Performance Of Polymer Solar Cells Research Articles

A benzobisoxazole-based polymer assisting high efficiency polymer solar cells

Ternary strategy is an effective method to optimize photovoltaic process and improve device performance. In this work, a benzobisoxazole-based conjugated polymer PBBO was designed and employed as the guest component for PM6:BTP-eC9 based devices. The polymer PBBO shows a large band gap of 2.16 eV and strong photoluminescence property, with efficient energy transfer observed between PBBO and PM6. The ternary blends not only form a cascaded energy level distribution, but also an alloy-like structure, which can effectively promote the exciton dissociation, charge transfer and efficiently suppress charge recombination. As a result, the power conversion efficiency (PCE) of the ternary device is substantially improved from 17.50% to 18.66% with the incorporation of PBBO guest component. Meanwhile, the ternary device shows good stability with retaining 86% of initial efficiency after storage for 2000 hours. This research demonstrates that the polymer PBBO would be an excellent photovoltaic material to optimize the performance of polymer solar cells.

Graphene oxide-titanium oxide-polyaniline hybrid materials for high-performance dye-sensitized solar cells

A new solar cell that comprises a graphene oxide and titanium oxide nanoparticle (NP) composite with graphitized polyaniline (PANI) has been tested in polymer solar cells (PSCs). In this study, a series of conjugated polymers were synthesized and evaluated as the absorber and hole-transport layer materials in organic solar cells, demonstrating the significant impact of the chemical structure of the polymers on solar cell performance. The incorporation of graphene oxide (GOX) and titanium oxide TiO2 NP in conjugated polymers, particularly when graphitized within the PANI layer, led to improved open-circuit voltages compared to structurally similar polymers without NP. The morphology of the composite films was analyzed and related to the photovoltaic performance of polymers synthesized with polyaniline PANI-base and PANI-salt. Optimal NP addition in PANI-salt, PANI-base, PANI-base-TiO2, and PANI-base-GOX resulted in open-circuit voltages and efficiencies of 433 mV and 3.67%, 250 mV and 0.595%, 310 mV and 1.358%, and 520 mV and 2.366%, respectively. This study underscores the importance of polymer film uniformity in the performance of PSCs, with the highest efficiency obtained using a conjugated polymer with the best PANI-salt and PANI-base-GOX films. The research sheds light on the relationship between polymer structure and device photovoltaic performance, which is crucial for the design of new polymeric materials for efficient use and stable OSCs and PSCs.

Effect of 1‐Fluoro‐2‐iodobenzene Solvent Additive on the Crystallization of Donors and Acceptors, and Ultrafast Carrier Dynamics in Polymer Solar Cells

AbstractControlled sequential crystallization of donors and acceptors is a critical factor for achieving enhanced phase separation and efficient charge transfer performance in polymer solar cells (PSCs). In this study, a comprehensive investigation of a structurally simple solvent additive, 1‐fluoro‐2‐iodobenzene (OFIB) is conducted, which efficiently controls the morphology of the active layer, resulting in fibrous assembly and significantly enhancing the power conversion efficiency from 16.34% to 18.38% based on the PM6:L8‐BO system. Density functional theory, molecular dynamics simulations, and grazing incidence small‐ and wide‐angle X‐ray scattering techniques reveal that the addition of OFIB to the processed blend aligns the orientation of the acceptor molecules, thereby enhancing the overall π–π stacking in the active layer. OFIB establishes nearly equal‐strength π–π interactions with the conjugated frameworks of both the donor and acceptor materials, benefiting from the multiple electron conjugation between its iodine atom and the conjugated framework in the active layer. Femtosecond‐timescale photophysical studies demonstrate that the OFIB‐optimized active layer shows reduced exciton losses at the donor–acceptor interface. This study offers a new perspective on the mechanism underlying the function of solvent additives and presents a comprehensive research methodology that will guide the development of next‐generation non‐fullerene acceptors for efficient PSCs.

