Layer Of Organic Solar Cells Research Articles

Morphology Optimization by Non-Halogenated and Twisted Volatile Solid Additive for High-Efficiency Organic Solar Cells.

Recently, volatile solid additives have attracted tremendous interest in the field of organic solar cells (OSCs), which can effectively improve device efficiency without sacrificing the reproducibility and stability of the device. However, the structure of reported solid additives is onefold and its working mechanism needs to be further investigated. Herein, a novel non-halogenated and twisted solid additive 1,4-diphenoxybenzene (DPB) is employed to optimize the morphology of the active layer in OSCs. The properties of additive DPB, morphology of active layer, and carrier dynamics behaviors have been systematically investigated through theoretical calculations, in situ and ex situ spectroscopy, grazing-incidence wide-angle X-ray scattering (GIWAXS), and grazing-incidence small-angle X-ray scattering (GISAXS) measurement, as well as ultrafast spectroscopy technology. The results reveal that the twisted additive DPB selectively interacts with acceptor Y6, and thus forms optimized morphology of active layer with increased molecular crystallinity, tight molecular packing, and favorable phase separation. As a result, the optimized devices deliver a remarkable power conversion efficiency (PCE) of 19.04%, which is the highest value for the D18-Cl:N3 system to date. These results demonstrate that non-halogenated and twisted solid additive DPB has broad prospects in the preparation of highly efficient OSCs, providing theoretical and experimental guidance for the development of high-performance solid additives.

Constructing Multiscale Fibrous Morphology to Achieve 20% Efficiency Organic Solar Cells by Mixing High and Low Molecular Weight D18.

This study underscores the significance of precisely manipulating the morphology of the active layer in organic solar cells (OSCs). By blending polymer donors of D18 with varying molecular weights, a multiscale interpenetrating fiber network structure within the active layer is successfully created. The introduction of 10% low molecular weight D18 (LW-D18) into high molecular weight D18 (HW-D18) produces MIX-D18, which exhibits an extended exciton diffusion distance and orderly molecular stacking. Devices utilizing MIX-D18 demonstrate superior electron and hole transport, improves exciton dissociation, enhances charge collection efficiency, and reduces trap-assisted recombination compared to the other two materials. Through the use of the nonfullerene acceptor L8-BO, a remarkable power conversion efficiency (PCE) of 20.0% is achieved. This methodology, which integrates the favorable attributes of high and low molecular weight polymers, opens a new avenue for enhancing the performance of OSCs.

The use of 1D carbon nanotube interacting with caffeine molecules for applications in solar cells: structure optimisation, Raman analysis and optoelectronic properties

This study proposes a promising candidate for organic solar cells through the creation of a novel nano-hybrid system composed of caffeine molecules encapsulated within a semiconducting single-walled carbon nanotube known as NT14 (14,0). The stability and optoelectronic properties of this hybrid system, designated as CA@NT14, were thoroughly investigated. We determined the optimal diameter for the NT14 nanotube using molecular mechanics, Density Functional Theory, spectral moment’s method, and bond polarizability model, finding it to be approximately 1.18 nm. The encapsulation’s impact on the Raman-active modes, specifically the radial breathing mode and tangential mode, was analyzed through Raman spectra calculations, revealing structural stability and charge transfer from CA to NT14. Notably, the NT14’s Fermi level position increased upon encapsulation, indicating charge transfer and a type-II band alignment. The study further examined the bandgap characteristics of the hybrid system, finding that the encapsulation of CA within semiconducting NT14 nanotubes minimally impacts the nanotube’s bandgap, thus retaining its excellent visible light absorption properties. Conversely, encapsulating CA within metallic nanotubes significantly reduces their bandgap, limiting their light absorption range. The nonresonant Raman responses of NT14 pre- and post-encapsulation corroborated the charge transfer between CA and NT14. Future research will focus on computing the electronic transport characteristics, transmission spectra, I-V characteristics, and yield of CA@NT14 using DFT and Non-Equilibrium Green’s Function ( formalism. An experimental study will be conducted to validate these theoretical findings. These results indicate the potential of CA@NT14 hybrids as effective active layers in organic solar cells, highlighting their significance in advancing optoelectronic applications.

Designed Polar Cosolvent-Prepared Zinc Oxide Film for Efficient and Stable Inverted Organic Solar Cells.

