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Comprehensive Summary: The industrialization of organic solar cells (OSCs) faces challenges due to complex synthesis routes and high costs of organic photovoltaic materials. To address this, we designed and synthesized a series of polythiophene‐based donor materials, PTVT‐T‐xCl (20%Cl, 50%Cl and 100%Cl), by introducing different degrees of chlorine substitution within their conjugated skeletons. The incorporation of chlorine atoms does not change the planar conformation of the conjugated main chain of the control polymer, PTVT‐T, but effectively reduces their HOMO energy levels (≤ –5.3 eV) and alters the crystallinity of the polymers. In addition, when preparing OSC by blending with non‐fused electron acceptor A4T‐16, the non‐radiative energy loss of the three photovoltaic devices gradually decreased with the increase of chlorine content (0.343, 0.278 and 0.189 eV, respectively). Notably, PTVT‐T‐20%Cl exhibited a more moderate nanoscale phase separation with the acceptor, leading to efficient exciton dissociation, lower bimolecular recombination, and thus a favorable current in the OSCs. Consequently, the photovoltaic device based on PTVT‐T‐20%Cl:A4T‐16 achieved a remarkable photovoltaic efficiency of 11.8%. In addition, the PTVT‐T‐xCl series polymers show much lower material‐only‐cost (MOC) values than the other reported photoactive material systems. This work provides the way for the development of low‐cost photovoltaic materials and the industrial application of OSC, overcoming previous limitations posed by high energy losses in polythiophene‐based donors. [ABSTRACT FROM AUTHOR]

Interfacial defects between the organic–inorganic lead halide perovskite and hole‐transporting layers are one significant factor limiting the performance of the perovskite solar cells (PSCs). These defects typically result from either lead or halide atom vacancies or under‐coordinated Pb2+ atoms, which act as recombination centers for holes. To address this, it is demonstrated that a thin layer of a poly(bithiophene ester) (PBTE) or a poly(terthiophene diester) (PTTDE) introduced between the FA0.92MA0.08Pb(I0.92Br0.08)3 (MA+ = methylammonium; FA+ = formamidinium) perovskite and spiro‐OMeTAD hole transporting material (HTM) layers improves the device stability and power‐conversion efficiency (PCE). The PCE improvements are primarily associated with enhanced open‐circuit voltage and fill factor arising from Lewis‐base passivation of under‐coordinated Pb2+ through interaction with the polymer carbonyl groups, as well as enhanced charge transfer between the perovskite and HTM layers facilitated by the conjugated thiophene functionalities of the polymeric interlayer. Furthermore, the examined polymers improve the thermal and moisture stability of the devices. Encapsulated PSCs with PBTE and PTTDE retain 89 ± 1 and 94 ± 3% of their initial PCE after 1440 h at 65 °C under 0.5‐sun irradiation, respectively, while PSCs without a polymeric interlayer lose almost half of the performance. These results can guide future designs of polymeric interlayers for high‐performance PSCs. [ABSTRACT FROM AUTHOR]

The emerging solution‐based solar cells and photodetectors have gained worldwide research interest over the past decades. Hole transport materials (HTMs) have greatly advanced the progress of these solution‐based electronics. Nevertheless, developing low‐cost and efficient HTMs is far from satisfactory. In this contribution, poly(3‐pentylthiophene) (P3PT) is introduced as a facile, low‐cost, and versatile dopant‐free polymer HTM for both quantum dot (QD) and perovskite electronic devices. Compared to the broadly used poly(3‐hexylthiophene), P3PT presents the reduced molecular aggregation and preferential face‐on orientation, which can markedly enhance the hole‐carrier transport in optoelectronic devices. Accordingly, P3PT can deliver the substantial improvement of photovoltaic performance from ∼8.6% to ∼9.5% for QD/polythiophene solar cells and from ∼16% to ∼18.8% for perovskite/polythiophene solar cells, which are both among the topmost values in the corresponding fields. Furthermore, P3PT HTMs can also significantly enhance the photodetection performance of QD and perovskite photodetectors by a factor of ∼3, indicating its great application potential in a variety of emerging optoelectronics. [ABSTRACT FROM AUTHOR]

A new series of triphenylamine (TPA)‐functionalized isomeric polythiophenes are developed as hole transporting materials (HTM) for inverted tin‐based perovskite solar cells (TPSCs). Bithiophene (BT) is first functionalized with two TPA (electron donor; D) at 3 and 5 positions to give two structural isomeric compounds (3BT2D and 5BT2D). The functionalized BT2Ds are then coupled with 3,3′‐bis(tetradecylthio)‐2,2′‐bithiophene (SBT‐14)/3,3′‐ditetradecyl‐2,2′‐bithiophene (BT‐14) to produce structural isomeric polythiophenes (1‐4), which are compared to conventional poly[N,N″‐bis(4‐butylphenyl)‐N,N″‐bis(phenyl)‐benzidine] (poly‐TPD) as HTMs for TPSCs. With the appropriate alignment of energy levels with regard to the perovskite layer, the TPA‐functionalized polymers‐based TPSCs exhibit enhanced operational stability and efficiency. Moreover, the long thiotetradecyl chain in SBT‐14 with intramolecular S(alkyl)∙∙∙S(thio) interactions restricts the molecular rotation and has a strong impact on the molecular solubility and wettability of the film during device fabrication. Among all the polymers studied, TPSCs fabricated with 3‐SBT‐BT2D polymer exhibit the highest hole mobility as well as the slowest charge recombination and achieve the highest power conversion efficiency of 8.6%, with great long‐term stability for the performance retaining ≈90% of its initial values for shelf storage over 4000 h, which is the best efficiency for non‐PEDOT:PSS‐based TPSCs ever reported. [ABSTRACT FROM AUTHOR]

Polymerized small molecule acceptors have recently greatly facilitated the development of all‐polymer solar cells (All‐PSCs) with respect to the power conversion efficiencies (PCEs). However, high‐performance and low‐cost polymer donors for All‐PSCs are still lacking, limiting further large‐scale manufacturing of All‐PSCs. Herein, this work designs and synthesizes a new thiophene derivative, FETVT, featuring vinyl‐bridged fluorine and ester‐substituted monothiophene. Incorporation of FETVT into a polymer yields a high‐performance polythiophene derivative PFETVT‐T, which exhibits deep‐lying HOMO level, suitable solution pre‐aggregation ability, finely‐tuned polymer crystallinity, and appropriate thermodynamic miscibility with the polymer acceptor L15. As a result, binary based on PFETVT‐T achieves a record PCE of 11.81% with agood stability, representing a breakthrough for polythiophenes and their derivatives‐based All‐PSCs, which is also significantly higher than that (1.92%) of All‐PSCs based on its isomerized analog. Remarkably, PFETVT‐T achieves an impressive PCE exceeding 16% via the implementation of a ternary blend design. These findings offer a hopeful pathway toward attaining high‐performance, stable, and cost‐effective PSCs. [ABSTRACT FROM AUTHOR]

Three new ionic polythiophene derivatives, soluble in polar solvents, are synthesized with good yields using simple, low‐cost, and straightforward procedures. They are investigated as interfacial cationic conjugated polyelectrolyte (CPE) layers for halogen‐free bulk heterojunction polymeric solar cells, based on a water‐soluble electron‐donor polymer (poly[3‐(6‐diethanolaminohexyl)thiophene]) and a water‐soluble electron‐acceptor fullerene derivative (malonodiserinolamide fullerene). The simple insertion of the CPE interlayer between the active layer and the aluminum cathode dramatically increases the power conversion efficiency of the final device up to nearly 5%, resulting from a decrease of the electrode work function, improved electron extraction, and optimization of the morphology of the layers. The obtained results demonstrate that the incorporation of CPE layer is a powerful and convenient methodology for the development of highly efficient and eco‐friendly processable polymeric solar cells. [ABSTRACT FROM AUTHOR]

