Small Molecule Electrolytes Research Articles

N-type small molecule electrolyte cathode interface layer with thickness insensitivity for organic solar cells

Interface engineering has a critical impact on the performances of organic solar cells (OSCs). And cathode interface layer (CIL) with thickness insensitivity is urgently pursued to improve the possibility of industrialization of OSCs. N-type self-doping has been proven effective in increasing electron mobility. Here, four novel n-type small molecule electrolytes (SMEs) with diverse counter anions (CAs), PDIN-BF4, PDIN-BPh4, PDIN-BPhF4, and PDIN-BIm4 were synthesized and employed as cathode interface layers (CILs). Among them, PDIN-BIm4-based OSCs with PM6:Y6 active layer achieved the most glorious electron mobility and thickness insensitivity with a power conversion efficiency (PCE) of 16.98 % due to outstanding self-doping effect and interfacial regulation ability. However, the multi-F atoms on PDIN-BPhF4 may prevent self-doping progress and impede electron transport, thus leading to a low PCE of 11.53 %. Meanwhile, the PDIN-BIm4-based device can maintain over 80 % of the optimal PCE with a thickness of 43 nm or storing in a glove box for 600 h. In addition, PM6: BTP-eC9-based device with PDIN-BIm4 CIL acquired a PCE of 17.82 %, highlighting the broad applicability of PDIN-BIm4. Our work demonstrates that the introduction of CAs into n-type organic materials helps promote the progress of efficient and stable OSCs.

Synthesis and characterization of small molecular electrolyte as an interlayer and its application in organic solar cells

A small molecule electrolyte (SME) based on the iodide ion (FN-NDI-I) was synthesized for organic solar cells as interlayers based on fullerene and non-fullerene systems. The utilization of ITO/ZnO/SME enhances the PCE of the fullerene-based device, with an increase observed from 8.63% (pristine ZnO) to 9.06%. In the non-fullerene case, the PCE of the device based on pristine ITO/ZnO reaches 14.9%. However, due to leakage current, the performance of the device using the ITO/ZnO/SME interlayer decreases to 11.5%. When ITO/SME is employed, the device attains a PCE of 14.5%, which closely approximates the performance of the non-fullerene device based on ITO/ZnO.

A simple approach for fabrication of low-temperature processible inverted organic solar cells

Small molecule electrolytes (SMEs) based on naphthalene diimide with various types of side chains, such as tosylate anion and zwitterion were synthesized for photovoltaic application as the cathode interlayer. These materials utilizedthe side chains to produce a beneficial interface dipole. With PM6:Y6BO as the active layer, the device based on NDIN-BS exhibited a PCE of 14.5%, which is almost the same as the PCE of the ZnO-based device (15.0%). The device based on NDIN-OTs exhibited a lower PCE of 14.2%, which mainly resulted from the significant decrease of the Jsc, but exhibit a higher FF due to the better contact with the active layer. This outcome showed that SMEs are suitable candidates to adjust the work function of ITO and provide an alternative to the ZnO interlayer, which relies on proper monitoring of the sol–gel transition by high annealing temperatures as high as 200 °C, leading to simplifying the manufacture of cost-effective OSCs.

Enhanced efficiency in organic solar cells by incorporation of small molecule based on tosylate anion

A small molecule electrolyte (SME) based on tosylate anion (FN-NDI-OTs) was synthesized and applied as the cathode interlayer in organic solar cells (OSCs). This material generates a beneficial interface dipole at the cathode interface by the tosylate anion functionality, leading to the improvement of power conversion efficiency (PCE). The device based on the blend of PTB7-Th:PC71BM as the active layer exhibits improved PCE, increasing from 8.79% based on pristine ZnO to 9.53% using the ZnO/SME as the interlayer, which mainly resulted from the enhancement. These results indicate the potential of SME with tosylate anion as an interlayer in OSCs.