Here, a simple method of applying dimethylformamide (DMF) as cosolvent in the sol-gel technology is used to improve the quality of ZnO bulk films. First-principles calculations show that with the addition of polar solvent DMF, the adsorption energy (Eads) between the solvent and Zn(OH)₂ increases from -1.42 to -1.74eV, which can stabilize the existence of Zn(OH)₂, thereby promoting the ZnO synthesis. Besides, the elimination of amine residues in the DMF-ZnO film significantly suppress the photocatalytic activity induced by amine-induced coordination or redox reactions. Inverted organic solar cells (OSCs) based on PM6:Y6 and PM6:BTP-eC9 achieves impressive power conversion efficiencies (PCE) of 17.58 and 18.14%, respectively. Furthermore, benefiting from the reduced defects of bulk ZnO, pseudo-bilayer bulk heterojunction (PBHJ) devices based on the optimized ZnO film exhibited superior stability, the PM6:Y6 devices based on DMF-ZnO ETLs can maintain 90.28% of their initial PCE after 1000 h of thermal aging at 85°C, and 80.98% of their initial PCE after 168 h of UV aging. This simple solvent optimization strategy can significantly improve the charge transport of ZnO bulk films, making it a reliable strategy for the preparation of electron transport layers in OSCs.

Fine Tuning the Work Function of ZnO Cathode Buffer Layers in Organic Solar Cells by Phenanthroline Coordination

Fine Tuning the Work Function of ZnO Cathode Buffer Layers in Organic Solar Cells by Phenanthroline Coordination

Application of isoindigo-based small molecule conjugated electrolytes at interfaces with organic solar cells

Zwitterionic small molecule materials are widely employed in the cathode interface layer of organic solar cells (OSCs). Nevertheless, the exploration of superior cathode interface materials with the objective of enhancing the performance of OSCs remains a significant challenge. Two water/alcohol soluble n-type self-doped small molecule conjugated electrolytes were synthesized using isoindigo as the acceptor unit and triphenylamine (TPA) as the donor unit. Quaternary ammonium salts or pyridine salts were used as the polar side chains. When applied to organic solar cells (OSCs) with PTB7-Th: PC71BM as the active layer, the devices showed improved performance. The power conversion efficiency (PCE) reached 8.59 % (IIDN2TPA) and 8.81 % (IIDPy2TPA), respectively. These results demonstrate the water/alcohol-soluble D-A-D-type small-molecule conjugated electrolytes offer an effective strategy in designing cathode interlayer (CIL) and preparing the high-performance OSCs.

To Maximize Luminescence for an Efficient Organic Solar Cell†

Comprehensive SummaryWith the continuous development of photovoltaic materials, organic solar cells (OSCs) have made remarkable advancements, surpassing a power conversion efficiency (PCE) of 20%. However, the PCEs of OSCs remain lower than that of inorganic solar cells due to significant energy losses, mainly stemming from the relatively large non‐radiative recombination losses (usually be expressed as ∆E3), resulting in low open‐circuit voltages. This can be achieved by reducing non‐radiative recombination, and hereby increasing the electroluminescence quantum efficiency (EQEEL) of the photo‐active layer. This review analyzes the significance of luminescence efficiency in achieving high‐performance OSCs by examining the reciprocal relationship between ∆E3 and EQEEL. High‐efficiency organic solar cells can also be used as effective organic light‐emitting diodes (OLEDs). The discussion provides insights into the influencing factors of EQEEL and the mechanisms for adjusting various parameters, which include enhancements in photoluminescence quantum yield and the proportion of radiative excitons. The objective is to offer insights into the crucial role of luminescence performance in OSC development, guiding researchers toward developing novel photovoltaic materials or optimization strategies to enhance the luminescence performance of the active layer in OSCs, fostering the simultaneous advancement of OSCs and OLEDs. Key Scientists

Novel self-doping alcohol-soluble quinacridone-based small molecule at the cathode interface layer of organic solar cells

Interfacial modification plays a crucial part in improving the photovoltaic performance and stability of organic solar cells (OSCs). The self-doping effect can enhance the inter-ohmic contact at the active layer material with the cathode. Therefore, we synthesised a self-doping alcohol-soluble quinacridone-based small molecule, 5,12-bis(3-(dimethylamino)propyl)-5,12-dihydroquinolo[2,3-b]acridine-7,14-dione (QAN), with a self-doping effect, and introduced QAN as cathode interfacial layers (CILs) into OSCs. The central nuclear structure of QAN is an electron-deficient unit with a large conjugated structure. This structure facilitates electron transport as a cathode-interface material. Additionally, its polar side chains enhance the solution-processing capability and contribute to a more pronounced self-doping effect. Compared with the devices without interfacial material, the open-circuit voltage(VOC) and short-circuit current (JSC) with QAN as an interfacial material increased. What's more, the optimal photoelectric conversion efficiency (PCE) of the QAN CIL device is increased to 9.05 % for the same experimental conditions, which is 40 % higher than the device without interface material. By characterizing the surface morphology, it was found that the PTB7-Th:PC71BM active layer devices exhibited a smooth surface morphology and improved hydrophilicity when inserted with QAN CIL, which helps to enhance the physical contact of the active layer with the cathode, in addition to charge extraction and transport. This result suggests that introducing QAN as the CILs of the device is a viable way to improve the performance of the OSCs.

