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Using solvent additives to optimize the morphology of the blend films in organic solar cells (OSCs) is a simple and effective method. Here, methyl salicylate (MeSA) is used as a non‐halogen additive for inverted OSCs, and the impact of this additive on the blend film and photovoltaic performance is carefully investigated. The significant increase in short‐circuit current density (JSC) and fill factor (FF) leads to a significant improvement in device performance, which is caused by bicontinuous interpenetrating phase separation and balanced charge transport. The results indicate that MeSA modulates the phase distribution and promotes the accumulation of ordered molecules in the blend film, thus exhibiting an efficiency of 9.45% and improved FF (>70%) with a 7% MeSA additive. Most importantly, MeSA can be added in large doses (7%) compared to other traditional solvent additives (e.g., 1,8‐diiodooctane, 1‐chloronaphthalene, etc.), indicating that its concentration variation has little effect on performance and is conducive to repeatable, large‐scale production, which is of great importance for industrialization. [ABSTRACT FROM AUTHOR]

In this article, we discuss a straightforward method of parameter extraction, which was used in two back-to-back connected Schottky diodes previously. We verified the universality and feasibility of this method by extracting the solar cell parameters from J to V curves. This method provides a flexible approach to extract parameters of some complex models that are impracticable using other methods. In addition, we discussed the authenticity problem for parameter extraction and its widely used solution, deforming the formula by using some approximation to make the object parameter the slope or intercept. We argued that it is necessary to analyze how the error transformed into the deductive curve, which is generally overlooked. Moreover, we illustrated the defect of the ordinary least squares method under the absolute least squares criterion. Under some conditions, such as when the point under larger coordinates has a larger error, it is more accurate to use the least squares method under the relative least-squares criterion. [ABSTRACT FROM AUTHOR]

For organic photovoltaic cells, the development of new green solvents and nontoxic and halogen‐free additives is an urgent issue. Here, a simple combination of o‐xylene (O‐XY) and ethyl 2‐hydroxybenzoate (EHB) is introduced in inverted devices based on poly[4,8‐bis(5‐(2‐ethylhexyl)‐thiophene‐2‐yl) benzo[1,2‐b;4,5‐b′] dithiophene‐2,6‐diyl‐alt‐(4‐(2‐ethylhexyl)‐3‐fluorothieno[3,4‐b] thiophene)‐2‐carboxylate‐2‐6‐diyl]:[6,6]‐phenyl‐C71‐butyric acid methyl ester (PTB7‐Th:PC71BM) as blend layers, the device performance reaches optimal values (9.29%) when O‐XY and 3% EHB are introduced as additives, accompanied by the maximum fill factor (67.5%) and JSC (17.20 mA cm−2). From the results of characterization analysis, it is clear that EHB additive improves the crystallinity of the donor by regulating the kinetic process of active layer formation, selectively solubilizes the more aggregated fullerene acceptors, which allows PTB7‐Th to enter the conformational domain of PC71BM, and accelerates the molecular rearrangement. Besides, the EHB additive not only reduces the recombination, increases the carrier migration rate but also promotes the crystallinity of the donor, resulting in a tighter stacking. This work provides a green combination of solvents and additives that is important for the mass production of solar cells. [ABSTRACT FROM AUTHOR]

• A PCE over the 13% for ternary PSCs based on ternary polymer donor was achieved. • Morphology studies confirmed that ternaty PSC brought most appropriate phase separation. • A classical ternary strategy could significantly improve charge extraction. The third component played an increasingly significant role in polymer solar cells (PSCs), especially for the morphological impact. Here, we use a ternary polymer donor (TBFCl50-BDD) and organic small molecule acceptor (BTP-4F) as the main material and introduce a third component (PC 71 BM) to enhance the morphology of the photoactive layer and result in improved device performance. The TBFCl50-BDD:BTP-4F based PSCs only exhibited an efficiency of 10.58%, while The power conversion efficiency of ternary device (TBFCl50-BDD:BTP-4F:PC 71 BM) reached 13.15%. Importantly, the introduction of PC 71 BM can not only improve the morphology of the active layer and promote more efficient exciton transport, but also influence the molecular arrangement for better crystallization performance. This work offers an effective method for optimization of the morphology to enhance the properties of PSCs. [ABSTRACT FROM AUTHOR]