Interface properties between charge transport and perovskite light-absorbing layers have a significant impact on the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is a polyelectrolyte composite that is widely used as a hole transport layer (HTL) to facilitate hole transport from a perovskite layer to an anode. However, PEDOT:PSS must be modified using a functional additive because PSCs with a pristine PEDOT:PSS HTL do not exhibit a high PCE. Herein, we demonstrate an increase in the PCE of PSCs with a polyethylene glycol hexadecyl ether (Brij C10)-mixed PEDOT:PSS HTL. Photoelectron spectroscopy results show that the Brij C10 content becomes significantly high in the HTL surface composition with an increase in the Brij C10 concentration (0–5 wt%). The enhanced PSC performance, e.g., a PCE increase from 8.05 to 11.40%, is attributed to the reduction in non-radiative recombination at the interface between PEDOT:PSS and perovskite by the insulating Brij C10. These results indicate that the suppression of interface recombination is essential for attaining a high PCE for PSCs. [ABSTRACT FROM AUTHOR]

The electron donor poly-thienothiophene-benzodithiophene (PTB) polymer series displays remarkable properties that lead to more efficient bulk heterojunction (BHJ) organic solar cells. In this work, the ground and four excited states (bright S1 and dark S2–S4) of three different members of the PTBn (n = 1, 6, 7) series were studied and compared with the prototypical poly(3-hexylthiophene) (P3HT) donor polymer. Time-dependent density functional theory was employed to investigate oligomers of similar sizes (∼50 Å). Charge alternation electron accumulation and depletion regions of the four transitions are concentrated on the inner units, thereby favoring interaction with the electron acceptor in a BHJ. The bright S1 transition energies of PTBn are about 0.2 eV lower as compared to P3HT, thereby allowing a better match of their levels with the typical C60-type acceptor moiety in a BHJ. Side chains play a minor role in the electronic spectrum (less than ∼0.1 eV). The most efficient PTB7 transfers more electronic charge from its electron-rich benzodithiophene subunit to its electron-deficient thieno[3,4-b] thiophene subunit as compared to PTB1 and PTB6. We show that the dipolar effect, a partial concentration of negative and positive charges on the different parts of the donor polymer that favors charge separation, is more pronounced in PTBn polymers and typically an order of magnitude larger as compared to P3HT. These effects are conspicuous for the most efficient polymer of the series, PTB7, with its fluorine substituent shown to play a crucial role. [ABSTRACT FROM AUTHOR]

Hybrid solar cells with organic semiconductors and quantum dots (QDs) have witnessed great advance in the past few years. Nevertheless, the great majority of organic and QD hybrid solar cells generally employ halogenated solvents for the processing of organic hole‐transporting interlayers. Herein, the impact of solvents on the organic semiconductor material for hybird solar cells is systematically explored. The o‐xylene‐processed polythiophene delivers a champion photovoltaic performance of 8.7%, which is the record value for QD and poly(3‐hexylthiophene) (P3HT) hybrid solar cells. The morphology results reveal that P3HT films processed with o‐XY present the moderate morphology and characteristic length scales, enabling the high photovoltaic performance. Moreover, the relationships between solvents, molecular stacking, film morphology, and photovoltaic performance are built to offer the guideline of solvents screening for these hybrid solar cells. Moreover, the great superiority of nonhalogenated solvents in fabricating high‐performance optoelectronic devices with low hazards is demonstrated. [ABSTRACT FROM AUTHOR]

Four new conjugated polymers alternating benzothiadiazole units and thiophene moieties functionalized with ionic phosphonium or sulfonic acid salts in the side chains were synthesized by a postfunctionalization approach of polymeric precursors. The introduction of ionic groups makes the conjugated polymers soluble in water and/or polar solvents, allowing for the fabrication of bulk heterojunction (BHJ) solar cells using environmentally friendly conditions. All polymers were fully characterized by spectroscopic, thermal, electrochemical, X-ray diffraction, scanning electron, and atomic force techniques. BHJ solar cells were obtained from halogen-free solvents (i.e., ethanol and/or anisole) by blending the synthesized ionic push–pull polymers with a serinol-fullerene derivative or an ionic homopolymer acting as electron-acceptor (EA) or electron-donor (ED) counterparts, respectively. The device with the highest optical density and the smoothest surface of the active layer was the best-performing, showing a 4.76% photoconversion efficiency. [ABSTRACT FROM AUTHOR]

The emerging solution‐processed solar cells have attracted worldwide effort in the last decade. Developing efficient, stable, and cost‐effective solar cells is strongly desirable in countering the growing global warming. Nevertheless, the photovoltaic performance and stability of hybrid solar cells based on low‐cost polythiophenes are far from satisfactory, due to their high‐lying energy levels and excessive aggregation. Herein, it is shown that brominated polythiophene (P3HT‐Br), prepared via a facile two‐step approach can effectively facilitate charge transport and suppress recombination in quantum dot (QD)/organic heterojunctions. Accordingly, the power conversion efficiency of the optimized hybrid polythiophene/QD cell is boosted from 8.7% to 11% (a 26% increase) with markedly reduced energy loss. More strikingly, the device achieves record‐high thermal stability with a lifetime of over 400 h maintaining 80% of the initial performance. Both device efficiency and stability are the best reported for polythiophene/QD hybrid solar cells. Moving forward, brominated polythiophenes hold great application in perovskite solar cells with significantly improved performance and offer new opportunities for other emerging solar cells. [ABSTRACT FROM AUTHOR]

Polythiophenes (PTs) have attracted considerable interest for application in organic solar cells (OSCs) owing to their simple molecular structures and low‐cost synthesis. However, the power conversion efficiencies (PCEs) of PT‐based OSCs are lower than those of state‐of‐the‐art OSCs. Herein, the development of two sequentially fluorinated PT donors (PT‐2F and PT‐4F) is reported for realizing highly efficient OSCs. PT‐2F and PT‐4F are designed to contain two and four fluorine atoms, respectively, per repeating unit to decrease their highest occupied molecular orbital energy levels and increase the open‐circuit voltages of the OSCs. Importantly, the PT‐4F polymers exhibit high backbone rigidity and the desired temperature‐dependent aggregation behavior, affording well‐developed crystalline structures in thin films for efficient charge transport. These beneficial features promote the construction of an optimal blend morphology of PT‐4F:small‐molecule acceptor with a suitable energy offset and low energetic disorder. Thus, the PT‐4F‐based binary and ternary OSCs achieve high PCEs of 15.6% and 16.4%, respectively. [ABSTRACT FROM AUTHOR]

Polythiophenes (PTs) are promising electron donors in organic solar cells (OSCs) due to their simple structures and excellent synthetic scalability. However, the device performance of PT‐based OSCs is rather poor due mainly to large photon energy losses and an unfavorable active layer morphology. Herein, the authors report a new PT, which is abbreviated as P5TCN‐2F and features cyano‐group substituents for high‐efficiency OSCs. The cyano‐group endows P5TCN‐2F with a deep‐lying highest occupied molecular orbital energy level, which thereby contributed to high open‐circuit voltage in OSCs as a result of reduced non‐radiative recombination energy loss. Moreover, the cyano‐group leads to strong interchain interaction, improved polymer crystallinity, and appropriate miscibility with the prevailing non‐fullerene acceptors. Consequently, P5TCN‐2F offers over 15% power conversion efficiency when blended with various Y‐series non‐fullerene acceptors (Y6, Y6‐BO, eC9, and L8‐BO). Particularly, a champion efficiency of 16.1% is obtained by the P5TCN‐2F:Y6 blend, which is largely higher than that of any previous PT‐based OSCs. Moreover, the average figure of merit of the active layer based on P5TCN‐2F is much superior to that of benzodithiophene‐based polymers. These results suggest the renaissance of PT‐based OSCs and have opened an avenue to access high‐performance materials for the large‐scale production of OSC modules. [ABSTRACT FROM AUTHOR]

