PCE Value Research Articles

From binary to quaternary: high-tolerance of multi-acceptors enables development of efficient polymer solar cells

Two typical fullerene derivatives were incorporated into a PTB7-Th:IEICO-4F binary host to enable development of efficient quaternary polymer solar cells with PCE values up to 12.52%.

Syntheses and Characterization of Benzotriazole, Thienopyrroledione, and Benzodithiophene Containing Conjugated Random Terpolymers for Organic Solar Cells

Two random terpolymers bearing alkoxy-benzodithiophene as an electron-rich unit and N-octylthieno[3,4,c]pyrrole-4,6-dione (TPD) as an electron deficient group with thiophene and selenophene π bridges, were synthesized and characterized. Electrochemical, optical properties of the polymers were analyzed to get an insight on the effect of different π bridges. Photovoltaic performances of the polymers were investigated with a conventional device architecture. PBTS, PBTSe based polymer solar cells (PSCs) exhibited power conversion efficiency of 3.32% and 3.19%. PCE of PBTS:PC71BM based PSCs were improved to 4.30% with the addition of 1% (vol/vol) 1,8-diiodooctane (DIO) as a solution processing additive. With the introduction of diphenyl ether (DPE) as the solvent additive, PBTSe based polymer solar cells attained 5.15% PCE value due to the formation of the interpenetrated network structure of domains.

Thermal impact on (001) faceted anatase TiO2 microtablets and nanowalls's lattices and its effect on the photon to current conversion efficiency

Thermal annealing impact on the properties of (001) faceted anatase TiO2 with two different morphologies, i.e. microtablet (TMT) and nanowall (TNW), have been examined by observing the change in their lattice paramaters and photovoltaic properties when being subjected to several thermal annealing intervals, i.e. from 1 to 7 h, at 450 °C, under ambient atmosphere. The TMT and TNW were prepared on ITO substrate via liquid phase deposition method. The TMT is characterized by a squared tablet-like shape meanwhile the TNW is a squared-platelet morphology nanostructures. The XRD and Raman analysis indicated that both TMT and TNW underwent a lattice expansion with the increasing of the annealing interval. For example, the Raman results indicates that the main Raman character of Eg, i.e. OTiO bridge bending oscilation, as well as B1g and A1g, i.e. TiO strain oscilation, blue-shifted with the increasing of the thermal annealing duration. However, the expansion is approximately 1.4% higher in TNW compared to TMT. Regarding the surface chemistry activity, it is higher on the TNW and it increases with the increasing of thermal annealing impact. Meanwhile, the TMT showed a tendency to steadily decrease in its surface chemistry activity with the increasing of the thermal annealing impact. The modification in the lattice parameters and the surface chemistry activity have effectively modified the TMT and TNW's photovoltaic performance. In typical process, the power conversion efficiency improve from 1.8% to 3.2% for DSSCs utilizing TMT and 1.5%–3.0% in TNW when the thermal annealing impact was increased. In general, the TNW exhibits relatively higher electrical and optical properties stability compared to TMT that is indicated by a small variation in the PCE value when the thermal impact further increased up to almost double above the optimum condition.

Elucidating the impact of N-arylanilino substituents of squaraines on their photovoltaic performances

