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In this paper, we present new organics chemical structures of pendant phenyl ester -substituted thiophene and benzothiadiazole based copolymers leading to donor (D)-acceptor (A) structure-types. Geometrics and photo-physical properties of the studied chemical structure are exploited in the further ground and excited -state. Theoretically, using the DFT and TD-DFT quantum chemical calculation implanted in Gaussian09 software, geometrical and electronic parameters such as the energy of HOMO and LUMO level, the Egap= EHomo - ELumo and focused electronic parameters of the molecules were determined. The studied molecules show good photovoltaic properties. Thus, the studied chemical structures are blended with acceptor compounds such as fullerene and PCBM derivatives in the bulk-heterojunction solar cell. Quantic chemical calculations show that the studied compound present good electronic, optical, and photovoltaic properties and can be used as potential electron donors in organic solar cells Heterojunction (BHJ).

The poisoning potential of lead, which is the main component of the absorber layer of lead halide (Pb) perovskites, as well as the stability problems of the manufactured devices, constitute a major obstacle to the industrialization of this technology. As a result, recent research is concentrating on lead-free metal halide perovskites. Unfortunately, current lead-free perovskites suffer from poor performance, hence the interest of our study. The research presented here shows that optimizing several variables related to the performance of each layer of a perovskite solar cell (PSC) constructed from lead-free inorganic materials provides an efficiency of 18.13%. We designed a structure with outstanding performance using the FTO/PC _60 BM/CsSn _0.5 Ge _0.5 I _3 /Spiro-OMeTAD/Au configuration. The impact of various relevant factors, such as the thickness and defect density of the absorber layer their doping densities, the back contact work, and the operating temperature, have been thoroughly investigated to boost the performance of the proposed device. The performance of cesium-tin-germanium triiodide (CsSn _0.5 Ge _0.5 I _3 ) solar cells with different electron transport materials, including ZnO, TiO _2 , CdS, C _60 ; Cd _0.5 Zn _0.5 S, IGZO, has also been examined. It has been demonstrated that using ZnO as an electron transport layer improves electron extraction and, therefore, performance. The best outcomes are obtained after optimizing all the factors mentioned above, namely: Jsc of 28.70 mA/cm ^2 , Voc of 1.115 V, FF of 87.86%, and PCE of 18.13%. Additionally, the explored structure may be an excellent candidate for the future development of lead-free perovskite solar cells.

The power conversion efficiency of inorganic–organic hybrid lead halide perovskite solar cells (PSCs) is approaching that of those made from single crystalline silicon; however, they still experience problems such as hysteresis and photo/electrical‐field‐induced degradation. Evidences consistently show that ionic migration is critical for these detrimental behaviors, but direct in‐situ studies are still lacking to elucidate the respective kinetics. Three different PSCs incorporating phenyl‐C61‐butyric acid methyl ester (PCBM) and a polymerized form (PPCBM) is fabricated to clarify the function of fullerenes towards ionic migration in perovskites: 1) single perovskite layer, 2) perovskite/PCBM bilayer, 3) perovskite/PPCBM bilayer, where the fullerene molecules are covalently linked to a polymer backbone impeding fullerene inter‐diffusion. By employing wide‐field photoluminescence imaging microscopy, the migration of iodine ions/vacancies under an external electrical field is studied. The polymerized PPCBM layer barely suppresses ionic migration, whereas PCBM readily does. Temperature‐dependent chronoamperometric measurements demonstrate the reduction of activation energy with the aid of PCBM and X‐ray photoemission spectroscopy (XPS) measurements show that PCBM molecules are viable to diffuse into the perovskite layer and passivate iodine related defects. This passivation significantly reduces iodine ions/vacancies, leading to a reduction of built‐in field modulation and interfacial barriers. [ABSTRACT FROM AUTHOR]

Blends of semiconducting (SC) and ferroelectric (FE) polymers have been proposed for applications in resistive memories and organic photovoltaics (OPV). For OPV, the rationale is that the local electric field associated with the dipoles in a blend could aid exciton dissociation, thus improving power conversion efficiency. However, FE polymers either require solvents or processing steps that are incompatible with those required for SC polymers. To overcome this limitation, SC (poly(3‐hexylthiophene)) and FE (poly(vinylidene fluoride‐trifluoroethylene)) components are incorporated into a block copolymer and thus a path to a facile fabrication of smooth thin films from suitably chosen solvents is achieved. In this work, the photophysical properties and device performance of organic solar cells containing the aforementioned block copolymer consisting of poly(vinylidene fluoride‐trifluoroethylene): P(VDF‐TrFE), poly(3‐hexylthiophene): P3HT and the electron acceptor phenyl‐C61‐butyric acid methyl ester: [60]PCBM are explored. A decrease in photovoltaic performance is observed in blends of the copolymer with P3HT:[60]PCBM, which is attributed to a less favorable nanomorphology upon addition of the copolymer. The role of lithium fluoride (the cathode modification layer) is also clarified in devices containing the copolymer, and it is demonstrated that ferroelectric compensation prevents the ferroelectricity of the copolymer from improving photovoltaic performance in SC‐FE blends. [ABSTRACT FROM AUTHOR]

This study aims to evaluate the characteristics of novel organic D-π-A-π-D class small-molecules by using carefully the density functional theory, and time-dependent density functional theory calculations. Thedesigned sequence of (D-A) BHJ-1a to BHJ-4a in organic Bulk Heterojunction (BHJ) solar cells has been comprehensively analysed. Thiéno[2,3-b]indole (TI) has been used as donor, and Diketopyrrolopyrrole (DPP) as acceptor for all compounds. In order to improve the electronic, photovoltaic, and opticalproperties, we have substituted thiophene unit with furan, thieno[2,3-b]thiophene, thiazole and thiazolothiazole as π-bridge moieties. Thus, the result shows that the wise choice of the π-bridge units plays a significant role in improving Egap, producing a high bathochromic shift, and increasing VOC as well as a theoretical power conversion efficiency (PCE) over 7%. Interestingly, BHJ-4a with suitable π-bridge presents the optimal electronic properties with low band gap (1.870 eV) and high VOC (1.534 eV). Furthermore, we have modelled a Bulk heterojunction organic photovoltaic cells based on donor-PCBM complex in order to achieve the optimum Egap and VOC. Consequently, the obtained results provide a new way to design BHJ small molecule donors with higher power conversion efficiency. [ABSTRACT FROM AUTHOR]