Summary: Improved film surface is a prerequisite to achieve high photovoltaic performance of inorganic perovskite solar cells because defective (under‐coordinated) lead ions derived from imperfect lattice structure of the film surface or grain boundaries the principal nonradiative recombination centers in the inorganic perovskite absorber. In this study, we suggest poly[3‐(4‐carboxybutyl)thiophene‐2,5‐diyl] (P3CT), a carboxylated p‐type conjugated polymer, as a passivating agent of the CsPbI2Br layer to tailor electronic properties of a perovskite absorber. With the P3CT passivation, the defective sites of the perovskite film surface were improved and stabilized, which can suppress nonradiative recombination to promote charge transport of CsPbI2Br‐based all‐inorganic perovskite solar cells. Consequently, the P3CT passivation delivers a power conversion efficiency (PCE) of 12.25% and decent long‐term stability of CsPbI2Br perovskite solar cells, which surpasses the pristine device without the passivation. The electricity generation capability under indoor light source of the passivated device is also studied, demonstrating a promising PCE of 27.47%. This work unveils the role of P3CT as a passivating agent to passivate the defective sites of CsPbI2Br perovskite film surface and grain boundaries, which facilitates charge transport and reduced carrier recombination of CsPbI2Br absorber in solar cell devices. [ABSTRACT FROM AUTHOR]

Conjugated polymers are encouraging substitute for creating clean and renewable energy for photoinduced charge generation and transport media in polymer solar cells (PSCs). Successful synthesis of a new solution processable n‐type polythiophene based π‐conjugated polymer (P3HT‐CN) is done where polythiophene units are substituted by cyano groups through post functionalization approach of synthesized P3HT which is cheap, stable, easily prepared, and inert against ambient conditions and is expected to be a competitive candidate for the acceptor material in non fullerene acceptors (NFAs) PSCs against fullerene derivative and used as the highly efficient active layer in the bulk heterojunction (BHJ) which increase the donor‐acceptor interfacial area through controlling the phase separation indicating device structure ITO/PEDOT:PSS/P3HT:P3HT‐CN/Al. Photovoltaic measurement of this PSCs device based on P3HT:P3HT‐CN demonstrate the PCE of 0.008% with an increased short circuit current density (Jsc) of 0.11 mA cm−2. The thermal, optical, and electrochemical properties are examined in detail showing high thermal stability, absorbance in the visible part of the solar spectrum, higher charge carrier mobility, and also mixed type corrosion inhibitive behavior with 90 and 78% inhibitor efficiency for P3HT and P3HT‐CN, respectively, built this class of material as smart which can be used for many other applications. [ABSTRACT FROM AUTHOR]

The photoelectric and optical characteristics of an organic solar cell (OSС) with a hole-transport layer based on a polyaniline complex and a photoactive layer with a bulk heterojunction based on P3HT polythiophene derivative and PC71BM fullerene have been studied. The results of modeling the optical properties of the functional layers and experimental measurements of the OSC characteristics enabled the optimal values of the thickness of the functional layers resulting in the maximum power conversion efficiency of the device to be identified. It has been determined that the hole-transport layer with a thickness of 30–60 nm, while having a transmission of more than 80%, effectively transferred holes to the photoanode from the photoactive layer, in which the exciton generation rate was 5.6–5.9 × 1016 cm–2 s–1. These values of the exciton generation rate at the maximum total light absorption in the device were provided by a photoactive layer with a thickness of 90–100 nm. [ABSTRACT FROM AUTHOR]

In the fabrication of inverted perovskite solar cells (PeSCs), it is necessary to select an appropriate p-type semiconductive material as hole transport layer (HTL), which will determine the crystallization quality of the subsequent perovskite films and hole charge extraction at the perovskite/HTL interface. Herein, a low-cost, low-temperature processed, and hydrophobic organic small molecule, N,N-bis(3-methylphenyl)-N,N-bis(phenyl) benzidine (TPD), is utilized as HTL in fabricating inverted PeSCs. It achieves a peak power conversion efficiency of 19.77% by optimizing the thickness, which is about 1.4 times higher than the PeSCs employing poly(3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT:PSS) as HTL. Compared with PEDOT:PSS-based PeSCs, the outstanding performance of PeSCs-based TPD derives from that of the employment of TPD as the HTL produced perovskite films with larger grain size and higher crystallinity. Owing to the hydrophobicity of TPD, TPD-based PeSCs exhibited longer stability. After storage of 700 h, the PeCE of TPD-based PeSCs retains 84.1%. [ABSTRACT FROM AUTHOR]

To lower the HOMO energy level of polythiophenes, carboxylate groups were introduced to the β-position of the thiophene unit, by which two polythiophenes with tetrathiophene (poly[5,5′′-(bis-3,3′′-((2-butyloctyl)-carboxylate)-2,2′:2′,2′′-terthiophene)-alt-5-thiophene], P-4T-2COOR) or pentathiophene (poly[5,5′′-(bis-3,3′′-((2-butyloctyl)-carboxylate)-2,2′:2′,2′′-terthiophene)-alt-5,5′-(2,2′-bithiophene)], P-5T-2COOR) repeating unit were synthesized. Absorption spectroscopy and cyclic voltammetry measurements revealed that the β-carboxylate substitution red-shifts the maximum absorption wavelength (λmaxabs) in solution owing to the electron accepting nature of the carboxylate group. In addition, the introduction of β-carboxylate reduces the HOMO level from -5.09 eV for P3HT to -5.34 eV and -5.18 eV for P-4T-2COOR and P-5T-2COOR, respectively, which is in good agreement with quantum chemisty calculation results. However, the β-carboxylate side chain showed different orientation to that of P3HT, which leads to weaker intermolecular π-π interaction as confirmed by less red-shited absorption in thin solid film and the quantum calculation results. Polymer solar cells using P-4T-2COOR and P-5T-2COOR as the electron donor, 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno‐[1,2‐b:5,6-b′]di‐thiophene (ITIC) as the electron acceptor were fabricated and tested. The P-4T-2COOR and P-5T-2COOR based cells showed high open circuit (VOC) of 0.73–0.99 V, significantly higher than that of P3HT based cell (VOC of 0.52 V), which can be ascribed to the lower HOMO energy levels and less condensed molecular packing of these two polymers. [ABSTRACT FROM AUTHOR]

Summary: High‐performance conjugated polymers for electronic applications can be developed by modulating an appropriate chemical structure that optimizes their crystal characteristics and charge‐transport behavior. Herein, we demonstrated the simultaneous enhancement of the in‐plane and out‐of‐plane charge transport of polythiophenes by random polymerization. We synthesized a polythiophene polymer by varying the ratio of two different dialkyl‐substituted bi‐thiophene and triethylene glycol‐substituted mono‐thiophene units; this polymer exhibited weakened orientation preferences of polymer crystallite films, a denser packing, and a more homogeneous surface morphology in comparison with its homopolymer analogue. Furthermore, this optimized random polymer afforded an enhanced in‐plane mobility of 7.72 cm2 V−1 second−1, measured by field‐effect transistor, and out‐of‐plane mobility of 8.86 × 10−4 cm2 V−1 second−1, measured by space‐charge‐limited‐current device. These are respectively 2.4 times and 10 times higher than the mobilities of the homopolymer (field‐effect mobility = 3.25 cm2 V−1 second−1 and space‐charge‐limited‐current mobility = 8.73 × 10−5 cm2 V−1 second−1). The enhanced charge transport in out‐of‐plane direction was also confirmed by fabricating perovskite solar cells using optimized polythiophene as a hole‐transporting material, which exhibited a higher efficiency of nearly 16.2% than the device with homopolymer analogue (12.0%). [ABSTRACT FROM AUTHOR]

