Solid Additive Dual-Regulates Spectral Response Enabling High-Performance Semitransparent Organic Solar Cells

Semi-transparent organic solar cells (ST-OSCs) possess significant potential for applications in vehicles and buildings due to their distinctive visual transparency. Conventional device engineering strategies are typically used to optimize photon selection and utilization at the expense of power conversion efficiency (PCE); moreover, the fixed spectral utilization range always imposes an unsatisfactory upper limit to its light utilization efficiency (LUE). Herein, a novel solid additive named 1,3-diphenoxybenzene (DB) is employed to dual-regulate donor/acceptor molecular aggregation and crystallinity, which effectively broadens the spectral response of ST-OSCs in near-infrared region. Besides, more visible light is allowed to pass through the devices, which enables ST-OSCs to possess satisfactory photocurrent and high average visible transmittance (AVT) simultaneously. Consequently, the optimal ST-OSC based on PP2+DB/BTP-eC9+DB achieves a superior LUE of 4.77%, representing the highest value within AVT range of 40-50%, which also correlates with the formation of multi-scale phase-separated morphology. Such results indicate that the ST-OSCs can simultaneously meet the requirements for minimum commercial efficiency and plant photosynthesis when integrated with the roofs of agricultural greenhouses. This work emphasizes the significance of additives to tune the spectral response in ST-OSCs, and charts the way for organic photovoltaics in economically sustainable agricultural development.

Triggering the Donor-Acceptor Phase Segregation with Solid Additives Enables 16.5% Efficiency in All-Polymer Solar Cells

All-polymer solar cells have attracted considerable research interest due to their superior morphological stabilities, stretchability, and mechanical durability. However, the morphology optimization of the all-polymer bulk heterojunctions remains challenging due to the two long conjugated polymer chains, limiting its power conversion efficiency. Herein, we focus on the donor-acceptor phase segregation of an all-polymer active layer composed of PM6/PY-IT, a state-of-the-art all-polymer combination, by the introduction of volatile solid additives. Especially with 1,3-dibromo-5-chlorobenzene (DBCl) as the processing additive, we could effectively tune the miscibility between PM6 and PY-IT and thus optimize the phase segregation of the polymer donor and acceptor. Due to the synergetic effects on the favorable phase segregation and desired donor-acceptor distribution, the DBCl-treated devices feature the evident improvement of charge transport and collection, accompanied by the suppressed trap-assisted charge recombination. We consequently achieved a champion device efficiency of 16.5% (16.4% averaged), which is a 13% improvement compared with the control device without DBCl (14.6%). Our results highlight the importance of altering the miscibility of the polymer donor-acceptor pairs for practical applications of high-performance all-polymer solar cells.

Improving Cooperative Interactions Between Halogenated Aromatic Additives and Aromatic Side Chain Acceptors for Realizing 19.22% Efficiency Polymer Solar Cells

Processing additive plays an important role in the standard operation procedures for fabricating top performing polymer solar cells (PSCs) through efficient interactions with key photovoltaic materials. However, improving interaction study of acceptor materials to high performance halogenated aromatic additives such as diiodobenzene (DIB) is a widely neglected route for molecular engineering toward more efficient device performances. In this work, two novel Y-type acceptor molecules of BTP-TT and BTP-TTS with different aromatic side chains on the outer positions are designed and synthesized. The resulting aromatic side chains significantly enhanced the interactions between the acceptor molecules and DIB through an arene/halogenated arene interaction, which improved the crystallinity of the acceptor molecules and induced a polymorph with better photovoltaic performances. Thus, high power conversion efficiencies (PCEs) of 18.04% and 19.22% are achieved in binary and ternary blend devices using BTP-TTS as acceptor and DIB as additive. Aromatic side chain engineering for improving additive interactions is proved to be an effective strategy for achieving much higher performance photovoltaic materials and devices.