Abstract Squaraines have attracted increasing research attention for organic photovoltaic applications because of their facile and low-cost synthesis, and intense and broad absorption in the visible and near-infrared (Vis-NIR) regions. Herein, three new squaraines, N-phenylanilino substituted SQ-EP, N-2-naphthylanilino substituted SQ-EN, and N-fluorenylanilino substituted SQ-EF, were developed for improving the hole mobility of aniline-based squaraines. The substitution effect of N-arylanilino groups on the optoelectronic properties of squaraines was investigated. These squaraines exhibited similar absorbance spectra, HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energy levels, and hole mobilities in their neat films. However, compared to their neat films, the hole mobility of the SQ-EP-based BHJ blend film showed the smallest decrease when blending with PC71BM ([6,6]-phenyl C71 butyric acid methyl ester). Besides, morphological studies have shown that a phase separation of 20–30 nm can only be observed in the SQ-EP/PC71BM blend film. Consequently, a solution-processed bulk-heterojunction (BHJ) organic photovoltaic (OPV) device fabricated with the as-cast SQ-EP/PC71BM blend film exhibited obviously higher power conversion efficiency (PCE: 5.4%) than those of the SQ-EN/PC71BM (PCE: 4.3%) or SQ-EF/PC71BM systems (PCE: 2.8%). This is one of the highest recorded PCE values in aniline-based squaraines single-junction BHJ-OPV devices. This much-enhanced PCE can be attributed to the significant increases in short-circuit current density (Jsc) and fill factor (FF) of the SQ-EP/PC71BM-based OPV device.

Effects of Alkoxy and Fluorine Atom Substitution of Donor Molecules on the Morphology and Photovoltaic Performance of All Small Molecule Organic Solar Cells.

Two benzothiadiazole (BT)-based small-molecule donors, SM-BT-2OR with alkoxy side chain and SM-BT-2F with fluorine atom substitution, were designed and synthesized for investigating the effect of the substituents on the photovoltaic performance of the donor molecules in all small molecule organic solar cells (SM-OSCs). Compared to SM-BT-2OR, the film of SM-BT-2F exhibited red-shifted absorption and deeper HOMO level of −5.36 eV. When blending with n-type organic semiconductor (n-OS) acceptor IDIC, the as-cast devices displayed similar PCE values of 2.33 and 2.76% for the SM-BT-2OR and SM-BT-2F-based devices, respectively. The SM-BT-2OR-based devices with thermal annealing (TA) at 120°C for 10 min showed optimized PCE of 7.20%, however, the SM-BT-2F-based device displayed lower PCE after the TA treatment, which should be ascribed to the undesirable morphology and molecular orientation. Our results reveal that for the SM-OSCs, the substituent groups of small molecule donors have great impact on the film morphology, as well as the photovoltaic performance.

Transparency, moisture barrier property, and performance of the alternative solar cell encapsulants based on PU/PVDC blend reinforced with different types of cellulose nanocrystals

Two different types of cellulose nanocrystals, derived from water hyacinth fibers and microfibrillated cellulose (MFC), were prepared using an acid hydrolysis treatment. These cellulose nanocrystals (CNCs) were further used as barrier enhancing fillers for polyurethane (PU) blended with 25 wt% of poly(vinylidene dichloride) (PVDC). The aim of this study was to investigate the effects of types and concentration of CNCs on mechanical, optical and barrier properties of polymer composite films. The feasibility of applying the obtained composite films as an encapsulating material for enhancing the lifetime of dye sensitized solar cells (DSSC) was also of interest. The acid hydrolysis of the MFC-yielded rod-shaped cellulose nanocrystals (CNCm) while the acid-hydrolyzed water hyacinth led to a formation of spherical-shaped cellulose nanocrystals (CNCw). Regardless of the types of CNCs, the optical transparency of the composite films was maintained well above 60%. According to results in this study, the most efficient film with the lowest water vapor transmission rate of 0.0517 g m−2 day−1 was the PU/PVDC film reinforced with 0.1 wt% of CNCm. The encapsulants made from this composite could prolong the lifetime of the DSSC devices for up to 14 days, with the normalized PCE value of 0.78. Overall, this work showed that the considerations of the barrier properties of the polymer encapsulants alone are insufficient to ensure that the system would be effective. An interfacial adhesion between the encapsulants and the electrodes, as well as some side reactions between polymers and chemicals inside the fabricated cell, should also be taken into account.