Crystallinity and crystal orientation have a predominant impact on a materials' semiconducting properties, thus it is essential to manipulate the microstructure arrangements for desired semiconducting device performance. Here, ultra‐uniform hole‐transporting material (HTM) by self‐assembling COOH‐functionalized P3HT (P3HT‐COOH) is fabricated, on which near single crystal quality perovskite thin film can be grown. In particular, the self‐assembly approach facilitates the P3HT‐COOH molecules to form an ordered and homogeneous monolayer on top of the indium tin oxide (ITO) electrode facilitate the perovskite crystalline film growth with high quality and preferred orientations. After detailed spectroscopy and device characterizations, it is found that the carboxylic acid anchoring groups can down‐shift the work function and passivate the ITO surface, retarding the interface carrier recombination. As a result, the device made with the self‐assembled HTM show high open‐circuit voltage over 1.10 V and extend the lifetime over 4,300 h when storing at 30% relative humidity. Moreover, the cell works efficiently under much reduced light power, making it useful as power source under dim‐light conditions. The demonstration suggests a new facile way of fabricating monolayer HTM for high efficiency perovskite devices, as well as the interconnecting layer needed for tandem cell. [ABSTRACT FROM AUTHOR]

Organic polymer semiconductor‐based polymer solar cells (PSCs) are drawing tremendous research interest for their superior electrical, structural, optical, mechanical, and chemical properties. During the last two decades, immense efforts have been made toward the development of PSCs. Generally, poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is used as hole transport layer (HTL) of PSCs to improve hole extraction efficiency, but highly acidic PEDOT:PSS reduces device lifetime by destroying indium tin oxide (ITO) electrodes and active layers. To avoid this, some have attempted to develop inverted structured PSCs with different electron transport layers (ETLs); however, the power conversion efficiency (PCE) of these devices is limited owing to low electron mobility of their ETLs. Therefore, an attempt is made to improve the PCE of an inverted‐structured PSC by using indium gallium zinc oxide (IGZO) with optimized amount of indium (In), gallium (Ga), and zinc (Zn). Inverted PSCs with ZnO or IGZO (having various molar ratios of In, Ga, and Zn) as ETL with the structure ITO/ETL/PTB7:PC71BM/MoO3/Al are constructed. The PCE of the inverted PSC can be increased from 6.22% to 8.72% by using IGZO with an optimized weight ratio of In, Ga, and Zn as an ETL. [ABSTRACT FROM AUTHOR]

The p‐type conducting polymer poly (3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is widely utilized as the hole transport layer (HTL) for solution‐processed planar perovskite solar cells (PSCs) with a p‐i‐n structure. However, the inverted PSCs based on PEDOT:PSS HTL suffer from deficient open‐circuit voltage (VOC) and poor stability issues, because of the high electron affinity and acid nature of PEDOT:PSS. Herein, sodium benzenesulfonate (C6H5SO3Na) (SBS) is applied to modify the PEDOT:PSS (SBS–PEDOT:PSS) layer to form a smoother surface and better energy‐level alignment with the perovskite layer. In addition, the SBS–PEDOT:PSS layer with improved hole extraction capacity and suppressed charge recombination, significantly increases the grain size and crystallinity of the MA0.8FA0.2PbI3‐xClx perovskite film. Consequently, the power conversion efficiency (PCE) and VOC of the inverted PSCs are improved from 18.07% and 1.04 V to 19.41% and 1.08 V, respectively, after SBS modification. Moreover, the efficiency of the unencapsulated PSCs based on SBS–PEDOT:PSS remains above 90% after storing in ambient condition for 20 days. This research provides an accessible route to surmount the intrinsic imperfection of PEDOT:PSS and ameliorate the performance of PSCs. [ABSTRACT FROM AUTHOR]

Poly(3,4‐ethylenedioxythiophene) (PEDOT) is a very unique polymer. It can be very conductive, highly transparent, and environmentally stable. It is highly switchable between its oxidation state and neutral state. It forms a micellar complex with polystyrene sulfonate in aqueous conditions, and then can be solution‐processible and printable. Based on these advantages, PEDOT has been widely used as conductors and transparent electrodes in electronics and optoelectronics. The device performance is highly correlated with the structure and properties of PEDOT. In this review, advances in the synthesis, optoelectronic and chemical properties are comprehensively described and analyzed, as well as the strategies for tuning these properties to fulfill the requirement for device applications. Film processing techniques (printing and transfer printing) for the conducting polymer are also presented. Then, the applications of PEDOT as conductors for versatile organic and perovskite solar cells (single‐junction, tandem, semitransparent, colorful, flexible and ultraflexible, fully printed solar cells) are summarized. Finally future study directions for PEDOT in terms of conductivity enhancement and application‐oriented formulations are discussed. [ABSTRACT FROM AUTHOR]

Large‐area homogeneous and uniform perovskite films are key to the mass production of perovskite solar cells, especially the flexible ones. Different from the solution‐processed preparation, herein an all‐evaporation technique is developed for both perovskite films and the hole‐transporting layer in the modules. With the two‐step strategy of active‐layer design, homogeneous large‐area perovskite films are prepared via evaporation of first PbI2 and then CH3NH3I. An 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ)‐doped 4,4′,4″‐tris(N‐(aphthalene‐2‐yl)‐N‐phenylamino)triphenylamine (2T‐NATA) hybrid hole‐transporting layer is deposited on the indium‐tin‐oxide electrode via coevaporation. A power conversion efficiency (PCE) beyond 13% is achieved with the as‐prepared flexible perovskite solar module (active area of 16.0 cm2), which exhibits both higher stability and higher efficiency than the conventional solution‐processed module using poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS) as the hole‐transporting material. This novel strategy of all‐evaporation functional layers provides a feasible way for the industrialization of flexible perovskite solar cells. [ABSTRACT FROM AUTHOR]

• Degradation of a PTB7-Th:PC71BM-based OSC investigated by electrical measurements. • The charge carrier mobility showed only a minor change when exposed to ambient air. • The PCE loss was correlated to the bimolecular recombination coefficient increasement. • The variation of the reduction factor with the air exposure time was also obtained. The goal of this work is to make a contribution to the complex subject of organic solar cells degradation when operating in contact with ambient air. For this we built solar cells of the bulk heterojunction type composed of PTB7-Th (poly[4,8-bis(5-(2-ethylhexyl)thiophen-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)]) and PC71BM ([6,6]-Phenyl-C71-butyric acid methyl ester), respectively, as donor and acceptor materials of electrons. We present a series of current–voltage curves (J-V), both in the dark and under illumination, initially with the device immersed in an inert atmosphere and then exposing it to the ambient environment. J-V curves is then analyzed in terms of the Mott-Gurney equation, for measurements in dark, and by an analytical expression for the photocurrent, which allow us to check how the charge carrier mobility and the non-geminate recombination coefficient vary with time of exposure to air. We conclude that the charge carrier mobility (μ) for cells made with the PTB7-Th:PC 71 BM blend varies very little when in contact with air, and similar influence is observed on the recombination coefficient (k), since the Langevin coefficient reduction factor (ζ) is about 0.2 when the device is in inert atmosphere, reaching a value of almost 0.9 when exposed to air for 43 h. [ABSTRACT FROM AUTHOR]

