Structure Of Organic Solar Cells Research Articles

A hybrid ZnO nanoparticle electron transporting layer for inverted structure organic solar cells with efficiency over 19%

A hybrid ZnO nanoparticle electron transporting layer for inverted structure organic solar cells with efficiency over 19%

A strategy for achieving high-performance single layer polymer photodetectors through dark current reduction using PMMA additives

Suppressing dark current density is crucial for optimizing the performance of organic photodetectors (PDs), particularly in terms of detectivity (D∗) and linear dynamic range (LDR). Organic PDs often utilize the bulk heterojunction structure of organic solar cells to significantly increase photocurrent. However, unlike solar cells, which are unaffected by dark current, photodetectors' performance is substantially limited by it. The interconnected network of bulk heterojunctions leads to a noticeable increase in dark current, thus degrading device performance. Typically, reducing dark current involves adding a modification layer or using multilayer planar heterojunctions, which effectively reduce dark current but often delay response speed and complicate manufacturing. This study presents an alternative approach by incorporating a small concentration of PMMA into single-layer polymer photodetectors, significantly reducing dark current without affecting photocurrent. For this single-layer polymer PD, an ultra-low dark current density of 1.25 × 10−8 A/cm2, a high Dsh∗ of 2.74 × 1012 Jones, an LDR of 120.5 dB, and a fast response time with 1.6 μs were achieved. The capacitance-voltage (C-V), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and atomic force microscopy (AFM) measurements revealed that the PMMA additive reduces internal defects, increases bulk resistance, optimizes phase separation, and enhances carrier transport efficiency. The improved device performances are attributed to a more efficient vertical arrangement of the donor-acceptor interface and carrier channels, thus reducing carrier recombination loss. These findings offer a new direction for fabricating high-performance single-layer photodetectors.

2D g-C3N5 p-Doping of Donor Material for High-Efficiency Organic Solar Cells.

Molecular doping of organic semiconductor is a great strategy for significantly regulating the electronic band structure of organic semiconductor while increasing charge mobility and carrier concentration. Here, a facile strategy is presented by introducing 2D g-C3N5 as a p-dopant into PM6, improving the charge mobility and hole carrier concentration of PM6. Moreover, the electron transfer between PM6 and g-C3N5 can effectively downshift the Fermi energy level and highest occupied molecular orbital (HOMO) energy level of PM6, which leads to the increase the built-in electric field of organic solar cells (OSCs). The addition of g-C3N5 also effectively enhances the crystallization of active layer, thereby improving the stability of OSCs. As a result, a champion bulk-heterojunction (BHJ) and layer-by-layer (LbL) structure OSCs are successfully achieved featuring a high-power conversion efficiency of 18.10%/18.25%, simultaneously having excellent device stability. This work shows that introducing a low concentration dopant into organic donor is an effective method for improving the electrical performance of organic donor and the efficiency of OSCs.

Maximizing light absorption and photocurrent in organic solar cells by aligning intrinsic absorption peaks with Fabry-Perot resonances

We provide a physical interpretation of the mechanism by which maximum light absorption is achieved in organic solar cells (OSCs) through the tailoring of Fabry-Perot (FP) resonances. Overlapping the intrinsic absorption peaks of the active layer with the FP resonances in a planar OSC structure maximizes light absorption, leading to the highest short-circuit current density (JSC). The OSC with a 119 nm-thick active layer of PTB7-Th:IEICO-4F, where intrinsic absorption peaks occur at wavelengths of 715 nm and 885 nm, exhibits fundamental FP resonant modes at wavelengths of 500, 715, 750, and 850 nm. The strong electric field intensity generated by the FP resonance coincides with the intrinsic absorption peaks of the active layer at 715 nm and 885 nm, leading to an experimentally observed JSC of 26.50 mA/cm2. Optical admittance analyses are conducted to investigate the reduced reflection associated with enhanced light absorption. These results provide a deeper understanding of the fundamental mechanism for designing multilayer photonic and optoelectronic devices. This design principle is general and can be applied to various optoelectronic devices, such as photovoltaics, sensors, and photodetectors across a wide range of wavelengths.

Sequentially Processed Bulk-Heterojunction-Buried Structure for Efficient Organic Solar Cells with 500nm Thickness.