Tethered Small-Molecule Acceptor Refines Hierarchical Morphology in Ternary Polymer Solar Cells: Enhanced Stability and 19% Efficiency.

Polymer solar cells (PSCs) are promising for efficient solar energy conversion, but achieving high efficiency and device longevity within a bulk-heterojunction (BHJ) structure remains a challenge. Traditional small-molecule acceptors (SMAs) in the BHJ blend show thermodynamic instability affecting the morphology. In contrast, tethered SMAs exhibit higher glass transition temperatures, mitigating these concerns. Yet, they might not integrate well with polymer donors, causing pronounced phase separation and overpurification of mixed domains. Herein, a novel ternary device is introduced that uses DY-P2EH, a tethered dimeric SMA with conjugated side-chains as host acceptor, and BTP-ec9, a monomeric SMA as secondary acceptor, which respectively possess hypomiscibility and hypermiscibility with the polymer donor PM6. This unique combination affords a parallel-connected ternary BHJ blend, leading to a hierarchical and stable morphology. The ternary device achieves a remarkable fill factor of 80.61% and an impressive power conversion efficiency of 19.09%. Furthermore, the ternary device exhibits exceptional stability, retaining over 85% of its initial efficiency even after enduring 1100 h of thermal stress at 85°C. These findings highlight the potential advantage of tethered SMAs in the design of ternary devices with a refined hierarchical structure for more efficient and durable solar energy conversion technologies.

Semiconductor quantum dots as a mechanism to enhance charge transfer processes in polymer solar cells

The light trapping capability of thin film polymer solar absorber, composed of poly (3-hexylthiophene) and [6,6]–phenyl C61- butyric acid methyl ester (P3HT:PC60BM) blend, is improved using ZnS semiconductor quantum dots (QD) as third donor-acceptor (D:A) component. The inherent characteristics of the microwave-assisted synthesized ZnS QD, such as quantum size effect, and multiple exciton generation were leveraged in harvesting high energy photons, which resulted in a better exciton generation, dissociation, and effective charge transport in the polymer medium. The synthesized QD exhibited good phase purity, effective kinetic enhancement, and control of the aggregation process. Hence, the impact of ZnS QD on the performance of thin film polymer solar cells (TFPSC) is evident by a remarkable improvement in the measured photovoltaic parameters. Nonetheless, it is observed that the device performances are generally dependent on the concentration of the QD in the absorber layer. Consequently, the power conversion efficiency has increased by 58% at 3% concentration of QDs by weight. This is an interesting development of TFPSC fabricated under an ambient environment.

Investigations of charge extraction and trap-assisted recombination in polymer solar cells via hole transport layer doped with NiO nanoparticles

Polymer solar cells (PSCs) are limited in their power conversion efficiency (PCE) by trap-assisted recombination caused by localized deep trap states. Therefore, developing efficient hole transport layers (HTLs) for PSCs is essential for facilitating the hole extraction stage from the photoactive layers. As part of this study, an organic/inorganic hybrid HTL was prepared by mixing synthesized nickel oxide (NiO) nanoparticles (NPs) of average size ranging from 16 to 21 nm with poly(3-hexylthiophene) (P3HT). Based on this hybrid HTL, multilayer PSCs with an ITO/ZnO/P3HT:PC61BM/P3HT:NiO NPs/MoO3/Ag structure were fabricated and characterized. As a result of the incorporation of the optimum ratio of 5 wt% NiO NPs in the P3HT layer, the PCE obtained 3.73% compared to pristine devices (2.70%) fabricated without the P3HT layer. A charge extraction by increasing voltage (CELIV) measurement confirmed enhanced hole extraction at the active layer/HTL interface. The low fluorescence emission of the P3HT/NiO NPs film enabled efficient hole extraction at the active layer/hybrid HTL interface. Adding NiO NPs beyond 5 wt% to the P3HT layer causes deep trap states to form, which facilitated trap-assisted recombination and slowed down the mobility of the holes. Consequently, we can gain insight into how to improve PSC performance with hybrid HTL.