Effect of environmental factors on the aggregation behavior of astaxanthin in water

Molecular aggregation is a common phenomenon widely found in natural organisms, which is crucial for some specific functions of biological systems. To study the aggregating behavior of hydrophobic carotenoids in water, astaxanthin was employed and dispersed under different surroundings to induce aggregation. The results showed that astaxanthin tended to form J- or H-type aggregates when the water content was higher than 60%. Both hydrochloric acid (HCl) and sodium hydroxide (NaOH) were beneficial for the formation of astaxanthin J-aggregates, but they were not good for inducing H-aggregates. Small-molecule electrolytes, like sodium salts, mostly played an enormous hindrance role to the formation of astaxanthin H- and J-aggregates, except for sodium chloride (NaCl) which helped astaxanthin to form J-aggregates. Both sodium periodate (NaIO4) and sodium acetate (CH3COONa) could prevent the formation of astaxanthin H- and J-aggregates, but sodium chloride (NaCl) could only hinder the formation of H-aggregates. As for polyelectrolytes chitosan and DNA, the difference of chain structure led to different aggregation effects. The soft single chain of chitosan tended to induce J-aggregates formation, while double-stranded DNA preferred to guide the formation of H-aggregates. By choosing and integrating the advantageous environmental factors that facilitate each type of astaxanthin aggregates, J- and H-type astaxanthin aggregates were stably loaded in DNA/CS nanoparticles with distinct particle sizes. Controlled preparation of either H- or J-type aggregates is of great significance for further studies concerning the structure–activity relationship of carotenoid aggregates.

Efficiency enhancement of organic solar cell by small molecule electrolyte based on naphthalene diimide as an electron transport layer

As an electron transport layer (ETL) for organic solar cells (OSCs), a naphthalene diimide (NDI)-based alcohol-soluble small molecule electrolyte (FN-NDI-Br) was designed and synthesized. The small molecule electrolyte was synthesized from the quaternization of the amino-terminal group in the alkyl chain. A bulk heterojunction (BHJ)-based inverted OSCs with the ITO/ZnO/ETL/PTB7-Th:PC71BM/MoO3/Ag structure were fabricated. The power conversion efficiency (PCE) enhancement was achieved by inserting a small molecule electrolyte as the interlayer. The device performance of the device with the PTB7-Th and PC71BM blend as the photoactive layer and FN-NDI with acetic acid additive as ETL was enhanced over the device with pristine ZnO from 8.53% to 8.78%. The performance of the device was enhanced up to 9.16% by modifying the side chain functionality compared with the device with a FN-NDI interlayer.

Electrolytic conductivity of ionic polymers in a nonpolar solvent.

The electrolytic conductivity of two electrolytes as solutions in the nonpolar solvent, n -dodecane, as a function of concentration has been studied. One was a small molecule electrolyte (tetraalkyl cation and a highly fluorinated tetraphenylborate anion), and the other was a macromolecular electrolyte (cation-containing poly(alkyl methacrylate) chain with the same anion). Two series of the macromolecular cation were prepared: one with entirely cation-containing molecules and the other with a small proportion (10%) cation-containing and the rest nonionic. The conductivity data were qualitatively similar for all systems, which formed both single ions and triple ions. The data from the two series of macromolecular electrolytes were particularly informative to understand some recent and counterintuitive electrokinetic data for particles that were stabilized by these polymers. Reducing the proportion of cationic chains in the stabilizer of the particles was found to increase their electrophoretic mobility. In the conductivity data in this study, reducing the proportion of cationic chains in solution was found to increase the magnitude of the single-ion equilibrium constant and suppress the formation of triple ions. These data should support the development of models to understand these electrokinetic results.

Enhanced efficiency of organic solar cells via Si-based non-conjugated small-molecule electrolyte as cathode interlayer

Abstract As an important approach to commercialize organic solar cells (OSC), research on solution-processable and low-cost interfacial materials with universal applicability has attracted much attention. In this work, three new non-conjugated small-molecules electrolytes (NCSMEs) with silicon as the core atom and sulfonate ion as the terminal group were synthesized, which were further applied as cathode interlayers (CILs) in non-fullerene and fullerene based OSCs. As the result, the power conversion efficiency (PCE) of 15.57% for non-fullerene PM6:Y6-based and 8.96% for fullerene PTB7:PC71BM-based device was obtained, respectively. The improved performance was mostly attributed to the NCSMEs CILs which could mediate the energy barrier to form a better ohmic contact, enhance the charge transmission and collection efficiency, and decrease the charge recombination. It is noteworthy that the synthesized CILs could provide a new strategy for the potential applications of low-cost and highly efficient OSCs.