Large-area printing fabrication is a distinctive feature of organic solar cells (OSCs). However, the advance of upscalable fabrication is challenged by the thickness of organic active layers considering the importance of both exciton dissociation and charge collection. In this work, a bulk-heterojunction-buried (buried-BHJ) structure is introduced by sequential deposition to realize efficient exciton dissociation and charge collection, thereby contributing to efficient OSCs with 500nm thick active layers. The buried-BHJ distributes donor and acceptor phases in the vertical direction as charge transport channels, while numerous BHJ interfaces are buried in each phase to facilitate exciton dissociation simultaneously. It is found that buried-BHJ configurations possess efficient exciton dissociation and rapid charge transport, resulting in reduced recombination losses. In comparison with traditional structures, the buried-BHJ structure displays a decent tolerance to film thickness. In particular, a power conversion efficiency of 16.0% is achieved with active layers at a thickness of 500nm. To the best of the authors' knowledge, this represents the champion efficiency of thick film OSCs.

Cost-effective polymer donors with simple structure for organic solar cells

This review summarized recent advances in cost-effective polymer donors with a simple structure for organic solar cells.

Gold nanostructures/quantum dots for the enhanced efficiency of organic solar cells.

Incorporating gold nanoparticles (AuNPs) into organic solar cell (OSC) structures provides an effective means to manipulate light-matter interactions. AuNPs have been used as plasmonic-enhancement and light-trapping materials in OSCs and exhibit diverse single and mixed morphologies. Substantial near-field enhancement from metal periodic structures has consistently demonstrated high enhancement in solar cell efficiency. Additionally, coupling with atomic gold clusters in the form of gold quantum dots holds promise for light harvesting through fluorescence phenomena. The configured devices optimize light utilization in OSCs by considering factors such as the morphology, position, and hybridization of localized surface plasmon resonance, propagating surface plasmon resonance, and fluorescence phenomena. This optimization enhances light absorption, scattering, and efficient trapping facilitated by gold nanostructures/quantum dots. The configured setup exhibits multiple effects, concurrently improving plasmonic and fluorescence responses under solar irradiation, thereby enhancing energy conversion performance. Integrating plasmonic nanostructures with OSCs can address fundamental issues, providing opportunities to enhance the light-absorption intensity and charge transfer efficiency at intra and intermolecular levels. This comprehensive review demonstrates that the greatest improvement in solar cell efficiency exceeded 30% compared with the reference cells.

Enhancing the Efficiency of PM6:Y6 Bulk-Heterojunction Organic Solar Cells through SCAPS Simulation Optimization

Organic solar cell (OSC) is becoming a point of attraction in the solar cell industry due to their benefits, such as light weight, flexibility, low cost, semi-transparency, and easy fabricating methods. By replacing fullerene with non-fullerene acceptors like Y6, ITIC, PCBM, and ICBA, the power conversion efficiency (PCE) of OSCs has surpassed the 15% benchmark. Here, the proposed OSC structure includes an ITO front contact electrode, SnO2 electron transport layer (ETL), PM6:Y6 active layer, Cu2O hole transport layer (HTL), and Ag back contact electrode. Systematic numerical simulation of the above proposed OSC has been performed using a solar cell capacitance simulator (SCAPS)-1D (Version 3.3.09). The device improvement analysis has been carried out in steps by analyzing the ETL-HTL effect, selecting the optimum thickness of the active layer, and the optimum value of defect density. In the first step, a PCE of 24.60% was achieved, followed by an improvement to 27.55% with the optimized defect density value. The best PCE of 27.74% was achieved in the third step with an optimized active layer thickness, leading to high fill factor (80.56%), open-circuit voltage (0.9461 V), and short-circuit current density (36.188 mA/cm2). These simulated results promote an in-depth understanding of the optical and electronic properties of PM6:Y6 blend-based OSC and show the potential of NFA-BHJ OSCs as promising candidates for solar cells in the near future.