Morphological and photovoltaic stabilities of poly(3‐hexylthiophene) (P3HT):phenyl‐C61‐butyric acid methyl ester (PC71BM) solar cells were investigated in pristine and modified states. To this end, four types of patterned/assembled nanostructures, namely reduced graphene oxide (rGO)‐g‐poly(3‐dodecylthiophene)/P3HT patched‐like pattern, rGO–polythiophene/P3HT/PC71BM nanofiber, rGO‐g‐P3HT/P3HT cake‐like pattern and supra(polyaniline (PANI)‐g‐rGO/P3HT), were designed on the basis of rGO and various conjugated polymers. Intermediately covered rGO nanosheets by P3HT crystals (supra(PANI‐g‐rGO/P3HT)) performed better than sparsely (patched‐like pattern) and fully (cake‐like pattern) covered ones in P3HT:PC71BM solar cell systems. Supra(PANI‐g‐rGO/P3HT) nanohybrids largely phase‐separated in active layers (root mean square = 0.88 nm) and also led to the highest performance (power conversion efficiency of 5.74%). The photovoltaic characteristics demonstrated decreasing trends during air aging for all devices, but with distinct slopes. The steepest decreasing plots were obtained for the unmodified P3HT:PC71BM devices (from 1.77% to 0.28%). The two supramolecules with the most ordered structures, that is, cake‐like pattern (10.12 mA cm−2, 51%, 0.58 V, 2.2 × 10−6 cm2 V−1 s−1, 4.3 × 10−5 cm2 V−1 s−1, 0.69 nm and 2.99%) and supra(PANI‐g‐rGO/P3HT) (12.51 mA cm−2, 57%, 0.63 V, 1.2 × 10−5 cm2 V−1 s−1, 3.4 × 10−4 cm2 V−1 s−1, 0.82 nm and 4.49%), strongly retained morphological and photovoltaic stabilities in P3HT:PC71BM devices after 1 month of air aging. According to the morphological, optical, photovoltaic and electrochemical results, the supra(PANI‐g‐rGO/P3HT) nanohybrid was the best candidate for stabilizing P3HT:PC71BM solar cells. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

A distannylated electron‐deficient bithiophene imide (BTI‐Tin) monomer was synthesized and polymerized with imide‐functionalized co‐units to afford homopolymer PBTI and copolymer P(BTI‐BTI2), both featuring an acceptor–acceptor backbone with high molecular weight. Both polymers exhibited excellent unipolar n‐type character in transistors with electron mobility up to 2.60 cm2 V−1 s−1. When applied as acceptor materials in all‐polymer solar cells, PBTI and P(BTI‐BTI2) achieved high power‐conversion efficiency (PCE) of 6.67 % and 8.61 %, respectively. The PCE (6.67 %) of polymer PBTI, synthesized from the distannylated monomer, is much higher than that (0.14 %) of the same polymer PBTI*, synthesized from typical dibrominated monomer. The 8.61 % PCE of copolymer P(BTI‐BTI2) is also higher than those (<1 %) of homopolymers synthesized from dibrominated monomers. The results demonstrate the success of BTI‐Tin for accessing n‐type polymers with greatly improved device performance. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is widely used as a hole transport materials in perovskite solar cells, due to a variety of suitable properties. However, the existence of the insulated PSS chain leads to the low electrical conductivity, which should be improved for the further development of inverted perovskite solar cells. In this study, three alcohol solvents were proposed for post-treatment of PEDOT:PSS thin films, which utilized the electrostatic shielding effect of alcohol molecules to promote phase separation of the PEDOT chain and the PSS chain. At the same time, The insulated PSS chain was removed by dissolving in highly hydrophilic alcohols. In the end, we successfully improved the conductivity of PEDOT:PSS thin films. By ethanol solvent treatment, the short-circuit current density of the perovskite solar cell based on glass/ITO/PEDOT:PSS was increased from 15.64 to 17.45 mA/cm2, the power conversion efficiency (PCE) reached 11.36%, which was 25% higher than the traditional structure. For flexible devices, a preliminary PCE of 9.20% was achieved. [ABSTRACT FROM AUTHOR]

Owing to low work functions of transparent anodes and poor contact issues at interfaces, p-i-n conductive metal oxide (CMO)-free perovskite solar cells (PVSCs) commonly suffer from a limited power conversion efficiency. Herein, we report an efficient CMO-free PVSC using poly(3-(4-methylamincarboxylbutyl)thiophene) (P3CT-N) modified poly(3,4-ethylenedioxylenethiophene):poly(styrenesulfonate) (PEDOT:PSS) anodes. The contact angle between PEDOT:PSS anodes and P3CT-N buffer layers tend to be 0° for an intimate contact. Meanwhile, the work function of the PEDOT:PSS anodes coated with P3CT-N is as high as −5.11 eV, which substantially accounted for the raised ability of hole transport. All the parameters (i.e. open-circuit voltage, short-circuit current density and fill factor) were improved simultaneously. As a result, the efficiency of the CMO-free solar cells was significantly improved from 4.63% to 13.13%. Our results indicate that P3CT-N is suitable to the highly conductive but hydrophobic PEDOT:PSS anodes for making high-efficiency CMO-free PVSCs. [ABSTRACT FROM AUTHOR]

Poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been is applied as hole transport material in organic electronic devices for more than 20 years. However, the redundant sulfonic acid group of PEDOT:PSS has often been overlooked. Herein, PEDOT:PSS‐DA is prepared via a facile doping of PEDOT:PSS with dopamine hydrochloride (DA·HCl) which reacts with the redundant sulfonic acid of PSS. The PEDOT:PSS‐DA film exhibits enhanced work function and conductivity compared to those of PEDOT:PSS. PEDOT:PSS‐DA‐based devices show a power conversion efficiency of 16.55% which is the highest in organic solar cells (OSCs) with (poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)‐4‐fluorothiophen‐2‐yl)benzo[1,2‐b:4,5‐b′]dithio‐phene))‐co‐(1,3‐di(5‐thiophene‐2‐yl)‐5,7‐bis(2‐ethylhexyl)‐benzo[1,2‐c:4,5‐c′]dithiophene‐4,8‐dione))] (PM6):(2,2′‐((2Z,2′Z)‐((12,13‐bis(2‐ethylhexyl)‐3,9‐diundecyl‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2′′,3′:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2‐g]thieno[2′,3′:4,5]thieno[3,2‐b]indole‐2,10‐diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile) (Y6) as the active layer. Furthermore, PEDOT:PSS‐DA also exhibits enhanced performance in three other donor/acceptor systems, exhibiting high compatibility in OSCs. This work demonstrates that doping PEDOT:PSS with various amino derivatives is a potentially efficient strategy to enhance the performance of PEDOT:PSS in organic electronic devices. [ABSTRACT FROM AUTHOR]

Recently, based on the tremendous progresses in performance of perovskite solar cells (PSCs), the inverted planar PSCs have attracted attentions for future applications. Since the traditional poly(3,4-ethylenedioxythiophene) hole transport layer could cause a loss of open-circuit voltage (Voc), some organic and inorganic alternatives have been widely investigated. However, the Voc is still below for the demand of optimized value. Here, we demonstrate that the reduced graphene oxide (RGO) doping is a facile and effective method to make molybdenum oxide (MoOx) as a promising hole transport layer (HTL) for high-performance PSCs. The conductive MoOx:RGO HTL can facilitate perovskite crystallization and reduce the potential losses of Voc in devices. Thus, a high PCE of up to 18.15% is achieved which simultaneously possesses a high Voc of 1.12 V. With this strategy, the MoOx:RGO provides a novel hole transport layer for high performance and decently stable optoelectronic devices. More importantly, it opens up the research significance of doping in inorganic buffer interlayers for the perovskite solar cells. [ABSTRACT FROM AUTHOR]