Poly (3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) are commonly used for the fabrication of organic photovoltaics (OPV). Efficiency limitations of OPVs could be circumvented by incorporation of inorganic nanostructures into organic blends. Again, integration of organic solar cells with well-developed silicon photovoltaic technology is ultimately desirable. In the present work, GaN nanowires with diameters of 25–50 nm and two lengths (200 and 500 nm) have been grown using molecular beam epitaxy technique. Solar-grade monocrystalline silicon wafers were used as substrates for nanowire synthesis. GaN nanostructures were incorporated into P3HT:PCBM photoactive layer in order to facilitate charge transfer between P3HT:PCBM and Si. Samples with and without nanowires were compared. Addition of nanowires led to the improvement in photovoltaic performance. Open circuit voltage has risen by 72% and short circuit current density by 200%. Series resistance has decreased 50 times, and power conversion efficiency has risen 20.7 times. Additional maxima are found in photocurrent spectrum corresponding to carriers being generated near GaN absorption edge. Moreover, external quantum efficiency peaks near GaN absorption edge, indicating the formation of current transfer channel via P3HT/GaN/Si cascade heterojunction. Mechanism explaining source of abovementioned improvement is proposed. [ABSTRACT FROM AUTHOR]

The application of carbon nanotubes in electronic devices requires detailed knowledge of their electrical properties. Herein, the long‐lasting electric field‐induced polarization of single‐wall carbon nanotube (SWCNT) networks is demonstrated. It is found that electric voltage applied to the films of SWCNTs and their blends with [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) creates persistent polarization that partly screens the external electric field and creates a built‐in electric field of the opposite direction remaining for several days. The built‐in electric field has caused the appearance of an open‐circuit photovoltage and a short‐circuit photocurrent under the sample illumination at zero applied voltage. The built‐in field showed a clearly bicomponential decay. The short tens of microseconds component is attributed to the electronic polarization, while the long‐lived component, which decreases at low temperatures, is attributed to the temperature‐assisted motion of ions. [ABSTRACT FROM AUTHOR]

Organic bulk heterojunction photovoltaics, merely incorporating monoadducts of cyclopenteno[60]fullerenes (CPFs) as n‐type materials and P3HT as p‐type materials, display superior power conversion efficiency up to 4.6 ± 0.12%, superseding that with PC61BM/P3HT (3.8 ± 0.20%) for ca. 20%, under AM 1.5G irradiation―primarily attributed to the lack of homo‐conjugation on CPFs and their higher LUMO energy levels. [ABSTRACT FROM AUTHOR]

Tinted and colour-neutral semitransparent organic photovoltaic elements are of interest for building-integrated applications in windows, on glass roofs or on facades. We demonstrate a semitransparent organic photovoltaic cell with a dry-laminated top electrode that achieves a uniform average visible transmittance of 51% and a power conversion efficiency of 3%. The photo-active material is based on a majority blend composed of a visibly absorbing donor polymer and a fullerene acceptor, to which a selective near-infrared absorbing cyanine dye is added as a minority component. Our results show that organic ternary blends are attractive for the fabrication of semitransparent solar cells in general, because a guest component with a complementary absorption can compensate for the inevitably reduced current generation capability of a high-performing binary blend when applied as a thin, semitransparent film.

[Display omitted] This work reports the self-assembly between [6,6]-phenyl C 71 butyric acid methyl ester (PCBM) and 2,3,7,8,12,13,17,18-octaethyl-21H,23H porphyrin (1)(and/2,3,7,8,12,13,17,18-octaethyl-21H,23H porphyrin Zn(II) (2) in toluene. Ground state intermolecular interaction is evidenced from absorption spectrophotometric measurements. New absorption bands are observed in the visible region which may be identified due to charge transfer (CT). Several important physicochemical factors are enumerated for PCBM- 1 and PCBM- 2 systems. Fluorescence investigations elicit complex formation of PCBM with porphyrins (with both 1 and 2) and reveal considerable magnitude of binding constant (K) for PCBM- 2 system, i.e., K PCBM- 2 = 80,435 dm3⋅mol−1 compared to PCBM- 1 system, i.e., K PC M- 1 = 12,600 dm3·mol-1 as well as highly ratio of selectivity in binding (K PCBM- 2 /K PCBM- 1 ∼ 6.4). Time resolved fluorescence experiments reveal that photoexcited decay from the excited singlet state of porphyrins (i.e., 1 * and 2 *) by PCBM is statically controlled compared to dynamic path. Magnitude of solvent reorganization energy indicates possibility of faster charge recombination in case of PCBM- 2 system. Both 1H and 13C NMR measurements provide substantial support behind complexation of PCBM with porphyrins (both 1 and 2) in solution. Ab initio calculations in vacuo support the trend in K for PCBM- 1 and PCBM- 2 systems and establish the proper orientation of PCBM towards 1 (and/ 2) during complexation. Transient absorption measurements establish two different mode of energy transfer pathway from porphyrin to PCBM in toluene. [ABSTRACT FROM AUTHOR]

With the aim of determining the best input geometry for DFT calculations of [60]PCBM, the geometry of 24 chemically possible [60]PCBM conformers were optimised and their electronic energies and average bond strains were determined. A DFT analysis of the relevant dihedral angles provided insights into the dynamical behaviour of the ester group through sterically restricted bond rotations. In addition, the 13C NMR spectra of the six better performing conformers were simulated and compared with an experiment. There is a close correlation between average bond strain, total electronic energy and mean absolute error of the simulated 13C NMR spectra of the ester carbons. The best overall candidate conformer for the input geometry had the C61-C4, C4-C3 and C3-C2 single bonds of the alkyl chain in syn, anti and anti arrangements, respectively, and had the C2-C1 and C1-O single bonds of the ester in syn and anti arrangements, respectively. This contrasts strikingly with most representations of PCBM in the literature, which depict all relevant bonds in anti arrangements.