Influence of altered parasitic aspects on the device structure for efficient organic solar cells

Influence of altered parasitic aspects on the device structure for efficient organic solar cells

Efficient and stable inverted structure organic solar cells utilizing surface-modified SnO2 as the electron transport layer

Organic solar cells (OSCs) with an inverted structure have the potential to exhibit both high efficiency and stability, in which the electron transport layer (ETL) plays a crucial role. In this study, we have developed an efficient ETL for inverted structure OSCs by modifying commercially available SnO2 nanoparticles with a simple molecule 2-(3-(dimethylamino)propyl)− 1,3-dioxo-2,3-dihydro-1 H-benzo[de]isoquinoline-6,7-dicarboxylic acid (NMA). The surface modification effectively eliminates the light soaking issue observed in devices with bare SnO2. Furthermore, it significantly enhances the efficiency and stability of the photovoltaic devices. With the hybrid ETL, the device based on PM6:L8-BO achieves an outstanding power conversion efficiency (PCE) of 18.33 %. Notably, the champion device exhibits excellent shelf, thermal and photo stabilities. It maintained 99.7 % and 87.1 % of its original efficiency under storage in N2 and thermal stress at 65 ℃ for 1000 h, respectively. Under continuous 1-sun illumination with maximum power point tracking for 800 h, the device retained 86.6 % of its initial efficiency. Additionally, the hybrid ETL shows good generality on other typical active layer systems based-OSCs. This work presents an effective hybrid ETL approach for the development of high-performance OSCs.

Benzotriazole-based asymmetric nonfullerene acceptors with A-D-A1-A2 type structure for organic solar cells

Although the wide-bandgap benzotriazole (BTA)-based A2-A1-D-A1-A2 type nonfullerene acceptors (NFAs) have realized super-high open-circuit voltage (VOC) of 1.3 V, the short-circuit current density (JSC) of these materials lag behind the narrow-bandgap A-D-A type analogs. Here, we design and synthesize two asymmetric A-D-A1-A2 type molecules, A301 and A302, by adopting 1,1-dicyanomethylene-3-indanone (IC), BTA and 2-(1,1-dicyanomethylene)rhodanine (RCN) as A, A1 and A2 units, respectively. Under the synergistic regulation of asymmetric end groups and side chain engineering, A302 with alkyl side chains on D unit exhibits red-shifted absorption, tighter molecular packing, and stronger crystallinity in comparison with A301 with phenyl side chain. Consequently, PM6:A302-based organic solar cells (OSCs) realize an enhanced efficiency of 11.09% with an improved JSC of 17.95 mA cm−2, compared to those of PM6:A301-based device (PCE = 8.18%, JSC = 14.57 mA cm−2). Notably, the JSC of 17.95 mA cm−2 is the highest value for BTA-based NFAs to date. This work demonstrates A-D-A1-A2 type NFAs have great potential to balance the JSC and VOC, and side chain on D unit also has a great impact on the properties of this kind of materials.

Self‐Doping of the Transport Layers Decreases the Bimolecular Recombination by Reducing Static Disorder

Electron‐transport layers (ETLs) have a crucial role in the solar cells’ performance. Generally, ETLs are characterized in terms of the interface properties and conductivity rather than their effect on the photoactive layer. Herein, two ETLs, 2,9‐bis(3‐((3‐(dimethylamino)propyl)amino)propyl)anthra[2,1,9‐def:6,5,10‐d′e′f′]diisoquinoline‐1,3,8,10(2H,9H)‐tetraone (PDINN) and 2,9‐bis[3‐(dimethyloxidoamino)propyl]anthra[2,1,9‐def:6,5,10‐d′e′f′]diisoquinoline‐1,3,8,10(2H,9H)‐tetrone, are compared in the conventional PM6:Y6 organic solar cell (OSC) structure and the influence of the ETL on the photoactive layer is shown. It is shown that a significant portion of the unpaired electrons of PDINN is mobile by combining electron paramagnetic resonance and Hall effect measurements. It is established that the high doping in PDINN ETL changes the dark electron concentration of the photoactive layer. The impacts of this change in the photoactive layer can be observed in the reduced static energetic disorder, and subsequently in the (nonradiative) recombination of free carriers. The results can be used to suppress nonradiative recombination in OSC, which can significantly boost their efficiency.

The impact of the buffer layer material and active layer thickness on the performance of a fullerene-free organic solar cell

This paper presents a step-by-step study of an organic solar cell structure by simulation. The study focuses mainly on the effect of buffer layer material on the performance of a fullerene-free organic solar cell. The studied structure composed of PBDB-T: ITIC polymer donor/small molecule acceptor blend active layer, was selected based on its considerably good power conversion efficiency compared to its peers, it has been proven that the small molecular compound ITIC performed better than the fullerene PC71BM. [1] Compared to available experimental data of the studied structure, simulation results showed an error of 2.05%, and based on that, starting from a power conversion efficiency of 11.44% we continued our study by varying buffer layer materials, and thicknesses of the active layer and interlayers thus achieving an efficiency of 12.25%.