Morphology manipulation of photoactive layer through block copolymer to improve the photovoltaic performances of polymer solar cells

Additive treatment is an effective method for manipulating the bulk heterojunction (BHJ) photoactive layer morphology of polymer solar cells (PSCs). In this work, block copolymer, polystyrene-block-poly(acrylic acid) (PS-b-PAA), was elaborately selected (according to Flory–Huggins theory) as an additive for active layer to manipulate the BHJ morphology and to enhance the photovoltaic performance of devices. As results, with a PS-b-PAA concentration of 0.4 mg/ml, the corresponding devices achieve a significant power conversion efficiency (PCE) improvement to 13.08%. By systematically analysis, the improved PCE can be ascribed to more appreciate phase separation induced by incorporation of PS-b-PAA. For the instance of the photovoltaic physical process, more suitable morphology can induce improved charge transport efficiency, suppressed bimolecular recombination and monomolecular recombination or trap-assisted recombination. In comparing, the photovoltaic performance of devices with PS-b-PAA is obviously better than that of devices with insulating polymer polystyrene (PS) and polyacrylic acid (PAA). Hence, this work checks the morphology manipulation effects of block copolymer PS-b-PAA and provides an effective and facile method to improve the morphology and photovoltaic performances of PSCs.

Suppressing charge recombination in disordered polymers blend medium

Charge recombination is one of the critical factors that influences the performance of thin film polymer solar cells (TFPSCs). In this investigation, metal, plasmonic nano-particles are employed to suppress charge recombination and energy loss in TFPSC. Trimetallic nano-composite (NC) was successfully synthesized and composed of copper, nickel, and silver (Cu/Ni/Ag) using wet chemistry. The NC was incorporated into polymer-based solar absorber layers at different concentrations. The absorber layer is a fullerene-based bulk-heterojunction design using poly-3-hexylthiophene (P3HT) donor polymer. The results show that the power conversion efficiency of the device doped with NC has improved by 85% compared to the undoped one. The incorporation of tri-metallic NC into the polymer blend solar absorber resulted in enhanced optical absorption and improved collection of photo-current as reflected by the recorded high short circuit current density (J ) and fill factor. The enhancement of the performance is due to the occurrence of local surface plasmon resonances in the polymer medium. The experiment indicated that there is some increment in an open circuit voltage, which is attributed to the low energy losses as a result of improved exciton dissociation, charge carrier transport, and collection.

Ternary solvent strategy enhancing the photovoltaic performance of ternary polymer solar cells

Ternary solvent strategy enhancing the photovoltaic performance of ternary polymer solar cells

Efficiency boost of inverted polymer solar cells using electrodeposited n-type Cu<sub>2</sub>O electrons selective transport layers (ESTLs)

Polymer solar cells (PSCs) have attracted tremendous interest as suitable candidates for harnessing solar energy in the recent years. The inherent optoelectronic properties of the inorganic transition metal oxide, negative type cuprous oxide (n-Cu2O), makes it an attractive candidate to improve the performance of PSCs when incorporated as the electron selective transport layers (ESTLs) in the device. In this study, inverted PSCs were fabricated on stainless steel (SS) substrates with n-Cu2O as the ESTL. The n-Cu2O films were prepared by electrodeposition method, followed by annealing under ambient conditions. The active layer material was prepared as bulk heterojunction blend using regioregular poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM). Poly-(4,3-ethylene dioxythiophene):poly(styrenesulphonate) (PEDOT:PSS) was used as the hole transport layer (HTL) and the final device structure was SS/n-Cu2O/P3HT:PCBM/PEDOT:PSS/Au. Annealing of the n-Cu2O ESTL in air was optimized observing the photoactive performance of the device. Optoelectronic performance of the devices was characterized using spectral response and dark and light current-voltage (I-V) measurements. n-Cu2O ESTL- incorporated devices have absorbed more photons in the short wavelength region of 450‒600 nm with the annealing of n-Cu2O ESTL due to the reduction of electron-hole recombination. The performance of the devices was significantly increased after incorporating pre-annealed n-Cu2O ESTL at 175 °C for 30 min in air. The maximum power conversion efficiency (PCE) was 0.35%.