[Display omitted] Organic field-effect transistors with styryl fullerene as a semi conductor layer applied by centrifugation are considered. Electron mobility in the transistors was 0.067 ± 10% cm2 V−1 s−1, whereas the mobility of electrons in these devices after the vacuum deposition of a semiconductor layer was much lower (0.023 ± 10% cm2 V−1 s−1). [ABSTRACT FROM AUTHOR]

Hybrid polymer solar cell has privilege than its conventional structure, where it usually has structure of (ITO/PEDOT:PSS/Active Layer/Al). In humid environment the PEDOT:PSS will absorb water and hence can easily etch the ITO. Therefore it is necessary to use an alternative method to avoid this drawback and obtain more stable polymer solar cells, namely by using hybrid polymer solar cells structure with an inverted device architecture from the conventional, by reversing the nature of charge collection. In this paper we report the results of the fabrication of inverted bulk heterojunction polymer solar cells based on P3HT:PCBM as active layer, utilizing ZnO interlayer as buffer layer between the ITO and active layer with a stacked structure of ITO/ZnO/P3HT:PCBM/PEDOT:PSS/Ag. The ZnO interlayer is formed through short route, i.e. by dissolving ZnO nanoparticles powder in chloroform-methanol solvent blend rather than by sol-gel process. Based on the measurement results on electrical characteristics of inverted polymer solar cells under 500 W/m2 illumination and AM 1.5 direct filter at room temperature, cell with annealing process of active layer at 110 °C for 10 minutes results in higher cell performance than without annealing, with an open-circuit voltage of 0.21 volt, a short-circuit current density of 1.33 mA/cm2 , a fill factor of 43.1%, and a power conversion efficiency of 0.22%. The low cell’s performance is caused by very rough surface of ZnO interlayer.

We have successfully functionalized multiwalled carbon nanotubes (MWCNTs) using nitrene approach employing the two aryl azides as a precursor for nitrene generation. The dispersion of functionalized MWCNTs has been enhanced in various organic solvents. These functionalized MWCNTs have been successfully doped in various concentrations in the bulk heterojunction (BHJ) organic photovoltaic (OPV) cells with a poly (3-hexyl thiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) photoactive blended layer. The incorporation of MWCNTs with aryl functional groups, in active the layer, results in enhanced performance with respect to a reference cell. The maximum power conversion efficiency of 1.86% is achieved with adduct I while in the case of adduct II it gets double to 2.0% in comparison with a reference cell. This improvement in the device performance is attributed to enhanced exciton dissociation and improved charge transport properties due to the formation of a nanotube percolation network in the photoactive composite layer.

Polymer-based organic solar cells are of great interest as they can be produced with low-cost techniques and also have many interesting features such as flexibility, graded transparency, easy integration, and lightness. However, conventional wide bandgap polymers used for the light-absorbing layer significantly affect the power conversion efficiency of organic solar cells because they collect sunlight in a given spectrum range and due to their limited stability. Therefore, in this study, polymers with different bandgaps were used, which could allow for the production of more stable and efficient organic solar cells: P3HT as the wide bandgap polymer, and PTB7 and PCDTBT as low bandgap polymers. These polymers with different bandgaps were combined with PCBM to obtain increased efficiency and optimum photoactive layer in the organic solar cell. The obtained devices were characterized by measuring optical, photoelectrical, and morphological properties. Solar cells using the PTB7 and PCDTBT polymers had more rough surfaces than the reference cell using P3HT. The use of low-bandgap polymers improved Isc significantly, and when combined with P3HT, a higher Voc was obtained. [ABSTRACT FROM AUTHOR]

Herein, a post-decoration process (PDP) using PCBM in chlorobenzene anti-solvent, was utilized in fully printable perovskite solar cells with carbon electrode forming relaying delivery of excited state electrons. The champion device with PCBM achieved a power conversion efficiency of 14.12%. • Forming gradient PCBM/Perovskite heterojunction with post-decoration process. • Relaying delivery of excited state electrons. • Improving the photovoltaic performance parameters significantly. The high-temperature fabrication process for fully printable perovskite solar cell (PSC) limits its synchronization passivation with device fabrication. Herein we have creatively developed a post-decoration process (PDP) using phenyl-C 61 -butyric acid methyl ester (PCBM) in chlorobenzene anti-solvent, which not only induces the regrowth of perovskite crystals reducing grain boundaries, but also realizes the relaying delivery of excited state electrons from perovskite to TiO 2 in virtue of the ultra-thin PCBM/perovskite heterojunction. The champion device with PCBM achieved a power conversion efficiency of 14.12% with an open circuit voltage of 0.91 V, a current density of 24.03 mA/cm2 and a fill factor of 0.64. It provides a simple approach towards high efficiency without sacrificing long-term stability of fully printable perovskite solar cells. [ABSTRACT FROM AUTHOR]

We investigated the changes in the organic transistor characteristics of poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) thin films upon high-energy gamma-ray irradiation. Devices based on both organic semiconductors showed a lower field-effect mobility and electrical current levels after gamma-ray irradiation. The threshold voltage of P3HT transistors shifted negative, while that of PCBM-based devices shifted positive. These changes in electrical performance of the devices can be utilized as a gamma-ray sensing elements. [ABSTRACT FROM AUTHOR]

• Copper Oxide nanoparticles were inserted in a bulk-heterojunction solar cell. • Power conversion efficiency increased 35% for an optimum nanoparticle concentration. • Origin of the optimum is a competition between charge mobility and trap density increase. Organic and metal oxide-based hybrid solar cells have drawn attention for their improved device performance along with mechanical stability and cost-effectiveness. We investigated the incorporation of various concentrations of copper oxide (CuO) nanoparticles (NPs) blended with poly 3-hexylthiophene: [ 6 , 6 ]-phenyl-C 61 -butyric methyl ester (P3HT:PCBM) bulk-heterojunction devices. With an optimum concentration of CuO NPs in P3HT: PCBM the devices power conversion efficiency is about 35% larger than without CuO NPs. The overall improvement in the photovoltaic properties of the device is attributed to the improved optical absorption, crystallinity and roughness of the photoactive layer confirmed by the AFM and XRD characteristics of the blended films. Beyond optimum nanoparticle concentration deteriorates the device performance from high trapped charge density as evidenced by steady-state current-voltage characteristics and charge-extraction-by-linearly-increasing-voltage (CELIV). [ABSTRACT FROM AUTHOR]

