Organic Photovoltaic

During the last few decades, and in some cases only the last few years, novel thin-film photovoltaic (PV) technologies such as dye-sensitized solar cells (DSSC), organic solar cells (OPV), and, more recently, perovskite-based solar cells (PSC) have been growing in maturity with respect to device performance and device stability. Together with new material systems, novel device architectures have also been introduced. Both parameters will have an effect on the overall device stability. In order to improve the understanding of degradation effects and how they can be prevented, stress testing under different conditions is commonly applied. By careful combination of stress factors and thorough analysis of photovoltaic parameter decaying curves, an understanding of the underlying degradation pathways can be gained. With the help of standardized and accelerated stress tests, as described in the ISOS-protocols, statements concerning application lifetimes can fi  nally be made and compared among different labs. Once a photovoltaic technology has proven long lasting durability, the ultimate barrier for entering the commercial market are the IEC tests, taking a deeper look on overall safety and reliability, not only on durability. Here, the most prominent stress tests are reviewed, discussed and  ciency, increased device life- extended with respect to learning the most about photovoltaic device stability

This research uses computational simulations using SIESTA (Spanish Initiative for Electronic Simulations with Thousands of Atoms) package based on Density Functional Theory (DFT) to explore the free energies, interaction energies, relative stability, stability of bonds and charge transfer abilities of Organic Photovoltaic (OPV) systems comprising of bis[methano- fullerene(6,6)-phenyl-C61-butyric acid methyl ester] (bisPCBM) as the acceptor and eight different donor polymers. The novel donor polymers are computationally designed based on poly[4,8-bis-substituted-benzo [1,2-b:4,5-b’]dithiophene-2,6-diyl-alt-4-
substituted-thieno[3, 4-b]thiophene-2,6-diyl] (PBDTTT) polymer, the main structural changes being the incorporation of Se and F atoms. From the results it was clear that PCBM makes a wiser choice as the donor compared to bisPCBM for computer simulations. Influence of F atoms was observed in the stability of the system both energetically and structurally. Incorporation of Se negatively affects the feasibility of acceptor-donor interaction.

Polymer:fullerene bulk heterojunction (BHJ) solar cell active layers can be created by traditional blend casting (BC), where the components are mixed together in solution before deposition, or by sequential processing (SqP), where the pure polymer and fullerene materials are cast sequentially from different solutions. Presently, however, the relative merits of SqP as compared to BC are not fully understood because there has yet to be an equivalent (composition- and thickness-matched layer) comparison between the two processing techniques. The main reason why matched SqP and BC devices have not been compared is because the composition of SqP active layers has not been accurately known. In this paper, we present a novel technique for accurately measuring the polymer:fullerene film composition in SqP active layers, which allows us to make the first comparisons between rigorously composition- and thickness-matched BHJ organic solar cells made by SqP and traditional BC. We discover that, in optimal photovoltaic devices, SqP active layers have a very similar composition as their optimized BC counterparts (≈44–50 mass % PCBM). We then present a thorough investigation of the morphological and device properties of thickness- and composition-matched P3HT:PCBM SqP and BC active layers in order to better understand the advantages and drawbacks of both processing approaches. For our matched devices, we find that small-area SqP cells perform better than BC cells due to both superior film quality and enhanced optical absorption from more crystalline P3HT. The enhanced film quality of SqP active layers also results in higher performance and significantly better reproducibility in larger-area devices, indicating that SqP is more amenable to scaling than the traditional BC approach. X-ray diffraction, UV–vis absorption, and energy-filtered transmission electron tomography collectively show that annealed SqP active layers have a finer-scale blend morphology and more crystalline polymer and fullerene domains when compared to equivalently processed BC active layers. Charge extraction by linearly increasing voltage (CELIV) measurements, combined with X-ray photoelectron spectroscopy, also show that the top (nonsubstrate) interface for SqP films is slightly richer in PCBM compared to matched BC active layers. Despite these clear differences in bulk and vertical morphology, transient photovoltage, transient photocurrent, and subgap external quantum efficiency measurements all indicate that the interfacial electronic processes occurring at P3HT:PCBM heterojunctions are essentially identical in matched-annealed SqP and BC active layers, suggesting that device physics are surprisingly robust with respect to the details of the BHJ morphology.

Novel metal free organic dyes coded TET(RA) 4 , TET(CA) 4 , and TET(QA) 4 were designed, synthesized, and characterized as effective sensitizers for dye sensitized solar cells (DSSCs). These new push-pull sensitizers used a strong electron donor consisting of 3,4-ethylenedioxythiophene and two triphenylamine molecules connected together to form a TPA-EDOT-TPA (TET) motif, which is directly connected to tetra anchoring groups (A) without any π-spacers to construct A 2-D-D-D-A 2 architecture, three different anchoring series, viz. rhodanine-3-acetic acid (RA), cyanoacetic acid (CA), and 2-methyl quinoline-6-carboxylic acid (QA) were employed to investigate the influence of anchoring moieties on the electrochemical, thermodynamic, kinetics, and photovoltaic efficiency of DSSCs. The DSSCs devices showed a maximum overall power conversion efficiency (PCE) = 5.13%, short-circuit current density (J SC) = 12.71 mA.cm −2 , open circuit voltage (V OC) = 0.62 V, and fill factor (FF) = 65.36% with a maximum incident photon conversion efficiency (IPCE) = 75% for TET(QA) 4. The optical and electrochemical studies showed that TET(QC) 4 achieved higher electron injection free energy (ΔG°i nj) into CB edge of TiO 2 as well as high recombination resistance (R rec) compared to TET(RA) 4 , and TET(CA) 4 , which explains the outstanding charge separation and superior power conversion efficiency (PCE) of TET(QC) 4 possessing quinoline-6-carboxylic acid (QC) anchoring group. Molecular modeling calculations using DFT and TD-DFT showed effective charge separation, where HOMO is delocalized over the donor scaffold (TPA-EDOT-TPA), and the LUMO is delocalized over only two anchoring groups on the same side of the donor system, which provides strong HOMO-LUMO overlap as well as intimate electronic coupling with TiO 2 nanoparticle surface for electron injection. Further, the calculated values of the energy gaps (E 0-0) and ground/excited stated oxidation potentials were in perfect agreement with the experimental results.