Synergetic Effect of the Iridium Complex for Morphology Optimization in Efficient and Thermally Stable Polymer Solar Cells

Active layer morphology is one of the crucial factors for achieving excellent device performance in polymer solar cells. Recently, solid additives have drawn great attention due to their great potential in morphology control, but a detailed explanation about the working mechanism of solid additive systems is still lacking. In this work, we provided an iridium complex-based solid additive (Ir-OH) to control the morphology and crystallinity of the photoactive layer by utilizing the synergetic effect of dual additives 1-chloronaphthalene and Ir-OH. The morphology of the devices with dual additives exhibited appropriate phase separation and domain size, which provided more continuous pathways for charge transport and also exhibited condensed π–π stacking and fine molecular ordering of photoactive materials, resulting in enhanced charge collection probability. Consequently, the treatment of dual additives exhibited enhanced power conversion efficiency (PCE) with enhanced exciton dissociation, charge collection, and reduced bimolecular recombination. In addition, we found that the device with dual additives exhibited strong thermal stability under a constant heat treatment at 130 °C, and the device performance retained 65% during 24 h, showing an improved PCE of 13.89%. We expected that the favorable morphology of active materials in metal complexes can suppress thermal degradation and lead to improved device performance.

Enhanced Efficiency and Stability of Novel Pseudo-ternary Polymer Solar Cells Enabled by a Conjugated Donor Block Copolymer.

The recent breakthrough in power conversion efficiencies (PCEs) of polymer solar cells (PSCs) that contain an active layer of a ternary system has achieved values of 18-19%; this has sparked interest for further research. However, this system has difficulties in optimizing the composition and controlling the interaction between the three active materials. In this study, we investigated the use of a donor1 (D1)-donor2 (D2) conjugated block copolymer (CBP), PM6-b-TT, to replace the physical blend of two donors. PM6-b-TT, which exhibits an extended absorption range, was synthesized by covalently bonding PM6, a medium-band gap polymer, with PBDT-TT, a wide-band gap polymer. The blend films containing PM6-b-TT and Y6-BO acceptor, demonstrated excellent crystallinity and a film morphology favorable for PSCs. The corresponding pseudo-ternary PSC exhibited significantly higher PCE and thermal stability than the PM6:PBDT-TT-based ternary device. This study unambiguously demonstrates that the novel D1-D2 CBP strategy, combined with the conventional binary and ternary system advantages, is a promising material production strategy that can boost the performance of future PSCs.

Donor:Acceptor Janus Nanoparticle-Based Films as Photoactive Layers: Control of Assembly and Impact on Performance of Devices.

Water-processable organic semiconductor nanoparticles (NPs) are considered promising materials for the next-generation of optoelectronic applications due to their controlled size, internal structure, and environmentally friendly processing. Reasonably, the controllable assembly of donor:acceptor (D:A) NPs on large areas, quality, and packing density of deposited films, as well as layer morphology, will influence the effectiveness of charge transfer at an interface and the final performance of designed optoelectronic devices.This work represents an easy and effective approach for designing self-assembled monolayers of D:A NPs. In this self-assembly procedure, the NP arrays are prepared on a large scale (2 × 2 cm2 ) at the air/water interface with controlled packing density and morphology. Due to the unique structure of individual D:A Janus particles and their assembled arrays, the Janus nanoparticle (JNP)-based device exhibits an 80% improvement of electron mobility and more balanced charge extraction compared to the conventional core-shell NP-based device. An outstanding performance of polymer solar cells with over 5% efficiency is achieved after post-annealing treatment of assembled arrays, representing one of the best results for NP-based organic photovoltaics. Ultimately, this work provides a new protocol for processing water-processable organic semiconductor colloids and future optoelectronic fabrication.