Polyfluoride Acceptor with Limited Molecular Diffusion Enables Efficient and Stable Ternary Organic Solar Cells.

Due to the slow diffusion of photovoltaic molecules, in particular, small-molecule acceptors (SMAs), under light and heating, the morphology of the active layer in organic solar cells (OSCs) prefers to deviate from the favorably metastable status, leading to the challenge of stability during long-term operation. Employing materials with a high glass transition temperature (Tg) as the third component to suppress molecular diffusion is an efficient method to achieve the balance of efficiency and stability of OSCs. Herein, a dimerized small-molecule acceptor denoted as F6D is synthesized by introducing a polyfluoride moiety as the linker to enhance the Tg. Benefitting from a rational molecular design, F6D not only exhibits a higher Tg, complementary absorption, and cascade energy levels with the host materials of the polymer donor PM6 and the SMA Y6 but also has excellent miscibility and multiple intermolecular interactions with Y6. As a result, a champion power conversion efficiency of 17.52% is achieved in the optimal PM6:Y6:F6D-based device. More importantly, the ternary device exhibits superior stability under continuous heating and lighting compared with the binary device.

Utilization of Polycyclic Aromatic Solid Additives for Morphology and Thermal Stability Enhancement in Photoactive Layers of Organic Solar Cells.

Volatile solid additives have emerged as a promising strategy for enhancing film morphology and promoting the power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, a series of novel polycyclic aromatic additives with analogous chemical structures, including fluorene (FL), dibenzothiophene (DBT), and dibenzofuran (DBF) derived from crude oils, are presented and incorporated into OSCs. All these additives exhibit strong interactions with the electron-deficient terminal groups of L8-BO within thebulk-heterojunction OSCs. Moreover, they demonstrate significant sublimation during thermal annealing, leading to increase free volumes for the rearrangement and recrystallization of L8-BO. This phenomenon leads to an improved film morphology and an elevated glass-transition temperature of the photoactive layers. Consequently, the PCE of the PM6:L8-BO blend has been boosted from 16.60% to 18.60% with 40 wt% DBF additives, with a champion PCE of 19.11% achieved for ternary PM6:L8-BO:BTP-eC9 OSCs. Furthermore, the prolonged shelf and thermal stability have been observed in OSCs with these additives. This study emphasizes the synergic effect of volatile solid additives on the performance and thermal stability of OSCs, highlighting their potential for advancing the field of photovoltaics.

Aggregation Regulation of Acceptor via Thiophene‐Substituted Alkyl Chains Enables High‐Performance Toluene‐Processed Organic Solar Cells without Additive and Post‐Treatment

AbstractDue to the mismatched aggregation behavior and limited compatibility between the donor and acceptor, it is a challenge for the active layer of organic solar cells (OSCs) to spontaneously realize well‐developed morphology in nonhalogenated solvents. In this contribution, an aggregation regulation strategy for acceptors with strong aggregation is developed via thiophene‐substituted alkyl chain engineering to fabricate high‐performance nonhalogenated solvent‐processed OSCs without an additive or post‐treatment. With the replacement of alkyl chains with steric conjugated thiophene‐substituted alkyl chains, the resulting acceptor (namely BTP‐2T, BTP‐T, and BTP‐T‐BO) shows reduced aggregation to match the polymer donor D18‐Cl using toluene as a processing solvent, enabling ordered molecular arrangement and uniform phase separation morphology. Especially, the combined modification of the asymmetric thiophene‐substituted inner chain and branched outer side chains for BTP‐T‐BO enables the formation of a superior nanoscale bi‐continuous interpenetrating network along with ordered and compact molecular packing in the D18‐Cl:BTP‐T‐BO blend. As a result, an excellent PCE of 18.05% is achieved in the D18‐Cl:BTP‐T‐BO‐based device using toluene as the processing solvent without any extra treatment, which is the highest value for nonhalogenated solvent‐processed OSCs without any extra treatment.