Poly(3‐thiophene ethanol) (P3ThEt)‐graft‐polystyrene (PSt) bottlebrushes were synthesized and applied in active layers of poly(3‐hexylthiophene) (P3HT):phenyl‐C71‐butyric acid methyl ester (PC71BM) solar cells as morphology compatibilizers. In the presence of 15 wt% of P3ThEt‐graft‐PSt bottlebrush compatibilizers, the P3HT crystallite dimensions (D(100) = 45.67 nm and D(020) = 30.12 nm) and Rmean (38.96 nm) of PCBM clusters were the largest and the layer spacings were all the smallest (d(100) = 1.054 nm, d(020) = 0.301 nm and d(PCBM) = 0.406 nm). These dimensional properties led to better hole (1.9 × 10−3 cm2 V−1 s−1) and electron (1.2 × 10−2 cm2 V−1 s−1) mobilities. The content of bottlebrushes was optimized at 15 wt%, and thereby the best photovoltaic results including the maximum cell efficiency of 5.37% were obtained for this turning point (12.75 mA cm−2, 61%, 0.69 V). On exceeding the optimum weight percentage, all photovoltaic parameters decreased markedly and reached even less than that of pristine devices (1.92% versus 2.24%). After an optimum weight percentage of compatibilizers, further enhancement in bottlebrush content in active layers saturated and finally oversaturated the system and, consequently, the cell parameters significantly decreased. Accumulation of bottlebrushes in interfaces and donor/acceptor phases ruined the system function even with large and packed P3HT crystallites and PC71BM clusters. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The performance of tandem organic solar cells (OSCs) is directly related to the functionality and reliability of the interconnecting layer (ICL). However, it is a challenge to develop a fully functional ICL for reliable and reproducible fabrication of solution‐processed tandem OSCs with minimized optical and electrical losses, in particular for being compatible with various state‐of‐the‐art photoactive materials. Although various ICLs have been developed to realize tandem OSCs with impressively high performance, their reliability, reproducibility, and generic applicability are rarely analyzed and reported so far, which restricts the progress and widespread adoption of tandem OSCs. In this work, a robust and fully functional ICL is developed by incorporating a hydrolyzed silane crosslinker, (3‐glycidyloxypropyl)trimethoxysilane (GOPS), into poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and its functionality for reliable and reproducible fabrication of tandem OSCs based on various photoactive materials is validated. The cross‐linked ICL can successfully protect the bottom active layer against penetration of high boiling point solvents during device fabrication, which widely broadens the solvent selection for processing photoactive materials with high quality and reliability, providing a great opportunity to continuously develop the tandem OSCs towards future large‐scale production and commercialization. [ABSTRACT FROM AUTHOR]

• Morphological, electrochemical, and photovoltaic stabilities of PBDT-DTNT:PC71BM solar cells were promoted. • Pre-designed supramolecules were utilized for stability increment. • The most stabilized devices were fabricated on the basis of rGO/PBDT-DTNT nanostructures. • The PCE decreased from 6.09% for upon-fabricated to 4.87% for 1 month aged systems. Morphological, electrochemical, and photovoltaic stabilities of the poly[benzodithiophene-bis(decyltetradecyl-thien) naphthothiadiazole] (PBDT-DTNT):phenyl-C61-butyric acid methyl ester (PC71BM) solar cells were promoted by the pre-designed supramolecules on the basis of reduced graphene oxide (rGO) nanosheets. Nanostructures consisted of the pristine rGO, grafted-rGO/PBDT-DTNT, rGO-polythiophene (GPTh) electrospun nanofiber, grafted-rGO/PBDT-DTNT electrospun nanofiber and rGO/PBDT-DTNT samples. The reduction in photovoltaic characteristics during air aging was the steepest for the unmodified PBDT-DTNT:PC71BM solar cells. From rGO based photovoltaics towards the rGO/PBDT-DTNT modified ones possessing the well-patterned PBDT-DTNT nanofibers, the slopes of graphs decreased. The most stabilized devices were fabricated on the basis of PBDT-DTNT:PC71BM:rGO/PBDT-DTNT active layers (power conversion efficiency (PCE) from 6.09% for upon-fabricated to 4.87% for 1 month aged systems) for having the most red-shifted and intensified absorbance, the largest phase separation, the lowest impedance responses and the highest photovoltaic characteristics during 1 month air aging (short circuit current density (J sc) of 12.09 mA/cm2, fill factor (FF) of 63%, open circuit voltage (V oc) of 0.64 V, hole mobility (µ h) of 5.3 × 10–5 cm2/V s, electron mobility (µ e) of 7.9 × 10–4 cm2/V s, charge transfer resistance (R tr) of 431 Ω cm2 and PCE of 4.87%). The GPTh/PBDT-DTNT/PC71BM (J sc = 10.31 mA/cm2, FF = 49%, V oc = 0.55 V, R tr = 796 Ω cm2 and PCE = 2.78%) and grafted-rGO/PBDT-DTNT/PBDT-DTNT (J sc = 10.98 mA/cm2, FF = 56%, V oc = 0.60 V, R tr = 539 Ω cm2 and PCE = 3.69%) electrospun nanofibers also imparted the stabilization of devices within 1 month. [ABSTRACT FROM AUTHOR]

Recently, Sn–Pb low‐bandgap (Eg) perovskite solar cells (PSCs) have attracted enormous interest as an ideal bottom cell for all‐perovskite tandem solar cells. However, due to the lack of high‐performance Sn–Pb low‐Eg PSCs, the development of all‐perovskite tandem solar cells is severely constrained. Herein, the performance of Sn–Pb low‐Eg (1.2 eV) PSC is improved significantly using diluted poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as a hole transport layer with a maximum power conversion efficiency (PCE) up to 19.58% and short‐circuit current density of 29.81 mA cm−2. The four‐terminal (4‐T) all‐perovskite tandem solar cell is constructed using an optical splitting system with this high‐efficient low‐Eg PSC as the bottom cell and a wide‐Eg (1.6 eV) PSC as the top cell. The best all‐perovskite 4‐T tandem solar cell shows a PCE of 23.26%. [ABSTRACT FROM AUTHOR]

Transparent poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) is widely used hole conducting material in optoelectronic devices. Secondary doping of PEDOT:PSS enables the tunability of its electronic properties. In this work, graphene oxide (GO) was used as a secondary dopant for PEDOT:PSS and the doped materials (composites) were tested for their efficiency as hole transport material in inverted bulk heterojunction (BHJ) solar cell. The composites were studied to unveil the effects of Coulombic interaction between GO and PEDOT:PSS where we note some segregation of PEDOT phase. We found that the GO majorly interacts with PSS through oxygeneous functional groups which promote the detachment of PEDOT from PSS and segregation of PEDOT. Electrochemical properties with and without illumination revealed some photo-induced changes to surface of the samples. Device performances showed about 2.2% efficiency enhancement when GO doping level was 0.25 (v:v) when compared to that of pristine PEDOT:PSS. [ABSTRACT FROM AUTHOR]