Revealing the spacing effect of neighboring side‐chains in modulating molecular aggregation and orientation of M‐series acceptors

AbstractControlling the aggregation of small‐molecule acceptors (SMAs) is essential to obtain an optimal morphology and to improve the photovoltaic performance of polymer solar cells (PSCs). However, reducing intermolecular aggregation of SMAs is usually accompanied by the disruption of compact molecular packing thereby leading to their decreased electron mobilities. Here, two novel M‐series SMAs (MD1T and MD2T) based on ladder‐type heterononacenes with neighboring side‐chains separated by one or two thiophene rings are designed and synthesized. It is found that shortening the spacing of the neighboring side‐chains of the SMAs can greatly alleviate the intermolecular aggregation and alter the molecular orientation from bimodal edge‐on/face‐on to predominant face‐on while maintaining the compact molecular packing. As a result, a more favorable morphology with smaller domain sizes is formed for the MD1T‐based blend films, which greatly improves the charge generation and charge transport for the corresponding PSCs. The best‐performing MD1T‐based device affords an efficiency of 12.43%, over seven times higher than that of the MD2T‐based device. This work reveals the importance of the spacing between the neighboring side‐chains in modulating the molecular aggregation and active layer morphology, and the obtained structure‐performance relationships shall provide important guidance for designing highly efficient SMAs.

Improved performance for polymer solar cells though photon energy harvesting and down-conversion of Eu3+-induced diblock polymer aggregates (EIPAs)

Eu3+-induced diblock polymer aggregates (EIPAs) were synthesized by self-assembly method and doped into the active layer of various non-fullerene systems to improve the power conversion efficiency (PCE) and stability of the devices.

In situ performance and stability tests of large-area flexible polymer solar cells in the 35-km stratospheric environment.

Flexible organic solar cells (FOSCs) are one of the most promising power sources for aerospace aircraft due to their attractive advantages with high power-per-weight ratio and excellent mechanical flexibility. Understanding the performance and stability of high-performance FOSCs is essential for the further development of FOSCs for aerospace applications. In this paper, after systematic investigations on the performance of the state-of-the-art high-performance solar cells under thermal cycle and intensive UV irradiation conditions, in situ performance and stability tests of the solar cells in the 35km stratospheric environment were carried out through a high-altitude balloon uploading. The encapsulated FOSCs with an area of 0.64cm2 gave the highest power density of 15.26mW/cm2 and an efficiency over 11%, corresponding to a power-per-weight ratio of over 3.32kW/kg. More importantly, the cells showed stable power output during the 3-h continuous flight at 35km and only 10% performance decay after return to the lab, suggesting promising stability of the FOSCs in the stratospheric environment.

High-level periodic conjugated terpolymers through AA/BB monomer pair-type terpolymerization improve performance of polymer solar cells

With a growing interest in developing high-performance π-conjugated terpolymers via random terpolymerization, new synthetic approaches resulting in higher-quality terpolymers with improved backbone regularity are needed to help make organic optoelectronic and photovoltaic applications more prosperous. Herein, we report an AA/BB monomer pair-type terpolymerization protocol that renders semi-sequence-controlled (SSC) terpolymers by polymerizing the aperiodically repeating units into the preferentially formed periodic, alternating polymeric block sequences, unlike the conventional random terpolymerization for producing terpolymers with irregular repeating sequences. A close comparison of SSC- and conventional terpolymerization-derived terpolymers indicate detectable differences in the absorption, energetic properties, carrier transport, energy loss, and morphological characteristics. The optimal SSC terpolymer-based polymer solar cells (PSCs) outperform the conventional terpolymerization-derived counterparts in power conversion efficiency (PCE). Moreover, the optimal SSC terpolymer-based PSCs processed by an eco-friendly solvent/additive system also exhibit outstanding PCEs of 16.52 % (small area of 0.041 cm2) and 15.50 % (large area of 1 cm2). To the best our knowledge, it is the highest value among tetrahydrofuran-processed PSCs. This SSC terpolymerization shows considerable promise in synthesizing high-quality in-chain terpolymers with high backbone sequence control without sacrificing their inherent beneficial features, providing high potential for further improving their PSC performances.