In this work, we focus on designing a donor copolymer for the improvement of photovoltaic performance. Using density functional theory and time-dependent density functional theory, we investigated the electronic, optical and charge transfer properties of a series of new designed copolymers based on the reported copolymer Pa 0 which is composed of a donor fluorene unit and an acceptor 4,7-dithien-2-yl-2,1,3-benzothiadiazole. We first obtained two copolymers Pb 0 and Pc 0 by replacing the benzothiadiazole (BTZ) with two different strong acceptors units to decrease the LUMO level of conjugated polymers. Then, we designed Pa 1 , Pb 1 and Pc 1 copolymers by adding a substituent methyl group to the thiophene spacer unit (T). Bulk-heterojunction photovoltaic cells were designed with the copolymers as the donors and PCBM as the acceptor. Our results show that the cells based on Pb 1 and Pc 1 have a suitable electronic structure with energy conversion efficiency exceeding 10%. Moreover, we used Marcus theory to evaluate the intermolecular charge transfer (inter-CT) and recombination (inter-CR) rates of these cells (copolymer/PCBM). The ratio K inter-CT /K inter-CR of Pc 1 /PCBM heterojunction is about 106 times higher than that of Pb 1 /PCBM which clearly reveals that the designed donor molecule Pc 1 will be a promising candidate for high performance organic photovoltaic devices. Our strategy to design novel donor copolymers provides a theoretical guideline for further improving in electrical, optical properties and the efficiency of the photovoltaic device. Image 1 • DFT and TD-DFT theoretical methods. • Narrow band gap polymers. • Intermolecular charge transfer and recombination rates. • Calculated results give a direction to design novel donor polymer for high-performance organic photovoltaic device. [ABSTRACT FROM AUTHOR]

Abstract We report a method to produce nanosecond pulsed laser induced periodic surface structures (LIPSS) on spin-coated [6,6]‑phenyl C71-butyric acid methyl ester (PC 71 BM) films exhibiting a photoinduced resist-free imprinting (PRI) property. LIPSS in PC 71 BM are resist free and can be solvent developed, under certain conditions, leaving the laser illuminated zone as an undissolved residue. LIPSS prepared with a wavelength of 532 nm selectively preserve the electrical conductivity on the LIPSS valleys. The heterogeneous conducting pattern consisting in conducting valleys and less conducting hills observed in the LIPSS has been interpreted as due to a reduction in the crystallinity of the hills provoked by the fast heating/cooling process induced by every laser pulse. On the basis of the experiments we propose that irradiated PC 71 BM films: i) suffer a fast heating/cooling process tending to reduce the overall crystallinity of the LIPSS and therefore decreasing the electrical conductivity of the hills while leaving a remnant conducting film underneath the hills, ii) during laser irradiation the sample suffers a heat treatment leading to the development of a buried phase with enhanced crystallinity, close to the silicon substrate, formed by larger crystals with enhanced electrical conductivity and iii) further solvent treatment reveals the buried phase which remains in the form of partially electrically conducting nanowires. These results point towards the potential use of the described technology for nanofabrication of organic electronic devices. Graphical abstract Unlabelled Image Highlights • Laser induced periodic surface structures are formed on fullerene derivative films. • LIPSS are resist free and can be solvent developed leaving an undissolved residue. • The electrical conductivity is selectively preserved on the LIPSS valleys. • Laser irradiation heats and cools the sample decreasing crystallinity. • Larger crystals with enhanced electrical conductivity are formed in a buried phase. [ABSTRACT FROM AUTHOR]

Eight novel organic compounds with donor-π-acceptor (D-π-A) structure were designed for use as donors in organic bulk heterojunction (BHJ) solar cells. The molecules have thieno[2,3-b]indole as donor, methylene malononitrile as electron acceptor group, and a π-spacer bridge based on thiophene and benzene or its derivatives. The designed compounds were studied using density functional theory (DFT) and time-dependent DFT approaches, to shed light on how the π-conjugation order influences the performance of corresponding photovoltaic solar cells. The study includes prediction of the energy of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels, the energy gap, Voc (the open-circuit voltage), the λmax of absorption, and other quantum-chemical parameters. The results show that, the greater the number of thiophenes present in the bridge, the better the compound as a donor for BHJ solar cells. The theoretical power conversion efficiency calculated for the designed products reaches 6%. [ABSTRACT FROM AUTHOR]

Abstract Aqueous colloids of conjugated polymers (CP), such as poly(3-hexylthiophene) (P3HT), are an attractive alternative for processing CP-based materials because (1) the microstructure of the conjugated polymers can be optimized during the formation of the colloid and (2) this method can significantly reduce the amount of hazardous organic solvents used during manufacturing. This investigation addresses the optimization of the polymer structure by studying the intrachain order of P3HT aggregates pre-assembled in mixtures of chloroform (CF) with dichloromethane (DCM) and subsequently dispersed in aqueous solutions of the surfactant sodium dodecyl sulfate (SDS) using a mini-emulsion method. Compared to an amorphous solution of P3HT, the observed intrachain order of P3HT in the colloids is much higher when using aggregate dispersions pre-assembled in the CF:DCM mixtures. Similar results are observed for aggregate dispersions of a benchmark organic photovoltaic system composed of P3HT and the fullerene derivative phenyl-C 61 -butyric acid methyl ester (PCBM), but in this case the intrachain order of P3HT in the P3HT:PCBM colloids is anomalously higher than the pure P3HT colloids. Atomic force microscopy (AFM) imaging reveals changes in the dominant structural motifs and morphology of the colloidal P3HT films, but not in a way that correlates with films processed from the aggregate dispersions. Graphical abstract Unlabelled Image Highlights • Aggregate dispersions of P3HT improve the intrachain order in aqueous, SDS-stabilized P3HT colloids. • The assembly of P3HT in the aqueous colloids is primarily dictated by the organic solvent mixture. • The intrachain order in P3HT:PCBM colloids are markedly higher than colloids of pure P3HT. • Variations in the dominant structural motifs are observed in the colloidal P3HT films. [ABSTRACT FROM AUTHOR]