Hierarchical Solid-Additive Strategy for Achieving Layer-by-Layer Organic Solar Cells with Over 19 % Efficiency.

Layer-by-layer (LbL) deposition of active layers in organic solar cells (OSCs) offers immense potential for optimizing performance through precise tailoring of each layer. However, achieving high-performance LbL OSCs with distinct solid additives in each layer remains challenging. In this study, we explore a novel approach that strategically incorporates different solid additives into specific layers of LbL devices. To this end, we introduce FeCl3 into the lower donor (D18) layer as a p-type dopant to enhance hole concentration and mobility. Concurrently, we incorporate the wide-band gap conjugated polymer poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) into the upper acceptor (L8-BO) layer to improve the morphology and prolong exciton lifetime. Unlike previous studies, our approach combines these two strategies to achieve higher and more balanced electron and hole mobility without affecting device open-circuit voltage, while also suppressing charge recombination. Consequently, the power conversion efficiency (PCE) of the D18+FeCl3/L8-BO device increases to 18.12 %, while the D18/L8-BO+PFO device attains a PCE of 18.79 %. These values represent substantial improvements over the control device's PCE of 17.59 %. Notably, when both FeCl3 and PFO are incorporated, the D18+FeCl3/L8-BO+PFO device achieves a remarkable PCE of 19.17 %. In summary, our research results demonstrate the effectiveness of the layered solid additive strategy in improving OSC performance.

Hierarchical Solid‐Additive Strategy for Achieving Layer‐by‐Layer Organic Solar Cells with Over 19 % Efficiency

AbstractLayer‐by‐layer (LbL) deposition of active layers in organic solar cells (OSCs) offers immense potential for optimizing performance through precise tailoring of each layer. However, achieving high‐performance LbL OSCs with distinct solid additives in each layer remains challenging. In this study, we explore a novel approach that strategically incorporates different solid additives into specific layers of LbL devices. To this end, we introduce FeCl3 into the lower donor (D18) layer as a p‐type dopant to enhance hole concentration and mobility. Concurrently, we incorporate the wide‐band gap conjugated polymer poly(9,9‐di‐n‐octylfluorenyl‐2,7‐diyl) (PFO) into the upper acceptor (L8‐BO) layer to improve the morphology and prolong exciton lifetime. Unlike previous studies, our approach combines these two strategies to achieve higher and more balanced electron and hole mobility without affecting device open‐circuit voltage, while also suppressing charge recombination. Consequently, the power conversion efficiency (PCE) of the D18+FeCl3/L8‐BO device increases to 18.12 %, while the D18/L8‐BO+PFO device attains a PCE of 18.79 %. These values represent substantial improvements over the control device′s PCE of 17.59 %. Notably, when both FeCl3 and PFO are incorporated, the D18+FeCl3/L8‐BO+PFO device achieves a remarkable PCE of 19.17 %. In summary, our research results demonstrate the effectiveness of the layered solid additive strategy in improving OSC performance.

Small molecule perylene diimide derivatives with different bay site modifications as cathode interface layers for organic solar cells

Cathode interface layers (CILs) can effectively elevate the performance of organic solar cells (OSCs), and the development of CILs with high thickness insensitivity is the focus of commercializing OSCs. Perylene diimide (PDI) derivatives proved to be potential CILs, and bay modification could further adjust the coplanarity and optimize the film-forming properties of PDI-based CILs. Thus, two novel CILs with intermediate-sized spacer groups were synthesized (PDINN-P3P and PDINN-TPA). In contrast to PDINN-P3P with m-diphenylbenzene, PDINN-TPA with triphenylamine can form stronger self-doping between the side chain of triphenylamine and the PDI backbone, resulting in higher charge transport capacity and better interface regulation ability. PDINN-TPA-based OSCs demonstrated a higher power conversion efficiency (PCE) of 16.11 % in the PM6:Y6 system, outperforming the PCE of PDINN-P3P-based OSCs (15.00 %). Meanwhile, PDINN-TPA expressed a favorable thickness processing range, a PCE of 14.19 % can be maintained with a thickness up to 35 nm. After storing in the glove box for 114 h, PDINN-TPA-based OSCs can exhibit excellent long-term stability (over 90 % of the optimal PCE). Besides, PDINN-P3P and PDINN-TPA were further utilized CILs in the PM6: BTP-eC9 system, and the PDINN-TPA-based OSCs acquired a PCE of 16.91 % (15.54 % for PDINN-P3P-based OSCs), highlighting the broad applicability of PDINN-P3P and PDINN-TPA. This study confirms that the synergistic effect of bay site modification and n-type self-doping on PDI can simultaneously optimize the thickness insensitivity and long-term stability of PDI-based CILs.