Composition-Tolerant Terpolymers for Efficient, Nonhalogenated Solvent-Processed Polymer Solar Cells

The design of terpolymers is a compelling strategy to improve the polymer solar cell (PSC) performance. However, the terpolymer composition at which the power conversion efficiency (PCE) of associated PSCs is typically optimized generally falls within a very narrow range, complicating the reproducible fabrication of optimal PSCs. In this study, a series of D–A1–D–A2 type random terpolymers (DTTz-X, where X = 10–60) is designed with structurally similar A1 and A2 accepting units. The sulfur atom of the benzothiadiazole subunit in the A1 (DTBT) unit is replaced by a nitrogen atom in the A2 (DTTz) unit, enabling the introduction of an alkyl solubilizing group while maintaining the overall structural properties of the terpolymer system. Consequently, the DTTz-X PDs maintain good optoelectronic properties at various A1/A2 ratios, while their processability in nonhalogenated solvents is significantly enhanced. Accordingly, the PSC performance of the terpolymer system shows good composition tolerance; i.e., the terpolymer system affords PSCs with PCEs exceeding 15% (up to 16.4%) over a broad range of DTTz compositions (10–40 mol %). This study establishes a useful design strategy for the development of efficient terpolymer donors for reproducible and eco-friendly fabrication of high-performance PSCs.

Tri‐metallic quantum dot under the influence of solvent additive for improved performance of polymer solar cells

AbstractCdTeSe colloidal quantum dot (QD) was used to enhance photon capture in thin film polymer solar cells (TFPSC). The QDs were synthesized in aqueous media from two different precursors. Bulk heterojunction (BHJ) polymer blends composed of P3HT and PCBM were used as an absorber layer of the solar cell to investigate the effect of QDs. Different concentrations of QDs were used in the polymer matrix, which significantly impacted the power conversion efficiency (PCE) of the doped devices. More device performance growth was recorded by employing a small amount of solvent additives to disperse the QDs and increase the polymer's crystallinity in the medium. Hence, the addition of 1, Chloronaphthalene (CN) solvent additive in the QD‐doped bulk heterojunction film further enhanced the overall performance of the TFPSC due to improved film morphology that has significantly influenced the charge transport processes. Consequently, the PCE of the solar cell increased by nearly 50% compared to the pristine TFPSC due to the effect of solvent additives.

Improving the Performance of Polymer Solar Cells with Benzo[ghi]perylenetriimide-Based Small-Molecules as Interfacial Layers.

In this study, we prepared three benzo[ghi]perylenetriimide (BPTI) conjugated molecules as electron-transporting surface-modifying layers for polymer solar cells (PSCs). These three BPTI derivatives differed in the nature of their terminal functionalities, featuring butylamine (C3NH2), propylammonium iodide (C3NH3I), and butyldimethylamine (C3DMA) units, respectively. We evaluated the optoelectronic properties of PTB7-Th: PC71BM blends modified with these interfacial layers, as well as the performance of resulting PSCs. We used UV–Vis spectroscopy, atomic force microscopy, surface energy analysis, ultraviolet photoelectron spectroscopy, and photoelectric flow measurements to examine the phenomena behind the changes in the optoelectronic behavior of these blend films. The presence of a BPTI derivative changed the energy band alignment at the ZnO–active layer interface, leading to the ZnO film behaving more efficiently as an electron-extraction electrode. Modifying the ZnO surface with the BPTI-C3NH3I derivative resulted in a best power conversion efficiency (PCE) of 10.2 ± 0.53% for the PTB7-Th:PC71BM PSC (cf. PCE of the control device of 9.1 ± 0.13%). In addition, modification of a PM6:Y6:PCBM PSC with the BPTI-C3NH3I derivative increased its PCE from 15.6 ± 0.25% to 16.5 ± 0.18%. Thus, BPTI derivatives appear to have potential as IFLs when developing high-performance PSCs, and might also be applicable in other optoelectronic devices.