• A halogen-free additive, dibenzyl ether, was successfully introduced into PSCs. • The dibenzyl ether additive could boost the phase composition distribution. • The morphology, exciton dissociation, charge transport ability can be improved. Conventional additives like 1,8-diiodooctane (DIO) and 1-chloronaphthalene (CN) play an essential role in optimization of blend film morphology of polymer solar cells (PSCs). However, they have halogenated elements in their end groups, which are harmful to the environment and humans, limiting large-scale applications. In this work, a novel non-toxic and non-halogen additive, dibenzyl ether (DE), was introduced into PTB7-Th:PC 71 BM based PSCs, and the role of the DE additive was systemically investigated. The results showed that DE additive can not only adjust phase separation and optimize the morphology of blend film, but also promote the mobility of hole and electron. The grazing-incidence small-angle X-ray scattering (GISAXS) showed that the introduction of DE increased the interface area between PTB7-Th and PC 71 BM, which can promote exciton dissociation, and achieve better charge transport. Transient photovoltage (TPV) and transient photocurrent (TPC) measurements show that carrier recombination of the additive-containing devices can be effectively inhibited with improved charge transport efficiency of the active layer. Consequently, the devices with DE additive achieve power conversion efficiency (PCE) of 9.53% and a fill factor (FF) of 70.41%. Our non-toxic and non-halogen additive provides a potential solution for the preparation of environmental-friendly PSCs in the future. [ABSTRACT FROM AUTHOR]

Polymer cathode interface materials with self-doped properties have been extensively researched for application in organic solar cells (OSCs) to strengthen the ohmic contact between the photoactive layer and the electrode. Here, three new n-type polymeric interfacial materials were designed and synthesized with self-doping effects. The self-doping behavior, water contact angle, conductivity, work function of three materials were systematically investigated. Subsequently, these three novel n-type materials were successfully applied as cathode interface layers (CILs) in PTB7-Th:PC 71 BM-based OSCs and could achieve a remarkable power conversion efficiency of 9.01%. It was found that the number and position of polar groups have a strong influence on the electrical conductivity, tunable work function and interfacial interactions of these polymers. These results suggest that simple adjustment of the position and number of polar groups can provide an effective method for developing efficient CILs for high-performance OSCs. [Display omitted] • Three new naphthalenediimines based cathode interfacial materials were synthesized. • PNDI-FN, PNDI-N-F and PNDI-N-FN have different numbers and positions of polar groups. • Modulating the position and number of polar groups enhanced the device performance. • Achieved high PCE of 8.27%, 8.48% and 9.01% for PNDI-FN, PNDI-N-F and PNDI-N-FN, respectively. [ABSTRACT FROM AUTHOR]

Interfacial engineering plays a key role in the performance enhancement of organic solar cells (OSCs), which has a significant impact on the charge collection and transport in the devices. Herein, the conventional devices based on PTB7-Th:PC 71 BM were prepared by introducing a non-conjugated small molecule tetrasodium iminodisuccinate (IDS) as an electron transport layer (ETL). It is shown that IDS as ETL improves the charge transfer and collection and simultaneously inhibits the charge recombination in the devices. Consequently, the optimal power conversion efficiency (PCE) of the device with IDS as ETL reaches up to 9.45%, with an open circuit voltage (V OC) of 0.80 V, a short circuit current density (J SC) of 16.88 mA cm−2 and a fill factor (FF) of 70.01%. This work provides a new approach to optimize the PCEs of the OSCs. [Display omitted] • A non-conjugated small molecule tetrasodium iminodisuccinate (IDS) have been successfully exploited in OSCs as ETL. • IDS modifies the active layer to exhibit a smoother interfacial morphology, which promotes the charge transport. • The device with IDS achieves the PCE of 9.45%, which is 57.23% efficiency improvement compared to the device without ETL. [ABSTRACT FROM AUTHOR]

Interface modification plays an important role in improving the efficiency of organic solar cells (OSCs). Here, disodium 4, 4'-(1,10-phenanthroline-4,7-diyl) dibenzenesulfonate (Phen-1) and disodium 4,7-diphenyl-1,10-phenanthroline 4′,4″-disulfonate (Phen-2) was successfully introduced into OSCs as cathode interface layers (CILs) using environment-friendly methanol as solvent. As contrasted with devices without (w/o) CILs, when Phen-2 as CIL, V OC of the devices increases from 0.73 V to 0.79 V, FF increases from 52.49% to 67.17%, respectively. Foremost, the power conversion efficiency (PCE) of the device has been improved from 5.56% to 8.58%. It was found that the surface of the active layer with CILs exhibited a smoother interface and better hydrophilicity, which facilitated the contact between the cathode and the active layer as well as the extraction and transport of electrons. This indicates that the use water-soluble phen series materials as CILs can improve device performance and provide an effective method for the preparation of environmentally friendly OSCs. [Display omitted] • Phenanthroline derivatives have been successfully exploited in OSCs as electron transport layer. • The electron transport layer of phenanthroline derivatives has high conductivity. • In the fullerene system, Phen-1 and Phen-2 achieved the PCE of 8.01% and 8.58%, respectively. [ABSTRACT FROM AUTHOR]