In this work, the power conversion efficiency (PCE) of bulk heterojunction organic solar cell is improved by adding PEG (polyethylene glycol) in the solution of P3HT and PCBM blend. The short circuit current and fill factor are increased by adding PEG with the molecular weight of 300, whereas the open circuit voltage is not changed. On the other hand, PCE becomes worse by adding PEG with the molecular weight of 6000. It was observed by field-emission scanning electron microscopy that the additional layer was formed under the active layer during spin coating by phase separation. The stability of solar cell is also improved with introducing the PEG layer. These results were explained by the formation of the PEG interfacial layer under the P3HT:PCBM active layer, which acts as a hole transport layer and also blocks the water diffusion from PEDOT:PSS toward the metal electrode. [ABSTRACT FROM AUTHOR]

Abstract The influence of blending ratio on resistive switching effect in donor-acceptor type composite of [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) and poly(N -vinylcarbazole) (PVK)-based memory devices are investigated. Current-voltage (I - V) curves for the ITO/PCBM + PVK/Al devices with 9 wt.% of PCBM showed a current bistability with a maximum OFF/ON resistance ratio of 9 × 104, which was 100 times larger than that of the device with 23 wt.% of PCBM and was 2000 times larger than that of the device with 41 wt.% of PCBM. Furthermore, the threshold voltage obviously decreased as the PCBM concentration increases. The retention time was above 105 s indicative of the memory stability of the as-fabricated devices. The I - V characteristics at OFF state dominantly comply with the rules of space-charge-limited-current behaviors, and I - V curve at ON state obey Ohmic laws. The proposed device suggests a promising approach for adjustale OFF/ON resistance ratio and threshold voltage in electronic memory devices. Graphical abstract Image Highlights • The influence of blending ratio on resistive switching effect are investigated. • The threshold voltage obviously decreased as the PCBM concentration increases. • The resistance ratio obviously increased with the PCBM concentration decreases. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study is to investigate the stability of the active layer of polymer solar cells from the effect of UV-visible light irradiation using different conditions with respect to time. The active layers were composed of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM), deposited on conductive glass substrates through spin coating. These samples are placed in a UV-visible light exposure chamber using different conditions (heat and water) over the specific periods of time. The samples are analyzed by UV-visible absorption spectroscopy, X-ray photoelectron spectroscopy and Fourier transforms infrared spectroscopy (FTIR) measurements. The results indicate that after continuous exposure to UV irradiation for 72 and 120 h, the sample shows a significant decrease in absorption of the main peak. The sample shows around 25% loss in absorption (main peak) after 72 h of irradiation. The FTIR results illustrate a progressive decrease in intensities of all typical absorption peaks owing to P3HT ring scission, side chain oxidation as well as degradation of the side groups of PCBM.Graphical abstract: [ABSTRACT FROM AUTHOR]

Fast scanning chip calorimetry was used to perform an elaborate isothermal study of poly(3‐hexyl thiophene)/[6,6]‐phenyl‐C61‐butyric acid methyl ester (P3HT/PC61BM) submicron layers. The used scanning rates of 30 000 K s−1 allow for a 'true' isothermal study, where non‐isothermal effects are avoided. Results were obtained over a wide temperature range for the 1:1 composition, used in organic solar cells, and for selected temperatures for the 3:7 composition. The results can be clearly interpreted according to the eutectic behaviour expected for this system, with the 1:1 composition being enriched in P3HT and the 3:7 composition being enriched in PC61BM. In both cases, the start of the melting trajectory corresponding to the eutectic transition coincided with the Tg of PC61BM. This is in agreement with earlier studies that report a vitrification effect caused by PC61BM. A bell‐shaped curve of isothermal crystallization rates could be constructed for the 1:1 composition, where the Tg of the mixed amorphous phase as well as of the separate components can be seen to play a role. For the 3:7 composition, clear indications are observed that a vitrified PC61BM phase can be formed in which isothermal crystallization takes place. © 2018 Society of Chemical Industry An isothermal study of poly(3‐hexyl thiophene)/[6,6]‐phenyl‐C61‐butyric acid methyl ester (P3HT/PC61BM) submicron layers was performed by chip calorimetry. The results obtained correspond to eutectic behaviour, and may provide a rationale for optimizing organic photovoltaic active layers by annealing. [ABSTRACT FROM AUTHOR]

Effects of a newly synthesized additive, 2,2'5,5'-tetrathiophene-3,3'-hexyldithiophene (TTH), on the performance of polymer solar cells (PSCs) based on poly(3-hexylthiophene):[6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) bulk-heterojuction were investigated. The PSC with a non-annealed P3HT:PCBM:TTH blend film showd an increase in the short-circuit current and the fill factor, resulting in a significant enhancement in the power conversion efficiency, compared to that of a reference cell without the TTH additive. It was revealed that the addition of 5wt% TTH to the P3HT:PCBM blend film facilitated the crystallization (ordering) of P3HT chains without even post-thermal annealing, leading to a higher absorbance and a larger crystal size of P3HT, and thereby increasing the short-circuit current and the fill factor. [ABSTRACT FROM AUTHOR]

Abstract We introduced phenyl-C61-butyric acid methyl ester (PCBM) as an electron transport layer to improve the performance of metal-oxide-free perovskite solar cells (PSCs) using high-conductivity poly(3,4-ethylenedioxylenethiophene):poly(styrene sulfonate) (PEDOT:PSS) as the cathode. The work function of the PEDOT:PSS was tuned from −5.08 to −4.05 eV by using polyethylenimine, improving the electron collection. Using PCBM improved the electron transport and suppressed the charge recombination of the PSCs. The power-conversion efficiency (PCE) of the rigid PSCs (on glass substrates) was significantly improved from 12.5% to 13.9%, and the open-circuit voltage, short-circuit current density, and fill factor were improved simultaneously. The long-term stability of the PSCs was also improved: the PCE degradation of the PSCs without encapsulation decreased from 18.4% to 13.0% after 114 h. Using a 37-nm PCBM layer, the flexible PSCs on polyethylene naphthalate substrates exhibited a high PCE of 11.4% with good bendability. Our results indicate that using PCBM as an electron transport layer in metal-oxide-free PSCs is a feasible method for the large-scale roll-to-roll production of PSCs. Graphical abstract Image 1 Highlights • High-performance metal-oxide-free PSC produced with PCBM as electron transport layer. • High PCE of 13.9% was achieved for rigid PSCs on a glass substrate. • Long term stability of the PSCs was also improved upon using PCBM. • Flexible PSCs on a PEN substrate exhibited a high PCE of 11.4% with good bendability. [ABSTRACT FROM AUTHOR]

