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Elongated Nanodomains and Molecular Intermixing Induced Doping in Organic Photovoltaic Active Layers with Electric Field Treatment
摘要： The effects of the electric-field-assisted annealing on the bulk heterojunction nano-morphology in the P3HT/PCBM active layer of the organic photovoltaic cells (OPVCs) are presented here. It was widely accepted that the electric-field-assisted annealing will facilitate the P3HT, the polar polymer, to be better crystalline to enhance the charge mobility, hence the improvement of the OPVC performance. The influences on the nano-morphology of the electron donor and accepter domains are not well understood. Here, using the cross-sectional scanning tunneling microscopy and spectroscopy (XSTM/S), the electric-field-assisted annealing treatment is found to influence the molecular domains to be elongated along the direction of the external electric field. The elongation of the molecular domains is believed to facilitate the domain percolation, which causes higher charge mobility, hence the higher short-circuit current density (Jsc). On the other hand, it was also observed that the electronic properties of the P3HT-rich and PCBM-rich domains in the electric-field-assisted annealed samples showed smaller energy band gaps and smaller molecular orbital offset between the two domains, which is believed to decrease the open circuit voltage (Voc) and negatively impact the OPVC performance. Based on the X-ray diffraction (XRD) and small angle X-ray scattering (SAXS) results, the altered electronic properties are argued to be due to the molecular intermixing induced doping effects. These results point out competing factors affecting the OPVC performance with the electric-field-assisted annealing treatment.
关键词： Bulk heterojunction,Cross-sectional scanning tunneling microscopy,Organic Solar Cells,X-ray Diffraction,Small Angle X-ray Scattering,Nanomorphology
更新于2025-09-12 10:27:22
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Photovoltaic effect in bulk heterojunction system with glass forming indandione derivative DMABI-6Ph
摘要： The aim of the work is to evaluate possible use of 2-[[4-(bis(2-trityloxyethyl)amino)phenyl]methylene]indane-1,3-dione (DMABI-6Ph) as light absorbing material for solar cells. DMABI-6Ph is a perspective material due to its good photoelectrical, thermal and chemical properties. The main advantage of DMABI-6Ph is its ability to form amorphous films by wet-casting methods thus allowing using the compound in organic solar cells made from solution. For now most popular materials for solution processable solar cells are polymer P3HT and fullerene derivative PCBM, but lot of investigations are in the field of new low molecular weight materials to replace the polymer. Photoelectrical measurements were made to determine molecule ionization and electron affinity levels of DMABI-6Ph. Difference of 2.06 eV between DMABI-6Ph ionization level and PCBM affinity level was obtained. Accordingly open circuit voltage of system DMABI-6Ph:PCBM was measured up to 0.78 V. The best power conversation efficiency was 0.11 % for the DMABI-6Ph:PCBM mass fraction 2:1. Limiting factor for high efficiency could be low charge carrier mobility which can be increase by additional DMABI-6Ph modification.
关键词： energy levels,glass forming structure,bulk heterojunction,indandione group,power conversion efficiency
更新于2025-09-12 10:27:22
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[IEEE 2019 34th Symposium on Microelectronics Technology and Devices (SBMicro) - Sao Paulo, Brazil (2019.8.26-2019.8.30)] 2019 34th Symposium on Microelectronics Technology and Devices (SBMicro) - Electrical characterization of bulk heterojunction organic solar cells using PAni:PSS Layer-by-Layer films
摘要： Herein we report the evaluation of a PAni:PSS Layer-by-Layer (LbL) ultrathin film as hole transport layer (HTL) of Bulk Heterojunction Organic Solar Cells (OSC). It was also highlighted the importance of using a lithium fluorite (LiF) dielectric layer to improve devices overall performance. The best result was found for devices comprising five PAni:PSS bilayers and a LiF dielectric layer in a thin film structure. There is a perspective of increasing device’s efficiency based on LbL materials used as HTL and their deposition parameters.
关键词： polyaniline,bulk heterojunction organic solar cells,Layer-by-layer technique,organic solar cells electrical characterization
更新于2025-09-12 10:27:22
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High detectivity organic photodetectors in the visible light wavelength with ternary bulk heterojunction
摘要： In this work, we report an ternary bulk heterojunction (t-BHJ) organic photodetectors (OPDs) based on P3HT, PTB7 and PC61BM. The effects of PTB7 added to P3HT:PC61BM on the optical and electrical properties of OPDs were investigated. It is found that when the mass ratio of P3HT:PTB7:PC61BM is 8:2:10, the response spectrum of the active layer is extended to 780 nm, The responsivity (R) and external quantum efficiency (EQE) of the OPDs are reached 178, 291, 241 mA/W and 35%, 68%, 65%, under 630, 530, and 460 nm illumination and ?1 V bias, respectively, and the detectivity (D*) reached 1012 Jones. The results show that the addition of PTB7 with appropriate mass ratio can increases the exciton generation and dissociation probability in P3HT:PC61BM, which increases the photocurrent of the device. In addition, the addition of PTB7 promotes the crystallization of the film, reduces the density of trap defects in the film, and reduces the dark current of the device.