Dipolar hole-blocking layers for inverted perovskite solar cells: effects of aggregation and electron transport levels

Herein, we report on the synthesis and investigation of two triazino-isoquinoline tetrafluoroborate electrolytes as hole-blocking layers in methylammonium triiodide perovskite photovoltaic devices with fullerene electron extraction layer. We find that increasing the thickness of the dipolar hole-blocking layer results in a gradual increase in the open-circuit voltage suggesting that aggregation of the molecules can enhance the dipole induced by the layer. This finding is confirmed by theoretical calculations demonstrating that while both molecules exhibit a similar dipole moment in their isolated state, this dipole is significantly enhanced when they aggregate. Ultra-violet photoemission spectroscopy measurements show that both derivatives exhibit a high ionization potential of 7 eV, in agreement with their effective hole-blocking nature demonstrated by the devices. However, each of the molecules shows a different electron affinity due to the increased conjugation of one of the derivatives. While the change in electron transport level between the two derivatives is as high as 0.3 eV, the difference in the open-circuit voltage of both types of devices is negligible, suggesting that the electron transport level plays only a minor role in determining the open-circuit voltage of the device. Numerical device simulations confirm that the increase in built-in potential, arising from the high dipole of the electrolyte layer, compensates for the non-ideal energetic alignment of the charge transport levels, resulting in high open-circuit voltages for a range of electron transport levels. Our study demonstrates that the application of small molecule electrolytes as hole-blocking layer in inverted architecture perovskite solar cells is a powerful tool to enhance the open-circuit voltage and provides useful guidelines for designing future generations of such compounds.

Small-molecule electrolytes with different ionic functionalities as a cathode buffer layer for polymer solar cells

Small-molecule electrolytes were designed and synthesized as the cathode interlayer in inverted polymer solar cells.

Enhanced p-Type Work Function Tunability Induced by Electrostatic Molecular Alignment and Surface Coverage in Conjugated Small-Molecule Electrolyte

We report that a chemically p-doped conjugated small-molecule electrolyte (CSE) can be used as a strong and uniform dipole array for highly efficient optoelectronic devices via electrostatically in...

Simultaneous Bottom-Up Interfacial and Bulk Defect Passivation in Highly Efficient Planar Perovskite Solar Cells using Nonconjugated Small-Molecule Electrolytes.

Recent perovskite solar cell (PSC) advances have pursued strategies for reducing interfacial energetic mismatches to mitigate energy losses, as well as to minimize interfacial and bulk defects and ion vacancies to maximize charge transfer. Here nonconjugated multi-zwitterionic small-molecule electrolytes (NSEs) are introduced, which act not only as charge-extracting layers for barrier-free charge collection at planar triple cation PSC cathodes but also passivate charged defects at the perovskite bulk/interface via a spontaneous bottom-up passivation effect. Implementing these synergistic properties affords NSE-based planar PSCs that deliver a remarkable power conversion efficiency of 21.18% with a maximum VOC = 1.19 V, in combination with suppressed hysteresis and enhanced environmental, thermal, and light-soaking stability. Thus, this work demonstrates that the bottom-up, simultaneous interfacial and bulk trap passivation using NSE modifiers is a promising strategy to overcome outstanding issues impeding further PSC advances.