Abstract The self-assembled bilayer lipid membrane (BLM) is a basic component in cell membranes. BLMs have gigaohm-level electrical resistivities and work as barrier walls for cells. In this study, the electrical conductivities across free-standing, phenyl‑C 61 ‑butyricacid‑methyl ester (PC 60 BM)-doped BLMs in a buffer solution are investigated to confirm their applicability for electronic biodevices. An apparent increase in the current across the BLM due to exposure to Xe-lamp light with wavelengths ranging from 888 to 300 nm is observed, compared to non-doped BLMs. It is possible that the doped PCBM works as a carrier mediator for electrons and/or ions in the buffer solution. The possibility of making artificial electronic valves using the BLM is discussed in this paper. Highlights • The electrical conductivities across PC 60 BM doped BLMs in a buffer solution are investigated. • A current increase across the BLM with an exposure to Xe-lamp light is observed. • The doped PCBM might work as an electrical carrier mediator. [ABSTRACT FROM AUTHOR]

Abstract Organic-inorganic hybrid perovskites have attracted great attentions for photovoltaic applications due to impressive energy conversion efficiency and low cost fabrication. This article reports the effect of photogenerated dipoles in the electron transport layer (ETL) on the photovoltaic actions in perovskite solar cells (PSCs). A nonfullerene material ITIC with optically induced dipoles was doped into PCBM acting as ETL in inverted planar structure PSCs (ITO/PEDOT:PSS/MAPbI 3-x Cl x /ETL/PEI/Ag). The power conversion efficiency (PCE) of PSCs increases from 13.48% to 14.52% with introducing ITIC into ETL. The capacitance measurements indicate that optically induced dipoles can decrease interfacial charge accumulation. Furthermore, impedance spectroscopy suggests the charge recombination as well as ionic migration are reduced with ITIC doped ETL. Steady and transient PL spectra reveal that the electron extraction is more efficient with optically induced dipoles in the ETL. These results provide unique design of ETL in perovskite solar cells. Graphical abstract Image Highlights • ITIC with optically polarizable molecules was introduced into ETL to enhance the photovoltaic performance of PSCs. • The effect of photogenerated dipoles on photovoltaic actions in PSCs were revealed by impedance spectroscopy and PL spectra. • Our results provide a unique method for improving photovoltaic actions in inverted planar structure PSCs. [ABSTRACT FROM AUTHOR]

We demonstrate that a GaN nanowire array can be used for efficient charge transfer between the organic photovoltaic layer and silicon in a Si/GaN/P3HT:PC71BM inverted hybrid heterostructure. The band alignment of such a material combination is favorable to facilitate exciton dissociation, carrier separation and electron transport into Si. The ordered nature of the GaN array helps to mitigate the intrinsic performance limitations of the organic active layer. The dependence of photovoltaic performance enhancement on the morphology of the nanostructure with nanowire diameters 30, 50, 60, 100 and 150 nm was studied in detail. The short circuit current was enhanced by a factor of 4.25, while an open circuit voltage increase by 0.32 volts was achieved compared to similar planar layers.

Two boron dipyrromethene (BODIPY) triads, namely BODIPY-1 and BODIPY-2, were synthesized and incorporated with poly-3-hexyl thiophene: (6,6)-phenyl-C61-butyric acid methyl ester (PCBM) P3HT:PCBM. The photovoltaic performance of BODIPY:P3HT:PCBM ternary solar cells was increased, as compared to the control binary solar cells (P3HT:PCBM). The optimized power conversion efficiency (PCE) of BODIPY-1:P3HT:PCBM was improved from 2.22% to 3.43%. The enhancement of PCE was attributed to cascade charge transfer, an improved external quantum efficiency (EQE) with increased short circuit current (Jsc), and more homogeneous morphology in the ternary blend.

Gold nanoparticles (AuNPs) deposited at the interface of the intermediate layer [poly (3,4ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)] and poly(3-hexylthiophene):[6,6]-phenylC61-butyricacidmethylester (P3HT:PCBM) active layer were found to significantly increase organic solar cell performance. Organic solar cell devices with different solvents, such as the chlorobenzene (CB), dichlorobenzene (DCB), chloroform (CF), and co-solvent Chlorobenzene: Dichlorobenzene (CB:DCB), Chlorobenzene:Chloroform (CB:CF), and Dichlorobenzene:Chloroform (DCB:CF) were fabricated. The photo-physical properties of these devices with different solvents are investigated. It can be found that, absorption spectrum of the blend becomes broad with different solvents, which is highly desirable for an organic solar cell devices. Film morphology is evaluated by Atomic Force Microscopy (AFM). XRD patterns and External Quantum Efficiency (EQE) measurements are also performed for the devices. The efficiency enhancement for the device with (CB:CF) is more significant than for other solvents. With different solvents, the solar cells upon (CB:CF) give Power Conversion Efficiency (PCE) of 3.6%, in contrast to 3.2% for (CB), 2.06% for (DCB), 3% for (CF), 2.55% for (CB:DCB), and 2.9% (DCB:CF) devices.