Solid Additive Enables Organic Solar Cells with Efficiency up to 18.6

Additive strategies play a critical role in improving the performance of organic solar cells (OSCs). There are only a few reports on the application of solid additives for OSCs, which leaves a large space for further improvement of solid additives and further study on the relationship between material structure and property. PM6:BTP-eC9-based organic solar cells (OSCs) were prepared by using a small molecule BTA3 as a solid additive, and a high energy conversion efficiency of 18.65% is achieved. BTA3 has good compatibility with the acceptor component (BTP-eC9) and optimizes the morphology of the thin films. Moreover, the introduction of a small amount of BTA3 (5 wt %) effectively promotes exciton dissociation and charge transfer and suppresses charge recombination, and the relationship between the BTA3 content and the device parameter is deeply revealed. The use of BTA3 in the active layers is an attractive and effective strategy for high-performance OSCs.

Binary Organic Solar Cells with 19.2% Efficiency Enabled by Solid Additive

Morphology optimization is critical for achieving high efficiency and stable bulk-heterojunction (BHJ) organic solar cells (OSCs). Herein, the use of 3,5-dichlorobromobenzene (DCBB) with high volatility and low cost to manipulate evolution of the BHJ morphology and improve the operability and photostability of OSCs is proposed. Systematic simulations reveal the charge distribution of DCBB and its non-covalent interaction with the active layer materials. The addition of DCBB can effectively tune the aggregation of PBQx-TF:eC9-2Cl during film formation, resulting in a favorable phase separation and a reinforced molecular packing. As a result, a power conversion efficiency of 19.2% (certified as 19.0% by the National Institute of Metrology) for DCBB-processed PBQx-TF:eC9-2Cl-based OSCs, which is the highest reported value for binary OSCs, is obtained. Importantly, the DCBB-processed devices exhibit superior photostability and have thus considerable application potential in the printing of large-area devices, demonstrating outstanding universality in various BHJ systems. The study provides a facile approach to control the BHJ morphology and enhances the photovoltaic performance of OSCs.

Formation of Efficient Quasi-All-Polymer Solar Cells by Synergistic Effect of the Ternary Strategy and Solid Additives

All-polymer solar cells (all-PSCs) have been widely studied owing to their unique mechanical flexibility and stability. However, all-PSCs have a lower efficiency than small-molecule acceptor-based PSCs. In the work, a ternary quasi-all-polymer solar cell (Q-all-PSC) using a synergy of the ternary strategy and solid additive engineering is reported. The introduction of PC₇₁BM can not only match the energy level of the photoactive materials with an improved open circuit voltage (V_OC) of the ternary devices but also enhance photon capture, which can improve short circuit current density. It is found that there is effective charge transfer between PC₇₁BM and PY-IT, which can form an electron transport channel and promote efficient charge transport. Moreover, the introduction of PC₇₁BM made the PM6/PY-IT/PC₇₁BM ternary blends more crystalline while slightly reducing phase separation, resulting in a suitable domain size. Importantly, by introducing a high dielectric-constant PFBEK solid additive as the fasten matrix, the Q-all-PSC's efficiency can reach 16.42%. This method provides a new idea for future research on all-polymer solar cells.

Enhancement of Magneto-Induced Modulus by the Combination of Filler and Plasticizer Additives-Based Magnetorheological Elastomer

Filler additive is used to provide superior bonding in rubber matrix to enhance the storage modulus of magnetorheological elastomer (MRE). However, the magneto-induced modulus is reduced as the initial storage modulus increases. Therefore, this paper aims to increase the magneto-induced modulus and maintain the initial storage modulus by combining filler and plasticizer additives. Both types of additives have different functions, where cobalt ferrite (CoFe₂O₄) is capable of enhancing the maximum storage modulus and silicone oil (SO) reduces the initial storage modulus. Thus, four MRE samples have been fabricated using (a) no additive, (b) CoFe₂O₄, (c) SO, and (d) a combination of CoFe₂O₄ and SO. The sample's hardness and magnetic properties were investigated via Durometer Shore A and Vibrating Sample Magnetometer (VSM), respectively. Furthermore, the rheological properties of MRE samples in terms of storage modulus were investigated upon the frequency and magnetic field sweep using a rheometer. The results demonstrated that the storage modulus of the MRE samples has increased with increasing the oscillation frequency from 0.1 to 50 Hz. Interestingly, the combination of additives has produced the largest value of magneto-induced modulus of 0.90 MPa as compared to other samples. Furthermore, their initial storage modulus was in between samples with SO (lowest) and without additive (highest). Therefore, fundamental knowledge in adding the combination of additives can offer solutions for a wide range of stiffness in MR device applications such as vibration and noise control devices, sensing devices, and actuators.