关键词： Microscopic morphology,Organic photodetectors,Ternary bulk heterojunction,Exciton dissociation
更新于2025-09-12 10:27:22
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Role of Platinum Octaethylporphyrin(PtOEP) in PCPDTBT: PCBM solar cell performance
摘要： Bulk heterojunction polymer solar cells based on poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b’]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole) [6,6]:- Phenyl-C61 butyrie acid methyl ester (PCPDTBT: PCBM) blends were doped by different amount(0,0.5,1,2,3 and 6 mg) from Platinum Octaethylporphyrin(PtOEP). The effect of PtOEP on the surface morphology, Raman spectra, optical absorbance, and photovoltaic properties was studied. We found that the best performance for PCPDTBT: PCBM device with 33.5% enhancement in power conversion ef?ciency was achieved when we added 1 mg from PtOEP. The impedance spectroscopy was examined in the frequency range from 0.025 to 1000 KHz. The equivalent circuit model was analyzed in detail to evaluate the interface and recombination processes. The highest diffusion coef?cient and mobility were found for PCPDTBT: PCBM: PtOEP(1 mg)device, which records a more ef?cient exciton dissociation at the interface and a faster charge transport processes.
关键词： PCPDTBT,PtOEP,Impedance spectroscopy,Bulk heterojunction (BHJ),PCBM
更新于2025-09-12 10:27:22
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Influence of single-walled carbon nanotubes induced exciton dissociation improvement on hybrid organic photovoltaic devices
摘要： Torch-plasma-grown single-walled carbon nanotubes (SWCNTs) are integrated with regioregular poly(3-hexylthiophene) (P3HT) and a fullerene derivative 1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C61 (PCBM) as a hybrid photoactive layer for bulk heterojunction solar cell devices. We demonstrate that molecular information could be accurately obtained by time-of-flight secondary ion mass spectrometry through the hybrid organic photoactive solar cell layers when sputtering is performed using a Cs+ 2000 eV ion source. Furthermore, the photovoltaic (PV) performance of the fabricated devices show an increase in the short-circuit current density (Jsc) and the fill factor (FF) as compared to the pristine devices fabricated without SWCNTs. The best results are obtained with 0.5 wt. % SWCNT loads, where an open-circuit voltage (VOC) of 660 mV is achieved, with a Jsc of 9.95 mA cm?2 and a FF of 54%, leading to a power conversion efficiency of 3.54% (measured at standard test conditions, AM1.5 g). At this optimum SWCNT concentration of 0.5 wt. %, and to further understand the charge-transfer mechanisms taking place at the interfaces of P3HT:PCBM:SWCNT, Jsc is measured with respect to the light intensity and shows a linear dependency (in the double logarithmic scale), which implies that losses in the charge carrier are rather governed by monomolecular recombination. Finally, our results show that our hybrid devices benefit from the fullerene electron accepting nature and from the SWCNT fast electron transportation feature that improve substantially the exciton dissociation efficiency. The influence of the SWCNTs on the Fermi level and the work function of the photoactive composite and its impact on the PV performance is also investigated.
关键词： single-walled carbon nanotubes,bulk heterojunction,PCBM,hybrid organic photovoltaic devices,photovoltaic performance,P3HT,exciton dissociation
更新于2025-09-12 10:27:22
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Side chain effect on conjugated polymer/fullerene interfaces in organic solar cells: a DFT study
摘要： Considerable experimental research has been conducted on the influence of polymer alkyl side chains on the performance of bulk heterojunction organic solar cells. However, greater insight into the role of alkyl side chains in the polymer/fullerene interfacial regions is still needed. Using the dispersion-corrected density functional theory, we investigate the effect of alkyl side chains on the binding energies and electronic structures of various molecular pairings of fullerenes and monomers of organic copolymers (e.g. a pair of PC71BM and a monomer of copolymer PTB7 based on the thieno[3,4-b]thiophene/benzodithiophene repeat unit, PCBM and a copolymer PCDTBT based on 2,7-carbazole/dithienyl-2,1,3-benzothiazole and PC71BM and a copolymer PffBT4T-2OD based on difluorobenzothiadiazole/quaterthiophene). We find that the trends of the magnitudes of the binding energies vary with the lengths, types (branched or linear), and branching positions of alkyl side chains. Whenever possible, these results are compared with the efficiency trends of the corresponding organic solar cells. With the help of this comparison optimal side chain arrangements in bulk heterogeneous organic solar cells are identified. It is expected that these insights will aid in the production of more efficient organic photovoltaics.