Integration of Multiwalled Carbon Nanotubes in Bulk Heterojunction CdSe/PCPDTBT Hybrid Solar Cells

In this work, the development of solution-processed bulk heterojunction hybrid solar cells based on CdSe quantum dot (QD) and conjugated polymer poly [2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b] dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)], PCPDTBT was performed. The photoactive layer was formed by integrating CdSe QDs onto multiwalled carbon nanotubes (CNTs). A simple method of thiol functionalization in the interface CNTs and CdSe QDs has been investigated. Integration of CNTs enhances long-term performance of solar cells devices. Initial PCE values of about 1.9 % under AM1.5G illumination have been achieved for this hybrid CNT-CdSe photovoltaic device. In addition, the long-term stability of the photovoltaic performance of the devices was investigated and found superior to CdSe QD only based devices. About 84 % of the initial PCE remained after storage in a glove box for one year without any further encapsulation. It is concluded that the improvement is mainly due to a strong binding between thiol functionalized CNTs and CdSe QDs, resulting preservation of the nanomorphology of the hybrid film over time.

Regioisomeric π-conjugated terpolymers bearing carboxylate substituted thienothiophenyl quarterthiophene and their application to fullerene-free polymer solar cells

Two regioisomeric π-conjugated terpolymers bearing carboxylated thiophene (CT) as electron accepting unit and thienothiophene (TT) and bithiophene (BT) as electron donating units were successfully synthesized for enhancing the performance of polymer solar cells (PSCs). Regio-regular and regio-random binary copolymers based on CT and BT were also prepared as control polymers. All polymers showed unique optical properties and crystalline behaviors. Among the PSC devices fabricated in this study, the PSC based on the regio-random terpolymer (Ran-TT) and 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:5,6b′]-dithiophene (ITIC) exhibited the highest power conversion efficiency of 5.65% with a high short circuit current density (Jsc) of 12.63 mA cm−2 and an open circuit voltage (Voc) of 0.81 V. The promising PCE value is attributed to the low-lying highest occupied molecular orbital (HOMO) of Ran-TT, effective complementary absorption spectrum and favorable internal morphology of the blend film. The internal morphology of the Ran-TT was observed to be more fine phase separation than that of the regio-regular terpolymer, facilitating exciton diffusion and dissociation in the bulk heterojunction.

Significant impact of monomer curvatures for polymer curved shape composition on backbone orientation and solar cell performances

In the present study, linear or curve-shaped donor units, quinacridone (Qc) and benzo[2,1-b:3,4-b′]dithiophene (BDP), and spacers were introduced for polymerization of four D–A type polymers (PBDPOx-biT, PBDPOx-TT, PQcOx-biT, and PQcOx-TT).The UV–vis absorption spectra of PBDPOx-biT, PQcOx-TT (linear shaped polymer) films were red-shifted compared with the solution absorption, whereas that of a PBDPOx-TT, PQcOx-biT (curve shaped polymer) film was blue-shifted. PBDPOx-biT, PQcOx-TT had high crystallinity. Linear polymers prefer regular and crystalline domains in the film state and lead to more efficient organic photovoltaic (OPV) devices. PQcOx-TT possesses a PCE value of up to 3.4%.

Rational design of cost-effective dyes for high performance dye-sensitized cells in indoor light environments

One of the important features of dye-sensitized solar cells (DSCs) is that their performance is relatively unaffected by lighting conditions, e.g., lighting angles and lighting intensity, which makes them ideal for application in indoor light environments. While most of past research on DSCs has focused on their performance under one-sun conditions, the effect of the structure of the dye on device performance under indoor lights has not been studied before. For this study, we designed a series of organic dyes with donor-π-bridge-acceptor (D-π-A) structure that can be synthesized in three reaction steps from inexpensive raw materials. The photophysical and electrochemical properties of the dyes and the device characteristics of the DSCs employing these dyes under indoor light (LED and T5 lamp, 600 lux) were investigated. In our research, the best PCE value of DSCs under LED lamps was 12.21% when TKU-6 was used as the sensitizer (70.8% of N719). Under T5 lamps, it was 13.43% when TKU-4 was used as the sensitizer (68.5% of N719). Moreover, we proposed the structural design strategies for dyes for high performance DSCs under indoor lights based on the type of π-bridge, the number of alkyl chains and the absorption spectrum of the dye.