Abstract We investigate the charge carrier dynamics of inverted organic solar cells (OSCs) based on PffBT4T-2OD: PCBM and PTB7: PCBM – the two leading systems among the OSCs based on polymer-fullerene bulk-heterojunction – to elucidate the origin of their performance difference. Transient absorption spectroscopy (TAS) and photo-electrochemical impedance spectroscopy (photo-EIS) were employed to unravel the photo-physics that govern the cell operation of these two highly efficient bulk heterojunction OSCs. While photo-EIS indicates that the two systems under study exhibit similar behavior in terms of recombination, TAS results reveal that PffBT4T-2OD: PCBM systems not only have higher charge generation rate but also more efficient charge transfer than PTB7: PCBM systems, leading to the power conversion efficiency of PffBT4T-2OD: PCBM-based OSCs (9.16%) that is higher than that of PTB7: PCBM-based OSCs (6.44%). Graphical abstract Image 1 Highlights • Charge carrier dynamics of PffBT4T-2OD: PCBM and PTB7: PCBM OSCs have been compared. • TAS and Photo-EIS measurements along with optical simulation were carried out. • Higher PCE for PffBT4T-2OD: PCBM OSCs is due to better absorption and carrier collection efficiency. [ABSTRACT FROM AUTHOR]

Abstract By introducing [6,6]-phenyl-C 61 -butyric acid methyl ester as an effective additive in the perovskite precursor solution, we demonstrate a grain interface-engineering approach for universally increasing the efficiency of perovskite solar cells based on the printable triple mesoscopic structure of TiO 2 /ZrO 2 /carbon. These perovskite solar cells have advantages of low-cost and are easy to scale up, however the micrometer-thick mesoscopic layers and one-step dropping method challenge perovskite crystallization in such devices, resulting in non-ignorable charge-recombination loss. With adding an optimized 0.25 mg mL−1 PCBM into the perovskite precursor solution, we improve the champion PCE of PSCs using MAPbI 3 perovskites from 8.58% to 12.36% and that of PSCs using MAPbI 2.95 (BF 4) 0.05 perovskites from 12.77% to 14.26%. We find that the PCBM additive affects the perovskite morphology, facilitates the photo-generated charge separation and suppresses the charge recombination in the device, thus yielding a universal improvement of MPSC performance. This work gives a new insight towards designing high performance perovskite solar cells. Graphical abstract Image 1 Highlights • PCBM additive is employed in printable hole-conductor-free perovskite solar cells. • PCBM additive facilitates the photo-generated charge separation and suppresses the charge recombination in the device. • PCBM additive demonstrates universal positive effect on different perovskite precursor. • Enhanced performance and reproducibility is obtained. [ABSTRACT FROM AUTHOR]

Highlights • ITIC was a promising additive for PC 61 BM ETL in planar inverted PSCs. • ITIC featured the proper LUMO level and decent electrical conductivity. • The PCE and J sc were 13.3% and 13.5% enhancements compared with the undoped device. Abstract A small molecule 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 ′]-dithiophene (ITIC) was used as the additive for the electron transport layer (ETL) of phenyl-C61-butyric acid methyl ester (PC 61 BM) in planar inverted perovskite solar cells (PSCs) fabricated by the flash method. Due to the proper LUMO level and decent electrical conductivity of ITIC, the photovoltaic properties of planar inverted PSCs based on the smooth PC 61 BM:ITIC (2 wt%) ETL were promoted, and the power conversion efficiency (PCE) and the short-circuit current density (J sc) of the devices were increased to 12.41% and 18.53 mA cm−2, respectively, which were 13.3% and 13.5% enhancements relative to those of the undoped control devices. Therefore, ITIC was a promising additive for PC 61 BM ETL in inverted PSCs and the photovoltaic properties of devices could be improved accordingly. [ABSTRACT FROM AUTHOR]

Fullerene‐based materials are widely used as electron acceptors in organic bulk‐heterojunction solar cells; yet, they have rarely been used as the only photoactive component due to their low absorbance and limited charge generation efficiency. However, blending the wide‐bandgap p‐type material copper (I) thiocyanate (CuSCN) with [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC70BM) leads to the formation of a unique mesostructured p‐n like heterointerface between CuSCN and PC70BM and solar cells with a power conversion efficiency (PCE) of up to 5.4%. Here, we examine in detail the reasons for the surprisingly good device performance and elucidate the charge photogeneration and recombination mechanisms in CuSCN‐based devices with PC70BM as the exclusive light‐absorbing material. Our studies clearly demonstrate that a substantial fraction of the photocurrent in the CuSCN‐based devices results from improved dissociation of fullerene excitons and efficient charge transfer at the CuSCN:PC70BM interface combined with reduced geminate and nongeminate charge recombination losses. Our results have implications beyond the fullerene‐based devices studied here, as they demonstrate that careful selection of a mesostructured p‐type transparent semiconductor paves the path to a new type of efficient single photoactive material solar cells. [ABSTRACT FROM AUTHOR]

The perovskite solar cells have attracted great attention owing to their low cost and high performance. For perovskite solar cells, metal oxides demonstrated great potential with much higher charge carrier mobility and superior stability than organic materials. In this study, we employed NiO as hole transport layer and chloride-doped CH 3 NH 3 PbI 3 (CH 3 NH 3 PbI 3−x Cl x ) as absorber due to its enhanced performance. We investigated the effects of several parameters on the solar cell performance through device simulation. It was found that solar cell performance was related to the doping concentrations of NiO and PCBM, and the thicknesses of perovskite and NiO interlayer. The optimized performance of perovskite solar cells with power conversion efficiency (PCE) of 22.0% was achieved when doping concentrations of NiO and PCBM were 1 × 10 17  cm −3 and 1 × 10 19  cm −3 , respectively, and thicknesses of perovskite and NiO were 450 nm and 30 nm, respectively. Moreover, a high PCE of 18.0% was obtained based on experimental condition. These results showed that this kind of solar cell was a potential choice for perovskite solar cells with high efficiency. [ABSTRACT FROM AUTHOR]

