic cells
摘要： In the field of organic photovoltaic cells (OPVs), ternary planar heterojunction allows widening absorption range. Optimization of the energy levels at the organic interfaces is the first task to achieve in order to obtain OPVs with high efficiency. In ternary OPVs, carrier mobility, charge transfer and presence of energy transfer are determinant. Here, we compare the performances of different, binary (electron donor/fullerene) and ternary (electron donor/ambipolar material/fullerene) combinations of small organic molecules in planar heterojunction (PHJ) cells. We chose the different ED molecules in order to investigate the different possible band scheme alignments. The study shows that if the open circuit voltage (Voc) is limited by the energy levels of the outer layers, i.e. the difference between the lowest unoccupied molecular orbital (LUMO) of the electron acceptor and the highest occupied molecular orbital (HOMO) of the outer electron donor layer, the energy loss can be smaller than 0.2 eV. If efficient ternary OPVs need global energy offset higher than the exciton energy to separate the charges of the exciton, the distribution of this offset between DLUMO and DHOMO is not critical. The mobility value of the carriers in the intercalated layer is determinant in obtaining performance of OPVs. Overlap between the photoluminescence of ED and the optical absorption of EDA is primordial for good energy transfer. The highest OPV efficiency improvement is obtained with organic materials such as ED and EDA that have the same HOMO and similar hole mobility which give homogeneous thin layers.
关键词： organic photovoltaic cells,energy levels,energy transfer,carrier mobility,charge transfer,ternary planar heterojunction
更新于2025-09-23 15:19:57
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Non-halogenated solvent-processed ternary-blend solar cells via alkyl-side-chain engineering of a non-fullerene acceptor and its application in large-area devices
摘要： A novel asymmetric non-fullerene acceptor (T2-OEHRH) with a simple chemical structure is designed and synthesized. Compared with the symmetric T2-ORH, T2-OEHRH effectively suppresses excessive self-aggregation/crystallization and substantially improves the solubility without sacrificing photoelectrical properties. As a result, T2-OEHRH-based ternary-blend OSCs processed from a non-halogenated solvent exhibit impressive PCEs of 12.10% and 9.32% in small- and large-area devices, respectively.
关键词： non-fullerene acceptor,large-area solar cells,ternary-blend solar cells,non-halogenated solvent,asymmetric alkyl side-chain
更新于2025-09-23 15:19:57
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Introducing Trifluoromethyl to Strengthen Hydrogen Bond for High Efficiency Organic Solar Cells
摘要： Nowadays, the ternary strategy has become a common way to improve the power conversion efficiency (PCE) of organic solar cells (OSCs). The intermolecular interaction between the third component and donor or acceptor plays a key role in achieving a high performance. However, hydrogen bond as a strong intermolecular interaction is rarely considered in ternary OSCs. In this work, we introduce trifluoromethyl on a newly synthesized small molecular DTBO to strength hydrogen bonds between DTBO and IEICO-4F. Due to the existence of hydrogen bonds has a strong impact on electrostatic potential (ESP) and benefits π-π stacking in the active layer, the ternary OSCs show superior charge extraction and low charge recombination. In DTBO, PTB7-Th and IEICO-4F based ternary devices, the PCE increases from 11.02 to 12.48%, and short-circuit current density (JSC) increases from 24.94 to 26.43 mA/cm2 compared with typical binary devices. Moreover, the addition of DTBO can realize an energy transfer from DTBO to PTB7-Th and broaden the absorption spectrum of blend films. Grazing-incidence wide-angle X-ray scattering (GIWAXS) patterns show that the π-π stacking distance of IEICO-4F decreased after adding 10 wt% DTBO. The effect of the hydrogen bond is also achieved in the PM6: Y6 system, showing 16.64% efficiency by comparison to the 15.49% efficiency of binary system. This work demonstrates that introduce trifluoromethyl to enhance hydrogen bond which improve π-π stacking can achieve higher performance in OSCs.
关键词： energy transfer,ternary devices,organic solar cells,hydrogen bond,π-π stacking
更新于2025-09-23 15:19:57