Three types of hole transport layers (HTLs) were developed based on multi-walled carbon nanotubes (CNTs), including pure CNT thin films, CNT:poly(3-thiophene ethanol) (P3ThEt)-g-polyaniline (PANI) nanocomposites, and CNT-g-poly(3-dodecyl thiophene) (PDDT):P3ThEt-g-PANI interconnected networks, and utilized in poly[benzodithiophene-bis(decyltetradecyl-thien) naphthothiadiazole] (PBDT-DTNT):phenyl-C61-butyric acid methyl ester (PC61BM) and poly[bis(triiso-propylsilylethynyl) benzodithiophene-bis(decyltetradecyl-thien) naphthobisthiadiazole] (PBDT-TIPS-DTNT-DT):PC61BM solar cells. Pure CNTs were not the appropriate candidates for application instead of conventional poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HTLs. To tackle this issue, the CNT:P3ThEt-g-PANI and CNT-g-PDDT:P3ThEt-g-PANI films were focused with thicknesses of 10 nm and 20 nm. The prominent characteristics peaked at 20-nm thin films of CNT-g-PDDT:P3ThEt-g-PANI, demonstrating the largest power conversion efficiencies (PCE) of 5.65 (12.84 mA/cm2, 62%, and 0.71 V) and 4.80% (11.59 mA/cm2, 60%, and 0.69 V) in the BDT-DTNT and PBDT-TIPS-DTNT-DT based devices, respectively. The CNT-g-PDDT:P3ThEt-g-PANI thin films which possess an interconnected network, composed of grafted-CNTs and P3ThEt-g-PANI bottlebrushes, were proper alternatives for conventional PEDOT:PSS HTLs and warranted the superior photovoltaic results by smooth morphologies (root mean square = 1.0–1.1 nm) and low sheet resistance (2.2–8.3 × 104 Ω/sq). The corresponding systems without grafting of CNT precursors were the second categories of well-functioned HTLs (3.13–4.04%) and had somehow decreased physical and photovoltaic properties. [ABSTRACT FROM AUTHOR]

We test the feasibility of using nanostructured electrodes in organic bulk heterojunction solar cells to improve their photovoltaic performance by enhancing their charge collection efficiency and thereby increasing the optimal active blend layer thickness. As a model system, small concentrations of single wall carbon nanotubes are added to blends of poly(3-hexylthiophene): [6,6]-phenyl-C61-butyric acid methyl ester in order to create networks of efficient hole conduction pathways in the device active layer without affecting the light absorption. The nanotube addition leads to a 22% increase in the optimal blend layer thickness from 90 nm to 110 nm, enhancing the short circuit current density and photovoltaic device efficiency by as much as ∼10%. The associated incident-photon-to-current conversion efficiency for the given thickness also increases by ∼10% uniformly across the device optical absorption spectrum, corroborating the enhanced charge carrier collection by nanostructured electrodes. [ABSTRACT FROM AUTHOR]

• Plasma treatment of solar cell for 1 min increased power conversion efficiency. • Plasma treatment reduces the defect densities in the heterojunction. • Reduction in the recombination processes due to plasma treatment. • Improves the SiNWs properties that improves the efficiency of the solar cell. Silicon Nanowires (SiNWs) can be easily synthesized by following the two-step electroless metal-assisted chemical etching method. These SiNWs are well known for their low reflectivity due to their excellent light-harvesting characteristics. In this paper, we demonstrated the effect of plasma treatment time on the performance of SiNWs solar cells. The 1 min plasma-treated SiNWs/Poly 3,4-[ethylene dioxy thiophene:Polystyrene sulfonate] (PEDOT׃PSS) solar cell showed increased power conversion efficiency than the untreated SiNWs/PEDOT׃PSS solar cell. The photo Current density-Voltage (J-V) analysis showed that the open circuit voltage (V O C) of the plasma treated solar cell for 1 min is higher (270 mV) than that of the untreated solar cell (120 mV). The increase in the value of V O C comes from different factors׃ one is due to the formation of a good interface between the SiNWs and PEDOT׃PSS layer; other is the reduction of defect densities in SiNWs/PEDOT׃PSS heterojunction, consequently the reduction in the recombination processes. Hence from this research, we found that by controlling the plasma treatment on SiNWs, it can improve the SiNWs properties which can further improve the efficiency of the solar cell. [ABSTRACT FROM AUTHOR]

The electrical and photovoltaic properties of organic Schottky and p–n type cells have been studied. Schottky devices are based on a spin-coated film of poly(3-butylthiophene) blend with the dye 1,3-bis-(dicyanomethylidene)-2-(4-dibutylaminobenzylidene)indane which is sandwiched between indium tin oxide (ITO) and gold electrodes. A depletion zone of 9.5 nm thick has been determined on a 220-nm-thick film. The conversion efficiency is equal to 0.01% under 100 mW cm-2 white light illumination. Effects of dye loading, film thickness, and light intensity are described. A model based on simple assumptions is used to fit the photoaction spectra. By evaporation under vacuum of a layer of N,N[sup ′]-dimethyl-3,4,9,10-perylenetetracarboxylic diimide between the ITO and the polymer film, we have fabricated hybrid polymer-molecular p–n type photovoltaic cells. The role of this molecule in the photogeneration has been studied. A constant power conversion efficiency of 0.15% has been measured under white light illumination between 0.2 and 200 mW cm-2. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Core–mantle–shell supramolecules composed of carbon nanotube (CNT)-graft-polyaniline (PANI), poly(3-hexylthiophene) (P3HT), and poly[benzodithiophene-bis(decyltetradecyl-thien) naphthothiadiazole] (PBDT-DTNT) precursors were designed and utilized in PBDT-DTNT:phenyl-C61-butyric acid methyl ester (PC61BM) solar cells. Weight ratio of polymer:CNT-graft-PANI was 9:1 and the weight ratios were 1:1 in binary and 1:1:1 in ternary systems. Diameters of core(CNT)–mantle(PANI), core(CNT)–mantle(PANI)–shell(P3HT), and core(CNT)–mantle(PANI)–shell(PBDT-DTNT) nanostructures ranged in 75–90 nm, 145–160 nm, and 120–130 nm, respectively. Efficacies of 6.82% (13.92 mA/cm2, 0.71 V, 69%, 7.1 × 10−3 cm2/V s and 1.9 × 10−2 cm2/V s) and 7.60% (14.66 mA/cm2, 0.73 V, 71%, 9.0 × 10−3 cm2/V s and 3.4 × 10−2 cm2/V s) were acquired for photovoltaics based on the nanostructures having PBDT-DTNT and P3HT shells, respectively. The PANI mantle may act as both acceptor (accepting the electrons from core) and donor (donating the electrons to shell) in the configuration of core–mantle–shell supramolecules. The P3HT shells acted better than the PBDT-DTNT ones, originated from the simple structure of P3HT backbones and their more ordered and thicker shells, and thus had larger charge mobilities and currents. [ABSTRACT FROM AUTHOR]

A new p-type electrode buffer layer (EBL) material was developed by the networks composed of multi-walled CNTs (MWCNTs) and poly(3-thiophene ethanol) (P3ThEt)-g-polyaniline (PANI) bottlebrush copolymers. The nanocomposites of CNT:P3ThEt-g-PANI were prepared in three different thicknesses (5, 15, and 25 nm) and employed as hole transport layer (HTL) in poly(3-hexylthiophene) (P3HT):phenyl-C71-butyric acid methyl ester (PC71BM) solar cells. A trade-off was detected between the sheet resistance and transmittance by elevating the HTL thickness for both pure CNT and CNT:P3ThEt-g-PANI nanocomposites. The CNT:P3ThEt-g-PANI thin films, in particular with an optimal thickness of 15 nm, were the turning points for equilibrating the film thickness, transmittance, surface roughness, and sheet resistance values. The smoothest thin films of CNT:P3ThEt-g-PANI with the thickness of 15 nm, the transmittance of 85–89%, and the sheet resistance of 5.6 × 104 Ω/sq reflected the best results of 12.85 mA/cm2, 60.7%, and 0.68 V. Hence, a maximum power conversion efficiency (PCE) of 5.30% was acquired among all solar cells fabricated in current work. After peaking at 15 nm, the second group of proper results was recognized in CNT:P3ThEt-g-PANI (25 nm)/P3HT:PC71BM photovoltaics (10.37 mA/cm2, 49.0%, and 0.62 V). The PCE of 3.15% for this system was even greater than the ideal performance (= 2.94%) detected in the pure CNT (15 nm)/P3HT:PC71BM solar cells. [ABSTRACT FROM AUTHOR]