The role of a highly optimized approach with superior transparent conductive oxide anode towards efficient organic solar cell

The effort emphasizes the numerical analysis of different transparent conducting oxides (TCOs) perspectives, which include ITO, FTO, AZO, and IZO anode-based organic solar cells (OSCs) with the drift-diffusion approach. The prior selection of aluminum-doped zinc oxide (AZO) as TCO is feasible for more extended transparency and antireflection due to a tailored absorption wavelength of <380 nm and the factors of higher mechanical flexibility, low-cost processing, and realistic performance at lower temperatures. To confirm the stability and reproducibility of the design OSC, the contribution of each interfacial layer thickness, i.e., AZO as TCOs, P3HT: PC61BM as an organic absorbing layer (OAL), Spiro-OMeTAD (SOT) as a hole-transport layer (HTL), and ZnO as an electron-transport layer (ETL), is also investigated. Furthermore, functions of optimum trap-state densities () and charge carrier mobility () in OAL have been performed to aid in increasing the diffusion length of excitons carriers (). These properties led to better photogeneration and transport of charge carriers, decreasing the series resistance (RS), leading to lower bimolecular recombination, a long carrier lifetime (), and consequently higher power conversion efficiency (PCE). The findings revealed that the proposed OSC structure achieves an excellent PCE of 10.28% for AZO as TCO with an 850 nm ultra-thick OAL under AM 1.5 G light irradiation. Hence, a better fabrication process for efficient OSC could also be improved by the optimization of all these critical factors for future research.

Improving the Efficiency of Organic Solar Cells via the Molecular Engineering of Simple Fused Non-Fullerene Acceptors

The development of novel non-fullerene small-molecule acceptors (NFAs) with a simple chemical structure for high-performance organic solar cells (OSCs) remains an urgent research challenge to enable their upscaling and commercialization. In this work, we report on the synthesis and comprehensive investigation of two new acceptor molecules (BTPT-OD and BTPT-4F-OD), which have one of the simplest fused structures among the Y series of NFAs, along with the medium energy bandgap (1.85 eV–1.94 eV) and strong absorption in the visible and near-IR spectral range (700–950 nm). The novel NFAs have high thermal stability, good solubility combined with a high degree of crystallinity, and deep-lying levels of the lowest unoccupied molecular orbital (up to −3.94 eV). The BTPT-OD with indan-1-one-3-dicyanvinyl terminal acceptor group is superior to its counterpart BTPT-4F-OD with 5,6-difluorindan-1-one-3-dicyanvinyl group both in the number of synthetic steps and in the photovoltaic performance in OSCs. PM6:BTPT-OD systems exhibit superior photovoltaic performance due to the higher charge mobility and degree of photoresponsiveness, faster carrier extraction, and longer carrier lifetime. As a result, BTPT-OD has almost two times higher photovoltaic performance with PM6 as a donor material due to the higher JSC and FF than BTPT-4F-OD systems. The results obtained indicate that further development of OSCs can be well achieved through a rational molecular design.

Unconventional organic solar cell structure based on hyperbolic metamaterial

An unconventional organic solar cell structure based on hyperbolic metamaterials (HMMs) was designed, fabricated, and demonstrated with improved performance for the first time.

Enhanced Optical Confinement Enriching the Power Conversion Efficiency of Integrated 3D Grating Organic Solar Cell.

In this paper, we examine the impact of three-dimensional grating layers embedded at selected locations in an organic solar cell structure to obtain enhanced efficiency. The design, simulations, and optimizations were carried out using an in-house tool based on the rigorous coupled-wave analysis (RCWA) method developed on the MATLAB R2019a platform. An optimal organic solar cell structure design with a top grating layer exhibited an increase of in the short-circuit current density compared to an organic solar cell structure with a smooth top layer. The power conversion efficiency (PCE) increase was mainly due to increased light confinement in the thin absorbing layer. Adding an embedded grating layer in the absorption layer resulted in a significant increase in the absorptance spectral bandwidth, where the short-circuit current density increased by . In addition, the grating cells yielded a substantial improvement in the cell’s conical absorptance since the existence of a surface plasmon polariton (SPP) in the back metal gratings increases the confinement properties. Further, the effect of a pyramid-shaped embedded grating array was a slight improvement in the PCE compared to the rectangular-shaped grating arrays. We showed that a pyramid-grating can act as a nano black-body layer, increasing the absorption for a wide range of azimuthal and polar incident angles.