DR3TBDTT Based Ternary Blends Containing Conjugated Polymers: Crystallization Determines Morphology and Performance

AbstractHow the conjugated polymers affect the crystallization of DR3TBDTT, in addition to the corresponding morphology and performance, is not well understood. In this work, the weakly crystalline polymer PTB7‐Th and highly crystalline polymers of PCDTBT and P3HT were incorporated into DR3TBDTT:PC71BM system to investigate the variation of crystallization, morphology and performance. It is demonstrated that PTB7‐Th is the most effective additive to improve the PCE value of DR3TBDTT:PC71BM to 5.7%, showing the nucleating agent reducing the crystallization correlation length (CCL) value of DR3TBDTT from 18.7 nm to 17.0 nm, in addition to the optimized morphology. In contrast, the PCDTBT and P3HT could induce the crystallization of DR3TBDTT, leading to much higher CCL value as well as obvious phase separation. Despite of energy level alignment, the crystallization of DR3TBDTT influenced by polymers determines the corresponding morphology of active layers and photovoltaic performance.

Enhancement of photoresponse property of perovskite solar cell by aluminium chloride (AlCl3)

The fabrication of a three layer solar cell device is a new area of research. The formation of perovskite phase is evident from x-ray diffraction and its particle size is observed by microstructural analysis. A thin layer of gold coating over the device increases the surface conductivity. Direct contact between a SnCl2 or AlCl3 based perovskite with the gold coating increases the durability of the film but decreases the hole transport properties due to absence of an organic hole transport material. The absorbance spectroscopy analysis gives characteristic peaks showing the evidence of ITO, TiO2 (rutile) and Sn2+ complexes present in the Sn-perovskite film or Al3+ complexes present within the Al-perovskite cell. The desired absorbance near 550 nm due to Al3+ complexes causes a much higher flow of current on illumination and thus is also evidenced by the presence of comparatively high intensity PL spectra in the Al-perovskite system which occurred due to free exciton formation near band edge excitation. The fill factor of the devices is estimated as ∼0.83 and ∼0.65 for Sn-perovskite and Al-perovskite devices respectively. The PCE values of Sn-perovskite and Al-perovskite devices are calculated 0.39% and 0.96% respectively, which establish Al-perovskite film as a useful component for future solar cell device manufacturing.

Highly crystalline bilayer electron transport layer for efficient conjugated polymer solar cells

Solution processed solar cells are a promising renewable energy technology due to the low fabrication costs. The most commonly used electron transport layer for solution processed organic solar cells is ZnO. However, sol-gel derived ZnO is amorphous, which limits interfacial charge transport. In this study, we demonstrate a ZnO bilayer, composed of a nanoparticle ZnO and sol-gel derived ZnO layer, as the electron transport layer in polymer solar cells incorporating the novel polymer poly [(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3‴-di (2-octyldodecyl)-2,2′; 5′,2″; 5″,2‴-quaterthiophen-5,5‴-diyl)] (PffBT4T-2OD). Compared with the single layer sol-gel ZnO, the bilayer displayed enhanced crystallinity. Consequently, the interfacial transport from the active layer was improved, as evidenced by dark J-V and PL spectroscopy measurements. Solar cells incorporating this bilayer ZnO layer achieved PCE values exceeding 10%, a relative improvement of 25% compared to the sol-gel ZnO devices.