New small molecule electrolytes based on tosylate anion for organic solar cells

Reduction of a Schottky barrier between the active layer and electrodes can play an important role enhancing the power conversion efficiency (PCE) of organic solar cells (OSCs), which originated from a favorable interface dipole at the cathode interface. Herein, two new small molecules (SM) electrolytes based on tosylate anions, named 2,2’-(ethane-1,2-diylbis(oxy))bis(N,N,N-trimethylethananminium) benzenesulfonate (TEG-M-OTs) and 1,1'-bis(1-dodecyl)-4,4′-bipyridine-1,1′-diium benzenesulfonate (V-C12-OTs), were synthesized to induce the reduction of a Schottky barrier in OSCs. The PCE of devices based on ZnO with TEG-M-OTs or V-C12-OTs as the cathode buffer layer (CBL) was enhanced from 7.48% to 7.74% and 7.88%. In case of ZnO-free devices, the PCE of TEG-M-OTs or V-C12-OTs was achieved up to 4.22% and 6.95%, respectively. The Kelvin probe microscopy was performed by measuring the work function (WF) of SM electrolytes with or without ZnO on the ITO surface. It showed that the WFs of SM electrolytes coated ITO are closer to - 4.02 eV, the lowest unoccupied molecular orbitals (LUMO) of the acceptor, than the WF of MeOH treated ITO with ZnO (- 4.37 eV).

Enhancing the Open‐Circuit Voltage of Perovskite Solar Cells by up to 120 mV Using π‐Extended Phosphoniumfluorene Electrolytes as Hole Blocking Layers

AbstractFour π‐extended phosphoniumfluorene electrolytes (π‐PFEs) are introduced as hole‐blocking layers (HBL) in inverted architecture planar perovskite solar cells with the structure of ITO/PEDOT:PSS/MAPbI3/PCBM/HBL/Ag. The deep‐lying highest occupied molecular orbital energy level of the π‐PFEs effectively blocks holes, decreasing contact recombination. It is demonstrated that the incorporation of π‐PFEs introduces a dipole moment at the PCBM/Ag interface, resulting in significant enhancement of the built‐in potential of the device. This enhancement results in an increase in the open‐circuit voltage of the device by up to 120 mV, when compared to the commonly used bathocuproine HBL. The results are confirmed both experimentally and by numerical simulation. This work demonstrates that interfacial engineering of the transport layer/contact interface by small molecule electrolytes is a promising route to suppress nonradiative recombination in perovskite devices and compensates for a nonideal energetic alignment at the hole‐transport layer/perovskite interface.

Hyperbranched small-molecule electrolyte as cathode interfacial layers for improving the efficiency of organic photovoltaics

Small-molecule electrolytes (SMEs) have attracted increasing interests owing to their intrinsic advantages, such as high repeatability, easy purification and well-defined structures. Interfacial engineering plays crucial roles in enhancing the power conversion efficiency (PCE) of polymer solar cells (PSCs). Through a green route one-step reaction with nonhalogen solvent, we reported the design and synthesis of one novel hyperbranched SME PNSO 3 Na as cathode interfacial layer (CIL). Owing to containing seven moles butyl sulfonate sodium, hyperbranched SMEs PNSO 3 Na CIL can form interfacial dipoles, tune the interfacial energy alignment, realize environment-friendly water/alcohol processing, induce the upper active layer to form order morphology and enhance the PCE of PSCs. Based on P3HT–PC61BM active layer, the PCE of the device based on PNSO 3 Na CIL was dramatically enhanced from 0.8 to 3.7% compared to the bare ITO device.

Application of automated peritoneal dialysis in urgent-start peritoneal dialysis patients during the break-in period

ObjectiveWhether automated peritoneal dialysis (APD) is a feasible strategy for urgent-start peritoneal dialysis (PD) therapy during the break-in period remains unclear. This study was conducted to compare the efficacy as well as complications among three PD modes during the break-in period.MethodsNinety-six patients treated with urgent-start PD after catheterization were retrospectively analyzed. Patients were divided into three groups, incremental continuous ambulatory PD (CAPD) group (n = 26); APD group (n = 42); and APD–CAPD group (n = 28). Clinical parameters at the end of the break-in period and 1 month after the initiation of PD treatment were collected and analyzed.ResultsCompared with the traditional incremental CAPD, APD and APD–CAPD were superior as they could effectively remove small-molecule uremic toxins and correct electrolyte imbalance (P < 0.05), while did not increase the incidence of early complications during the break-in period (P > 0.05). However, APD led to a significant decline in albumin and pre-albumin, as compared with APD–CAPD and CAPD (P < 0.05). A PD strategy consisting 6 days of APD and 3 days of CAPD showed a great advantage in preventing excessive protein loss. There were no significant differences in all tested biochemical parameters among the three groups at 1 month after treatment (all P > 0.05).ConclusionApplication of APD for urgent-start PD during the break-in period is feasible. A combination of APD and CAPD regimens seems to be a more reasonable mode.