The synthesis, characterisation and application as electron-acceptors in organic photovoltaic cells of new [1,2,5]thiadiazolo[3,4-g]quinoxaline-based small molecules with oligo(ethylene oxide) solubilising groups and tunable optical bandgaps are reported. A new p-type polymer consisting of a polythiophene derivative substituted with analogous solubilising groups was also synthesised to perform as a donor, in combination with the small molecules, for bulk-heterojunction solar cells using ethanol/anisole mixtures as low toxic solvents to process the active blends. Comparison of the structural, electrochemical and photophysical properties of the small molecules elucidated on the structural dependence of their optical bandgaps, ranging from 1.31 to 2.25 eV. The active layers composed of the polythiophene donor and the small molecules showed well-intermixed morphologies, and the best performing blends showed a fibrillar-type morphology, indicative of more ordered molecular packings. Blends processed from the 50 : 50 (v/v) mixture of ethanol and a low toxic solvent, anisole, yielded low power conversion efficiencies of 0.39% in non-optimized organic solar cells. Although the efficiencies are low, these are the first reported results of OSCs with active layers composed of non-fullerene acceptors processed from ethanol-based solvent formulations. This study provides guidelines for the design of non-fullerene acceptors for the fabrication of OSCs processed from environmentally friendly solvents. [ABSTRACT FROM AUTHOR]

Perovskite solar cells have emerged as one of the most promising next-generation photovoltaic technologies and have achieved a record power conversion efficiency of 22.7%. The technology meets industrial demands for cost effectiveness and scalability; however, the instability of lead halide perovskites toward moisture is a major barrier to their commercial development. Previous studies have revealed that the use of hydrophobic hole-transport layers (e.g., poly(3-hexylthiophene), P3HT) can slow the ingress of water vapor and improve the lifetime of the underlying perovskite, suggesting a route to longer lived devices. In this work, we report the synthesis of a variety of poly(3-alkoxythiophenes) with different side chains. The side chains range from hydrophilic (triethylene glycol methyl ether) to extremely hydrophobic (highly fluorinated hexyloxy). We evaluated the polymers, alongside commercially available P3HT, for their ability to stabilize methylammonium lead iodide films at high relative humidities. The fluorinated polythiophenes were able to substantially improve the perovskite lifetime, suggesting that more hydrophobic hole-transport layers may be a route to more stable perovskite solar cells. [ABSTRACT FROM AUTHOR]

Abstract Charge-transport materials for use in highly efficient and stable perovskite solar cells (PSCs) must exhibit energy levels appropriate for high charge selectivity, sufficiently high charge-transport ability for efficient charge collection, and high humidity resistance for long-term device stability. Polythiophenes are a promising class of hole-transport layer (HTL) materials that could satisfy these requirements. However, PSCs fabricated using conventional poly(3-hexylthiophene) (P3HT) HTLs show limited efficiencies of <16% owing to the shallow highest occupied molecular orbital (HOMO) energy level and poor charge extraction ability of P3HT. Herein, we demonstrate that the fluorinated polythiophene derivative FEH is a suitable replacement for P3HT and a promising HTL material for perovskite solar cells. The FEH was found to have a deeper HOMO and exhibit more efficient charge-extraction ability at the perovskite/HTL interface than P3HT. This is attributed to the electron-withdrawing nature of the fluorine atoms in FEH and its ability to form more uniform films on the perovskite layer. Thus, when FEH was employed as the HTL, the corresponding PSC showed an improved efficiency of 18.0% and an enhancement of all device parameters compared with control devices fabricated using P3HT (10.8%) and Spiro-OMeTAD (17.0%) HTLs. Moreover, fluorination on the conjugated backbone of the polymer increases its hydrophobicity, and the resulting hydrophobic surface of the FEH HTL prevents the ingress of water, resulting in an improvement of the long-term stability of the corresponding PSCs under air exposure. Graphical abstract Image 1 Highlights • Fluorinated polythiophene derivative was used as hole-transport layer (HTL) of perovskite solar cells (PSCs). • The fluorinated polymeric HTL shows efficient charge extraction and hydrophobic surface property. • The PSCs based on the HTL exhibit a best efficiency of 18.0% and better stability compared to conventional Spiro-OMeTAD HTL. [ABSTRACT FROM AUTHOR]

Abstract Poly (3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) doped with Eu3+ is spray deposited for creating an Anode buffer layer (ABL). The doping of Eu3+ in PEDOT:PSS causes the down-shifting of the UV light to visible spectrum enhancing the photon concentration in this region. The use of electric field during the spray deposition of undoped and Eu3+ doped PEDOT:PSS film improved the surface morphology and the electrical conductivity, which help to improve the solar cell performance. The organic solar cell (ITO/ABL/PTB7:PC 71 BM/Al) fabricated using the electric field assisted spray deposited Eu3+ doped PEDOT:PSS ABL is shown improvement in the power conversion efficiency in comparison to the device fabricated using undoped PEDOT:PSS without electric field. This enhancement in the efficiency of the device in terms of current density and Fill factor can be attributed to an increase in the photon concentration in visible region due to the downshifting and improvement in the surface morphology and conductivity due to applied electric field during deposition. Graphical abstract Image 106492 Highlights • Downshifting process in Eu3+ doped organic solar cell. • Effect of electric field on devices. • Enhancement in the conductivity and PEC of OSCs. [ABSTRACT FROM AUTHOR]

Abstract The high stability and strong coupling nature of gold nanoparticles (Au-NPs) than other metal counter parts have attracted the solar cell industry to pursue enhanced performances. Herein, we report on the improved performance of polymer bulk hetero-junction (BHJ) solar cells by the incorporation of large-size Au-NPs in the hole transport layer of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). To examine the reproducibility of the enhancement parameters, two different donor photoactive materials have been adapted and the role of larger-size (>70 nm, i.e. 71, 80, 87, 103 nm) Au-NPs in BHJ solar cells have been studied extensively. Significantly, when employing Au-NPs smaller than 80 nm, near-field coupling (localized surface plasmon resonance; LSPR) was prevalent, while the infusion of Au-NPs with sizes greater than 87 nm resulted in far-field scattering enhancement as the dominant effect, which was clearly determined using time resolved photo luminescence studies. The superior power conversion efficiency of 5.35% and 8.58% was achieved with PBDTTT-C: PC 61 BM and PTB7: PC 71 BM BHJs respectively, by employing 87 nm Au-NPs due to the balanced contribution of near- and far-field plasmonic effects, improved vertical coverage and better interfacial properties. This study illustrates that 87 nm Au-NPs is the maximum size to attain the improved efficiency, above which the rate of enhancement reduces dramatically. Graphical abstract Image 1 Highlights • Plasmonic enhancement in organic solar cells by gold nanoparticles (Au-NPs). • Au-NPs with 71 and 80 nm shows dominant near-field enhancement. • Au-NPs with 87 and 103 nm shows dominant far-field scattering enhancement. • Improved vertical coverage and work function also reason for improved performances. • 87 nm Au-NPs demonstrated the optimum condition of near- and far-field enhancements. [ABSTRACT FROM AUTHOR]