Triphenylamine cored electron-donors for solution-processed organic solar cells: From tri-armed molecules to tetra-armed molecules

A novel tetra-armed D-A type small molecule 4BTF-DTPA-T was designed here by utilizing the thiophene connected ditriphenylamine (DTPA) core and fluorinated benzothiadiazole (BTF) arms. To make a better comparison, tri-armed (star-shaped) 3BTF-TPA was also synthesized. Although a similar absorption spectra covering from 300 to 600 nm was observed for 3BTF-TPA and 4BTF-DTPA-T, much higher extinction coefficient was achieved for tetra-armed 4BTF-DTPA-T in both solution and thin films. Bulk hetero-junction (BHJ) organic solar cells were also fabricated to investigate their photovoltaic performance and as anticipated, a moderate PCE value of 2.61% with a Voc of 1.00 eV was observed in 3BTF-TPA-based solar cells. However, when the tetra-armed 4BTF-DTPA-T was employed as the electron-donors, much enhanced Jsc and FF values up to 9.33 mA/cm2 and 44.80% were achieved for its homogeneous morphology in solar cells, finally leading to the maximum PCE value of 3.68%, indicating that the tetra-armed small molecules could be the promising electron-donors for solution-processed organic solar cells.

Passenger car equivalents of becak bermotor at road segment in Medan

The road traffic systems, travel patterns and other traffic characteristics are different for each country due to differences in the geometric patterns, available transport facilities for commuters, proportional and type of the vehicle itself and so on. In Indonesia, the standard of pce (Passenger Car Equivalent) value found on IHCM (Indonesian Highway Capacity Manual) published in 1997. IHCM stated that the value of pce for heavy vehicles and motorcycles are 1.3 and 0.5 respectively. On these day, regarding Medan as a third biggest city in Indonesia, there have been lot of changes with regarding to the composition of the vehicle, as well as variations of the type of the vehicle itself. Becak bermotor (motorized tricycles) is a vehicle which is widely available in the city of Medan. Data from Medan City Transportation Department stated that there are more than 20,000 motorized motorized tricycles vehicles operating in the city at these day. Pce value of these rickshaws will be calculated based on observations at road and intersections in Medan. The calculation result shows that the pce value of motorized rickshaw is more than 1. This value will make the calculations regarding the performance of the traffic can be performed more accurately.

Carbazole and rhodanine based donor molecule with improved processability for high performance organic photovoltaics

Despite the great potential of carbazole and rhodanine moieties, donor molecule containing carbazole and rhodanine have received less attention because of their limited processability and poor efficiency. In this work, we synthesized a new donor molecule based on a combination of carbazole as a core-unit and rhodanine as an electron-withdrawing end-unit. We introduced diketopyrrolopyrrole as an additional acceptor at a position of π-linker to increase molecular planarity and the overall molecular weight. Our new donor molecule (named LGC-D073) showed a promising PCE value of 6.6% using chlorobenzene as a solvent. Moreover, LGC-D073 exhibited similar performances for both inverted and conventional structures. These results suggest that designing donor molecules with the combination of carbazole and rhodanine can be an efficient new approach to obtain high performance organic solar cells with improved processability.

Efficient and ultraviolet durable planar perovskite solar cells via a ferrocenecarboxylic acid modified nickel oxide hole transport layer.

Planar perovskite solar cells (PSCs) that use nickel oxide (NiOx) as a hole transport layer have recently attracted tremendous attention because of their excellent photovoltaic efficiencies and simple fabrication. However, the electrical conductivity of NiOx and the interface contact properties of the NiOx/perovskite layer are always limited for the NiOx layer fabricated at a relatively low annealing temperature. Ferrocenedicarboxylic acid (FDA) was firstly introduced to modify a p-type NiOx hole transport layer in PSCs, which obviously improves the crystallization of the perovskite layer and hole transport and collection abilities and reduces carrier recombination. PSCs with a FDA modified NiOx layer reached a PCE of 18.20%, which is much higher than the PCE (15.13%) of reference PSCs. Furthermore, PSCs with a FDA interfacial modification layer show better UV durability and a hysteresis-free effect and still maintain the original PCE value of 49.8%after being exposed to UV for 24 h. The enhanced performance of the PSCs is attributed to better crystallization of the perovskite layer, the passivation effect of FDA, superior interface contact at the NiOx/perovskite layers and enhancement of the electrical conductivity of the FDA modified NiOx layer. In addition, PSCs with FDA inserted at the interface of the perovskite/PCBM layers can also improve the PCE to 16.62%, indicating that FDA have dual functions to modify p-type and n-type carrier transporting layers.