ABSTRACT: It is known that poly(3‐alkylthiophene) (P3AT) side‐chain length notably influences the photovoltaic performances of relating devices. However, comprehensively study on its impact on the structures of P3ATs and their blends with [6, 6]‐phenyl‐C61 butyric acid methyl ester (PCBM) is insufficient. By using solid‐state NMR and FTIR techniques, four P3ATs and their PCBM blends are investigated in this work, focusing on the phase structures as modulated by side‐chain length. Recently, we revealed multiple crystalline main‐chain packings of packing a and b together with a mesophase in poly(3‐butylthiophene) (P3BT) films (DOI: 10.1021/acs.macromol.6b01828). Here, the semicrystalline structures are investigated on poly(3‐hexylthiophene) (P3HT), poly(3‐octylthiophene) (P3OT), and poly(3‐dodecylthiophene) (P3DDT) with traditional form I modification, where packing a and the amorphous phase are probed. Furthermore, crystallized side chain within packing a is detected in both P3OT and P3DDT films, which shows a FTIR absorption at 806 cm−1. Structural studies are also conducted on P3AT:PCBM blends. Compared with the pure P3ATs, the polymer crystallinities of the blends show reduction of about 40% for P3OT and P3DDT, whereas only about 10% for P3HT. Moreover, in P3BT:PCBM and P3HT:PCBM, the crystalline polymers and PCBM are phase separated, while in P3OT:PCBM and P3DDT:PCBM, blend components are mostly miscible. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 751–761 [ABSTRACT FROM AUTHOR]

Abstract: Fullerenes and their derivatives are widely used as electron acceptors in bulk‐heterojunction organic solar cells as they combine high electron mobility with good solubility and miscibility with relevant semiconducting polymers. However, studies on the use of fullerenes as the sole photogeneration and charge‐carrier material are scarce. Here, a new type of solution‐processed small‐molecule solar cell based on the two most commonly used methanofullerenes, namely [6,6]‐phenyl‐C61‐butyric acid methyl ester (PC60BM) and [6,6]‐phenyl‐C71‐butyric acid methyl ester (PC70BM), as the light absorbing materials, is reported. First, it is shown that both fullerene derivatives exhibit excellent ambipolar charge transport with balanced hole and electron mobilities. When the two derivatives are spin‐coated over the wide bandgap p‐type semiconductor copper (I) thiocyanate (CuSCN), cells with power conversion efficiency (PCE) of ≈1%, are obtained. Blending the CuSCN with PC70BM is shown to increase the performance further yielding cells with an open‐circuit voltage of ≈0.93 V and a PCE of 5.4%. Microstructural analysis reveals that the key to this success is the spontaneous formation of a unique mesostructured p–n‐like heterointerface between CuSCN and PC70BM. The findings pave the way to an exciting new class of single photoactive material based solar cells. [ABSTRACT FROM AUTHOR]

Abstract: In the last few years, all‐inorganic perovskite CsPbBr3 nanocrystals (NCs) have attracted tremendous attention for its high carrier mobility, long carrier diffusion length, excellent visible light absorption, and more importantly superior air stability. In fact, photodetectors (PDs) are designed and fabricated using the CsPbBr3 NCs with very high performance. Herein, by optimizing the NC shape, size, and surface passivation, the CsPbBr3 PDs are developed with an even higher performance. It is found that the PDs based on CsPbBr3 nanoribbons show the best photoresponse among all common NC structures synthesized. Moreover, it is found that 6,6‐phenyl‐C61‐butyric acid ethyl ester can be used to passivate defects on the CsPbBr3 nanoribbon surface and shows the charge transfer. As a result, the device displays superior photoresponsivity (R = 18.4 A W−1), excellent signal‐to‐noise ratio, as high as 104, and a very sharp rise/decay time (8.7/3.5 ms). The method demonstrated may offer an attractive strategy to improve sensitivity for all‐inorganic perovskite PDs in general. [ABSTRACT FROM AUTHOR]

The impact of PCBM and PCBM on the thermal stability of two low-bandgap conjugated polymers widely used in organic photovoltaic applications, namely PTB7 and PTB7-Th (also known as PBDTTT-EFT), was studied under nitrogen and air atmospheres. The thermal stability effect observed is mainly additive, i.e., the stability of the composites is similar to the weighted average of the stabilities of the individual components. The thiophene-substituted polymer (PTB7-Th) displays higher thermal stability, both in nitrogen and air, than its ether-substituted analogue (PTB7). The corresponding bulk heterojunction composites display the same order of relative thermal stabilities, i.e., PTB7-Th:PC71BM (1:1.5) > PTB7:PC71BM (1:1.5), which interestingly is also the order of lifetime stabilities reported in the literature for the corresponding OPV devices. These results suggest that simple and rapid thermogravimetry tests might be used as a valid rapid screening test to infer on the relative lifetime stability of OPV devices. [ABSTRACT FROM AUTHOR]

In this paper, high efficient and stable planar perovskite solar cells (PKSCs) have been designed and fabricated via employing high transparent Mg-doped ZnO films with excellent electron transport ability as a novel class of electron transport layers (ETLs). Due to the optimized band alignment by Mg doping, the photogenerated electron injection and charge extraction from the perovskite film to ETL have been facilitated effectively and the planar PKSC based on 2% Mg-doped ZnO and MAPbI 3 yields the maximum power conversion efficiency (PCE) of up to 16.74%. Meanwhile, a higher PCE of 17.85% through a phenyl C 60 butyric acid methyl ester (PCBM) interfacial layer between the 2% Mg-doped ZnO and perovksite layer has been achieved for the first time. Moreover, the PKSCs with 2% Mg-doped ZnO/PCBM composite ETLs also demonstrate outstanding long term device stability and up to 91% of original PCE of the PKSCs, which can be retained even after exposure in ambient conditions over three-months. [ABSTRACT FROM AUTHOR]

Tinted and colour-neutral semitransparent organic photovoltaic elements are of interest for building-integrated applications in windows, on glass roofs or on facades. We demonstrate a semitransparent organic photovoltaic cell with a dry-laminated top electrode that achieves a uniform average visible transmittance of 51% and a power conversion efficiency of 3%. The photo-active material is based on a majority blend composed of a visibly absorbing donor polymer and a fullerene acceptor, to which a selective near-infrared absorbing cyanine dye is added as a minority component. Our results show that organic ternary blends are attractive for the fabrication of semitransparent solar cells in general, because a guest component with a complementary absorption can compensate for the inevitably reduced current generation capability of a high-performing binary blend when applied as a thin, semitransparent film. [ABSTRACT FROM AUTHOR]