Photovoltaic enhancement in OSCs based on PM6:Y7 when doping the active layer with Ag2S nanoparticles

Herein, silver sulfide (Ag2S) nanoparticles (NPs) with an average size of 31 nm ± 4 nm were synthesized using a simple, economic, and eco-friendly method assisted by ultrasonic bathing; the reaction was carried out in a non-polluting aqueous medium. These Ag2S NPs were suspended in ethanol and used to dope the active layer of Organic Solar Cells (OSCs) based on PM6 (donor) and Y7 (acceptor) by adding 2 v/v % of a suspension to the PM6:Y7 solution in chlorobenzene (CB). The entire fabrication process and testing was carried out under normal atmospheric conditions. Field's metal (FM) was used as the top electrode of the OSCs, which is a eutectic alloy of bismuth, indium, and tin (Bi 32.5 %, In 51 %, and Sn 16.5 %) with a melting point above 62 °C deposited by free evaporation techniques. The average Power Conversion Efficiency (PCE) for the reference and doped OSCs were 9.19 % (9.43 % the best) and 10.31 % (10.77 % the best), respectively; representing an increase of more than 14 % in the PCE value when Ag2S NPs are added to the active layer. It can be attributed to different optical phenomena, among which could be the enhance in the internal light reflection processes (scattering) and the Local Surface Plasmon Resonance (LSPR) effect.

Current Status and Advances for Polymers in the Active Layer of Organic Solar Cells

Current Status and Advances for Polymers in the Active Layer of Organic Solar Cells

Increased performance of A-DA’D-A type acceptor based organic solar cell using a thermally coevaporated cathode-modifying blend layer

The blend thin films of bathocuproine and fullerene (BCP:C60) have been thermally coevaporated to modify the active layer/cathode interfaces in organic solar cells. The BCP forms a much smaller-barrier contact with cathode than the C60. Because the surface zone of active layer is polymer donor-rich and small-molecular acceptor-deficient, C60 molecules make insufficiently large contact area with electron acceptor, leading to inefficient electron extraction. However, BCP molecules penetrate the surface of active layer, due to the smaller molecular size of BCP than that of C60, and likely form sufficiently large contact area with electron acceptor thereby to enable efficient electron extraction. Compared to conventional 10 nm BCP, 10 nm BCP:C60 (1:1 in mass ratio) enables higher efficiency based on the active layer using A-DA’D-A type acceptor, mostly because C60 constituent dissociates some excitons photogenerated in the polymer donor of surface zone and thereby increases short-circuit current density. The current research provides novel insights into the development of cathode-modifying layers for organic solar cells.

Solid additive enables efficient and stable organic solar cells by stabilizing morphology of active layer

Additive strategy is an effective method for optimizing the morphology of active layer in organic solar cells (OSCs). However, common high boiling points solvent additives may compromise device stability. In this work, 1‑bromo-8-chloronaphthalene (BCN) was used as a solid additive to improve device performance. The introduction of BCN promotes the crystallinity, H-aggregation and fibrillation of L8-BO. The active layer film with additive BCN exhibits optimized phase separation and refined fiber network, thus enhancing the exciton dissociation and charge transport in the corresponding devices. Compared with control devices (without additives), the power conversion efficiency (PCE) of optimized devices (with 20 wt % BCN) based on D18:L8-BO was increased from 17.49 % to 18.20 %. The detailed process of device fabrication is in experimental section. Furthermore, devices processed by BCN preserved 96.6 % and 96.3 % of the initial PCE after aging for 60 min with maximum power point (MPP) tracking and aging of storage for 960 h, respectively. The universality of BCN was verified in different systems, which offers promising opportunities to regulate BHJ morphology toward highly efficient OSCs.

Optimizing of Cathode Interface Layers in Organic Solar Cells Using Polyphenols: An Effective Approach

Optimizing of Cathode Interface Layers in Organic Solar Cells Using Polyphenols: An Effective Approach

A Low-Temperature Solution-Processed Nickel Oxide Nanoparticles and Phosphotungstic Acid Composite as an Anode Interface Layer for Organic Solar Cells

A Low-Temperature Solution-Processed Nickel Oxide Nanoparticles and Phosphotungstic Acid Composite as an Anode Interface Layer for Organic Solar Cells