Amino-fulleropyrrolidines as electrotropic additives to enhance organic photovoltaics

The synthesis, device fabrication, and electric poling of novel amino-functionalized fulleropyrrolidines in polymer solar cells is reported. Significantly improved device performances and retention stability were achieved with systematic variation in tether length, reaching PCE values in excess of 10%.

Statistical methods and transport modeling to assess PCE hotspots and diffuse pollution in groundwater (Milan FUA)

The Italian law 152/2006 adopted the EU Water Framework Directive principles and delegated to the Regions the task of identifying areas subject to groundwater diffuse pollution. In the Lombardy Plain, the qualitative groundwater conditions are affected mainly by the presence of industries and anthropic activities. The aim of this work was to assess tetrachloroethylene (PCE) diffuse pollution in the Milan Functional Urban Area (FUA), where chlorinated solvents are the main groundwater contaminants and the results of monitoring campaigns for the years 2003-2014 were collected in a dataset. For this purpose, a new methodology was implemented both in a deterministic and stochastic process. At first, hotspots were identified through Cluster Analysis (CA) applied to concentration values collected in unconfined/confined aquifers (2003-14). Then, a numerical transport model was implemented to study the hotspot plume extension in reason to identify monitoring wells not affected by diffuse pollution but related to specific hotspot sources. Consequently, it was possible to erase these data from the whole initial dataset in order to have a new one containing only diffuse concentrations. Interpolating them through ordinary kriging, PCE iso-concentrations maps identified areas where values are over the Maximum Contaminant Level (1.1 μg/l, Italian Law 152/06). Considering descriptive statistics and iso-PCE concentration maps, a median PCE value estimation (10 μg/l) was find as representative of PCE diffuse contamination Milan city. Moreover, a stochastic methodology was used in order to consider uncertainties due to unknown multiple-sources and environmental heterogeneity. The innovative approach gave some interesting solutions to point out areas where the contaminant mass release is higher and where high probability unknown sources can be found.

Novel wide-bandgap copolymer bearing alkylthio-thiophene-substituted benzodithiophene and methyl thiophene-3-carboxylate for highly stable fullerene-free simple polymer solar cells

We successfully synthesized a wide-bandgap p-type copolymer, 3MT-Th-S, bearing alkylthio-substituted benzodithiophene (BDT) as a donor and methyl-3-thiophenecarboxylate (3MT) as a weak electron acceptor. The electron affinity of the sulfur atom in the 2-ethylhexylthio side chains tethered to the thiophene units induces a low-lying highest occupied molecular orbital (HOMO) energy level in the corresponding polymer. 3MT-Th-S displays a strong absorption band from 400 to 600 nm, resulting in a relatively wide optical bandgap. Thin films of 3MT-Th-S exhibit a prominent face-on orientation in the out-of-plane profile, which might be a favorable orientation for moving charge carriers in the vertical direction in polymer solar cells (PSCs). Non-fullerene PSCs based on 3MT-Th-S as the donor and an n-type small molecule (ITIC, ITIC-Me, or IMIDT) were fabricated, and their performance was investigated in detail. Among the PSC devices bearing three different acceptors, the 3MT-Th-S:ITIC-based PSC exhibits the highest power conversion efficiency of 7.86% with a high short-circuit current density of 16.11 mA cm−2 and an open circuit voltage of 0.96 V. The high PCE values of PSC using the as-cast blend films of 3MT-Th-S and ITIC as an active layer without solvent additive are attributed to the low-lying HOMO level of the donor polymer, the complementary absorption behavior of the blend film, the face-on arrangement of polymer chains on the substrate, and the well-formed morphology of the binary blend film. These results clearly demonstrate that 3MT-Th-S is a promising wide-bandgap p-type polymer for high-performance fullerene-free simple PSCs.