Highly efficient non-fullerene polymer solar cells enabled by novel non-conjugated small-molecule cathode interlayers

Water/alcohol soluble small molecule electrolytes were successfully employed as cathode interlayers to improve the performance of non-fullerene polymer solar cells.

A Simple Approach to Fabricate an Efficient Inverted Polymer Solar Cell with a Novel Small Molecular Electrolyte as the Cathode Buffer Layer.

A novel small-molecule electrolyte, 1,1'-bis(4-hydroxypropyl)-[4,4'-bipyridine]-1,1'-diium bromide (V-OH), containing a mixture of PTB7:PC71BM has been designed and synthesized as a cathode buffer layer for inverted polymer solar cells (iPSCs). The molecular structure of this new compound comprises a viologen skeleton with hydroxyl group terminals. While the viologen unit is responsible for generating a favorable interface dipole, the two terminal hydroxyl groups of V-OH may generate a synergy effect in the magnitude of the interface dipole. Consequently, the devices containing the V-OH interlayer exhibited a power conversion efficiency (PCE) of 9.13% (short circuit current = 17.13 mA/cm2, open circuit voltage = 0.75 V, fill factor = 71.1%). The PCE of the devices with V-OH exhibited better long-term stability compared to that of the devices without V-OH. Thus, we found that it is possible to enhance the efficiency of PSCs by a simple approach without the need for complicated methods of device fabrication.

Realizing High Performance Inverted Organic Solar Cells via a Nonconjugated Electrolyte Cathode Interlayer

Organic electrolyte interlayer has been widely used in organic solar cells (OSCs). However, previous reports mainly focused on conventional OSCs despite with poor stability. In more stable inverted OSCs, the application of organic electrolyte interlayer is rarely reported and the device efficiency is low. Here, a simple nonconjugated small molecule electrolyte (SME), ethylene diamine tetraacetic acid tetrasodium (EDTA-4Na), is successfully introduced into inverted OSCs as a cathode interlayer, leading to a high efficiency of 9.69%. Besides efficiency, the device stability is also improved and almost 85% of the efficiency can be maintained even after storage of 46 days. More importantly, EDTA-4Na tremendously alleviates the hysteresis phenomenon happening in organic optoelectronic devices based on ionized interlayer. As a result, stabilized power output of ∼9.5% is obtained in OSCs with EDTA-4Na. These inspiring results prove that electrolytes with simple structure can also achieve excellent performance an...

Properties of inverted polymer solar cells based on novel small molecular electrolytes as the cathode buffer layer

Novel small-molecule electrolytes were designed and synthesized for use in the cathode interlayer in bulk-heterojunction polymer solar cells (PSCs). The synthesized materials consist of polar quaternary ammonium bromide with the addition of multiple hydroxyl groups, which are N,N,N,N,N,N-hexakis(2-hydroxyethyl)butane-1,4-diaminium bromide (C4) and N,N,N,N,N,N-hexakis(2-hydroxyethyl)hexane-1,6-diaminium bromide (C6). The materials generate a favorable interface dipole through the quaternary ammonium bromide. In addition, the multiple polar hydroxyl groups increased the interface dipole magnitude. The power conversion efficiency of the devices with the interlayer was up to 9.20% with a Jsc of 17.22 mA/cm2, a Voc of 0.75 V, and an FF of 71.3%. The PCE of devices with an interlayer show better long-term stability than a device without an interlayer. Our strategy shows that it is possible to enhance the efficiency of PSCs by simple approaches without complicated syntheses.