关键词： binding energies,polymer alkyl side chains,organic solar cells,dispersion-corrected density functional theory,bulk heterojunction,electronic structures
更新于2025-09-12 10:27:22
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Effect of PVP-Capped ZnO Nanoparticles with Enhanced Charge Transport on the Performance of P3HT/PCBM Polymer Solar Cells
摘要： We attempted surface modification in ZnO nanoparticles (NPs) synthesized by the sol–gel process with polyvinyl pyrrolidone (PVP) applied to bulk-heterojunction polymer solar cells (PSCs) as an electron transport layer (ETL). In general, ZnO NPs have trap sites due to oxygen vacancies which capture electrons and degrade the performance of the PSCs. Devices with six different PVP:Zn ratios (0.615 g, 1.230 g, 1.846 g, 2.460 g, 3.075 g, and 3.690 g) were fabricated for surface modification, and the optimized PVP:Zn ratio (2.460 g) was found for PSCs based on P3HT/PCBM. The power conversion efficiency (PCE) of the fabricated PSCs with PVP-capped ZnO exhibited a significant increase of approximately 21% in PCE and excellent air-stability as compared with the uncapped ZnO-based PSCs.
关键词： ZnO,polymer solar cells,PVP,surface modulation,oxygen,bulk-heterojunction,polyvinyl pyrrolidone
更新于2025-09-12 10:27:22
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Regulating the Phase Separation of Ternary Organic Solar Cells via 3D Architectured AIE Molecules
摘要： An optimized bulk heterojunction (BHJ) interface, certifying enhanced exciton-splitting, charge separation and recombination inhibition, is vastly desired to obtain high power conversion efficiencies (PCEs). Herein, the ternary strategy has been employed to effectively modify the phase separation between the J71:ITIC blend by incorporating a 3D aggregation-induced emission (AIE) material, Tetraphenylethylene (TPE). Hence, as a consequence of improved charge mobility, lower bimolecular recombination and enhanced fill factor (FF), an excellent PCE of 12.16% has been achieved; a 21.23% increment over the PCE of binary devices. Likewise, Flory-Huggins parameter (c ) and surface free energy analysis reveals a high degree of miscibility between J71 and TPE, that leads to a rearrangement at the D-A interface such that TPE settles in between the D and A and thus forces the ITIC away from J71 and out of the mixed phase, indicating relatively higher average acceptor domain purity at the interface and ultimately better FF and PCE for the ternary devices. Likewise, TPE inclusion in various other fullerene and nonfullerene systems also leads to similar results, signifying this to be an effective methodology to boost the PCEs of the organic solar cells, especially for the systems with low FF.
关键词： energy transfer,aggregation-induced emission,3D molecule,ternary organic solar cells,bulk heterojunction interface,phase separation
更新于2025-09-12 10:27:22
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Impact of Donor–Acceptor Interaction and Solvent Additive on the Vertical Composition Distribution of Bulk-Heterojunction Polymer Solar Cells
摘要： The vertical composition distribution of bulk-heterojunction (BHJ) photoactive layer is known to have dramatic effects on photovoltaic performance in polymer solar cells. However, the vertical composition distribution evolution rules of BHJ films are still elusive. In this contribution, three BHJ film systems, composed of polymer donor PBDB-T and three different classes of acceptor –fullerene acceptor PCBM, small molecule acceptor ITIC, and polymer acceptor N2200 –are systematically investigated using neutron reflectometry to examine how donor–acceptor interaction and solvent additive impact the vertical composition distribution. Our results show that those three BHJ films possess homogeneous vertical composition distributions across the bulk of the film. While very different composition accumulations near the top and bottom surface were observed which could be attributed to different repulsion, miscibility, and phase separation between the donor and acceptor components as approved by the measurement of donor–acceptor Flory–Huggins interaction parameter χ. Moreover, the solvent additive 1,8-diiodooctane (DIO) can induce more distinct vertical composition distribution especially in non-fullerene acceptor based BHJ films. Thus, higher power conversion efficiencies were achieved in inverted solar cells because of facilitated charge transport in active layer, improved carrier collection at electrodes, suppressed charge recombination in BHJ solar cells.
关键词： Flory–Huggins Interaction Parameter χ,Bulk-Heterojunction,Neutron Reflectometry,Polymer Solar Cells,Vertical Composition Distribution
更新于2025-09-12 10:27:22