High-efficiency ternary sequential solution deposition structure organic solar cells with two polymer donors

Ternary organic solar cells (OSCs) as a promising device can simultaneously improve photovoltaic parameters compared with traditional binary OSCs. However, efficient ternary OSCs with two polymer donors are rarely reported due to the highly conformational freedom and incompatibility. Herein, the influences of device processing on ternary device performance were systematically studied with wide bandgap polymer donor PBB-TSD incorporated into PM6:Y6 system. The optimized traditional ternary bulk heterojunction (BHJ) OSCs achieved a PCE of 17.40%. Interestingly, the ternary sequential solution deposition (SSD) structure OSCs can effectively avoid the enrichment of acceptors at the anode and reduce the recombination. Hence, the ternary SSD structure OSC recorded a further improved PCE of 17.71%, especially compared with BHJ structure OSC (16.30%). Meanwhile, the ternary SSD structure strategy has also been applied to PM6:BTP-eC9 system with improved PCE of 18.14%. This work not only shows the potential of guest polymer donors in complementary light absorption of shortwave length range, but also reveals a simple but effective approach for boosting efficient ternary OSCs with two polymer donors.

Development of non-fused acceptor materials with 3D-Interpenetrated structure for stable and efficient organic solar cells

The modification of end-capped acceptors of a molecule is an efficient strategy for novel solar cells. In this line, we have tailored and explored eight novel molecules for possible application in photovoltaics. Further, a neat and clean light absorption spectrum has been recorded for designed molecules (T1-T8) in the organic solvent. The lower values of excitation energy of novel molecules help in easy excitation and dissociation of excitation in the excited state. Moreover, the mobility in the active layer of electron and hole of solar cell is high, which is seen in T1 to T8 molecules. Overall, the geometric and physiochemical analysis highlights the high performance of tailored molecules of solar cells. The density functional theory (DFT) calculations were used to estimate FMO analysis, Electrostatic-Potential (ESP), Density of States (DOS) graphs, Reorganizational Energy, photovoltaic properties, and charge transmission investigation. Engineered particles have greater and identical optoelectronic properties than synthetic reference molecules. T5 has emerged as the best candidate among all the molecules studied because of its talented photovoltaic properties, which contain the minimum bandgap (1.99 eV), the mobility of electrons, and hole are (λe = 0.0112 eV), (λh = 0.0101 eV), respectively. These materials showed a lower binding energy (Eb = 0.48 eV), and are highly red-shifted in absorption spectrum i.e. 798.55 nm (in gas), while 820.49 nm in chloroform. Moreover, these materials also presented a good value of Open circuit voltage (Voc), which are in the range of 1.26–1.83 V for the designed series (T1-T8), while 1.77 V for the R molecule. Therefore, we highly suggest these materials for the future development of an efficient organic solar cells (OSCs).

Fundamentals of organic solar cells: A review on mobility issues and measurement methods

In the past few years, there have been impressive breakthroughs to enhance the structure of organic solar cells (OSCs) in order to improve the performance. Resulting in increment of the power conversion efficiency (PCE) from 5% to 18% in OSCs and up to 25% in OSCs module. The Developments cause these thin and flexible, eco-friendly, and low-cost photovoltaic devices to be promising technology for wide range of applications such as internet of things (IOT), sensors, architecture, and wearable electronics.In the past few years, there have been impressive breakthroughs to enhance the structure of organic solar cells (OSCs) in order to improve the performance. Resulting in increment of the power conversion efficiency (PCE) from 5% to 18% in OSCs and up to 25% in OSCs module. The Developments cause these thin and flexible, eco-friendly, and low-cost photovoltaic devices to be promising technology for wide range of applications such as internet of things (IOT), sensors, architecture, and wearable electronics. Further, in this article, fundamental characteristics, operation principles, charge carriers transport mechanisms, and electrical model parameters of an OSC is reviewed. Considering polymers as main and most common building blocks of an OSC, charge transport and current models also have been studied. In addition, mobility characteristics, as one of the critical parameters affecting the OSC performance has investigated. Time of flight (TOF), space charge limited current (SCLC), charge extraction by linearly extracting voltage (CELIV), and impedance spectroscopy as the four fundamental methods to measure mobility in OSCs along with discussion about the advantages and drawbacks of each technique have been studied.