Pushing the Efficiency of High Open-Circuit Voltage Binary Organic Solar Cells by Vertical Morphology Tuning

The tuning of vertical morphology is critical and challenging for organic solar cells (OSCs). In this work, a high open-circuit voltage (V_OC ) binary D18-Cl/L8-BO system is attained while maintaining the high short-circuit current (J_SC ) and fill factor (FF) by employing 1,4-diiodobenzene (DIB), a volatile solid additive. It is suggested that DIB can act as a linker between donor or/and acceptor molecules, which significantly modifies the active layer morphology. The overall crystalline packing of the donor and acceptor is enhanced, and the vertical domain sizes of phase separation are significantly decreased. All these morphological changes contribute to exciton dissociation, charge transport, and collection. Therefore, the best-performing device exhibits an efficiency of 18.7% with a V_OC of 0.922 V, a J_SC of 26.6 mA cm^-2 , and an FF of 75.6%. As far as it is known, the V_OC achieved here is by far the highest among the reported OSCs with efficiencies over 17%. This work demonstrates the high competence of solid additives with two iodine atoms to tune the morphology, particularly in the vertical direction, which can become a promising direction for future optimization of OSCs.

Volatile Solid Additive-Assisted Sequential Deposition Enables 18.42% Efficiency in Organic Solar Cells

Morphology optimization of active layer plays a critical role in improving the performance of organic solar cells (OSCs). In this work, a volatile solid additive-assisted sequential deposition (SD) strategy is reported to regulate the molecular order and phase separation in solid state. The OSC adopts polymer donor D18-Cl and acceptor N3 as active layer, as well as 1,4-diiodobenzene (DIB) as volatile additive. Compared to the D18-Cl:N3 (one-time deposition of mixture) and D18-Cl/N3 (SD) platforms, the D18-Cl/N3(DIB) device based on DIB-assisted SD method exhibits a finer phase separation with greatly enhanced molecular crystallinity. The optimal morphology delivers superior charge transport and extraction, offering a champion power conversion efficiency of 18.42% with significantly enhanced short-circuit current density (J_sc ) of 27.18 mA cm^-2 and fill factor of 78.8%. This is one of the best performances in binary SD OSCs to date. Angle-dependent grazing-incidence wide-angle X-ray scattering technique effectively reveals the vertical phase separation and molecular crystallinity of the active layer. This work demonstrates the combination of volatile solid additive and sequential deposition is an effective method to develop high-performance OSCs.

Achieving over 10 % Efficiency in Poly(3-hexylthiophene)-Based Organic Solar Cells via Solid Additives

The photovoltaic performance of organic solar cells (OSCs) based on poly(3-hexylthiophene) (P3HT) has been steadily improved by developing novel non-fullerene acceptors (NFAs) in recent years. Herein, to further improve the performance of P3HT-based OSCs, a solid additive (SA4) and a typical solvent additive [1,8-diiodooctane (DIO)] were employed to process P3HT:ZY-4Cl-based OSCs, respectively. In comparison with the DIO-processed device, the SA4-processed one exhibited a more ordered molecular packing and more favorable phase separation, leading to enhanced charge transport and reduced carrier recombination. As a result, the SA4-processed device delivered a power conversion efficiency (PCE) of 10.24 %, which was much higher than that of the DIO-processed counterpart (6.26 %). This work reported a PCE over 10 % in P3HT-based OSCs for the first time, indicating the promising development of P3HT-based OSCs by morphological modulation.