• The V 2 O 5 nanoparticles can fill the pinholes in PEDOT:PSS. • The hole transport layer of V 2 O 5 :PEDOT:PSS has high conductivity and hydrophobicity. • The crystallizability of the active layer is improved by adjusting the interface. • The PCE over 9.4% and FF over 70% can be achieved in OSCs with composite HTL. The fill factor (FF) as an important photovoltaic parameter is related to the property of transport layers and active layers for organic solar cells (OSCs). Herein, we propose a simple method to improve FF by using inorganic-organic composite hole transport layer (HTL) in OSCs. Through incorporating inorganic metal oxide, vanadium pentoxide (V 2 O 5) nanoparticles into PEDOT:PSS, the morphology and conductivity of the composite HTL are improved, due to V 2 O 5 nanoparticles can fill the pinholes in PEDOT:PSS and expose more PEDOT chains to the surface core–shell structure. The PTB7-Th:PC 71 BM-based OSCs with different HTLs were prepared. The power conversion efficiency and FF of the OSCs for the composite HTL can be greatly improved compared with the traditional HTL, which can reach up to 9.44% and 70.14%, respectively. The results of water contact angle and grazing incidence wide-angle X-ray scattering show that the hydrophobicity of the composite HTL is improved, which can not only improve the physical contact but also greatly affect the subsequent active layer formation, thus increasing the crystallinity of PTB7-Th:PC 71 BM. These results demonstrate that V 2 O 5 :PEDOT:PSS has good application prospects as a HTL to realize high-efficient OSCs. [ABSTRACT FROM AUTHOR]

The cathode modification is vital for improving device performance of polymer solar cells (PSCs). Here, N-(2-Carboxyethyl)iminodiacetic acid (C 7 H 11 NO 6) layers with different concentrations were deposited on the photoactive layer PTB7-Th:PC 71 BM film, and used as the cathode interface modification material for the conventional device structure of PSCs. By varying the concentration of C 7 H 11 NO 6 , the effect on the performance of PSCs was investigated. It was found that the efficiency of the photovoltaic device was reached as high as 8.86% at a C 7 H 11 NO 6 concentration of 1 mg mL−1, which was about 56% higher than the performance of the reference device. Among them, the C 7 H 11 NO 6 film acts as an effective cathode interface layers, forming an interfacial dipole on the surface of the PTB7-Th:PC 71 BM film to increase the built-in potential and promote photogenerated electron extraction and transport. [Display omitted] • Alcohol-Soluble C 7 H 11 NO 6 have been successfully exploited in PSCs as cathode interfacial layer (CIL). • C 7 H 11 NO 6 modifies the active layer to exhibit a smoother interfacial morphology. • The device with C 7 H 11 NO 6 as CIL achieves the PCE of 8.86%. [ABSTRACT FROM AUTHOR]

Interface modification makes an important contribution to improving the optoelectronic performance and stability of polymer solar cells (PSCs). Here, the hexamethylenetetramine (C 6 H 12 N 4) was successfully introduced into PSCs as cathode interface layers (CILs) using environmental-friendly methanol as solvent. Compared to the PSCs without CILs, the open circuit voltage (V OC) and short-circuit current density (J SC) of the device with C 6 H 12 N 4 CILs was increased from 0.44 V to 12.73 mA cm−2 to 0.77 V and 15.89 mA cm−2, respectively. More importantly, under the same experimental conditions, the optimal power conversion efficiency (PCE) of the device with C 6 H 12 N 4 CILs was improved to 7.79%, which is 185% higher than that of the device without C 6 H 12 N 4 CILs (2.73%). We found that the active layer PTB7-Th:PC 71 BM showed a smoother interface morphology and better hydrophilicity after insertion of CILs, which facilitated enhance the physical contact between active layers and cathode as well as electron extraction and transport. The results show that the introduction of C 6 H 12 N 4 as CILs provides an effective method for preparing high-performance PSCs. • C 6 H 12 N 4 has been successfully exploited in PSCs as electron transfer layer. • C 6 H 12 N 4 can reduce cathode work function and efficiently extract electrons. • C 6 H 12 N 4 modifies the active layer to exhibit a smoother interfacial topography, which reduces contact resistance of PSCs. [ABSTRACT FROM AUTHOR]