OPV Simulation Tool is an educational resource that predicts the behavior of a bilayer organic solar cell by numerical simulations. By solving the drift-diffusion based transport equations for the flow of excitons, electrons and holes, the OPV Tool calculates the IV curve, the band diagram and the carrier concentration profile, etc. Based on the IV characteristics, the tool also calculates the solar cell performance values such as the efficiency, short circuit current, fill factor, open circuit voltage, etc.

Our program on capacitive energy storage is a comprehensive one that combines experimental and computational components to achieve a fundamental understanding of charge storage processes in redox-based materials, specifically transition metal oxides. Some of the highlights of this program are the identification of intercalation pseudocapacitance in Nb2O5, which enables high energy density to be achieved at high rates, and the development of a new route for synthesizing mesoporous films in which preformed nanocrystal building blocks are used in combination with polymer templating. The resulting material architectures have large surface areas and enable electrolyte access to the redox active pore walls, while the interconnected mesoporous film provides good electronic conductivity. Select first-principles density-functional theory studies of prototypical pseudocapacitor materials are reviewed, providing insight into the key physical and chemical features involved in charge transfer and ion diffusion. Rigorous multiscale physical models and numerical tools have been developed and used to reproduce electrochemical properties of carbon-based electrochemical capacitors with the ultimate objective of facilitating the optimization of electrode design. For the organic photovoltaic (OPV) program, our focus has been ongoing beyond the trial-and-error Edisonian approaches that have been responsible for the increase in power conversion efficiency of blend-cast (BC) bulk heterojunction blends of polymers and fullerenes. Our first approach has been to use molecular self-assembly to create the ideal nanometer-scale architecture using thermodynamics rather than relying on the kinetics of spontaneous phase segregation. We have created fullerenes that self-assemble into one-dimensional stacks and have shown that use of these self-assembled fullerenes lead to dramatically enhanced OPV performance relative to fullerenes that do not assemble. We also have created self-assembling conjugated polymers that form gels based on electrically continuous cross-linked micelles in solution, opening the possibility for water-processable “green” production of OPVs based on these materials. Our second approach has been to avoid kinetic control over phase separation by using a sequential processing (SqP) technique to deposit the polymer and fullerene materials in separate deposition steps. The polymer layer is deposited first, using solvents and deposition conditions that optimize the polymer crystallinity for swelling and hole mobility. The fullerene layer is then deposited in a second step from a solvent that swells the polymer but does not dissolve it, allowing the fullerene to penetrate into the polymer underlayer to the desired degree. Careful comparison of composition- and thickness-matched BC and SqP devices shows that SqP not only produces more efficient devices but also leads to devices that behave more consistently.

Design rules are presented for significantly expanding sequential processing (SqP) into previously inaccessible polymer:fullerene systems by tailoring binary solvent blends for fullerene deposition. Starting with a base solvent that has high fullerene solubility, 2-chlorophenol (2-CP), ellipsometry-based swelling experiments are used to investigate different co-solvents for the fullerene-casting solution. By tuning the Flory-Huggins χ parameter of the 2-CP/co-solvent blend, it is possible to optimally swell the polymer of interest for fullerene interdiffusion without dissolution of the polymer underlayer. In this way solar cell power conversion efficiencies are obtained for the PTB7 (poly[(4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)(3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl)]) and PC61BM (phenyl-C61-butyric acid methyl ester) materials combination that match those of blend-cast films. Both semicrystalline (e.g., P3HT (poly(3-hexylthiophene-2,5-diyl)) and entirely amorphous (e.g., PSDTTT (poly[(4,8-di(2-butyloxy)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl)-alt-(2,5-bis(4,4′-bis(2-octyl)dithieno[3,2-b:2′3′-d]silole-2,6-diyl)thiazolo[5,4-d]thiazole)]) conjugated polymers can be processed into highly efficient photovoltaic devices using the solvent-blend SqP design rules. Grazing-incidence wide-angle x-ray diffraction experiments confirm that proper choice of the fullerene casting co-solvent yields well-ordered interdispersed bulk heterojunction (BHJ) morphologies without the need for subsequent thermal annealing or the use of trace solvent additives (e.g., diiodooctane). The results open SqP to polymer/fullerene systems that are currently incompatible with traditional methods of device fabrication, and make BHJ morphology control a more tractable problem.

The potential of a symmetrical n-hexyl substituted squaraine dye (Sq1) for use as electron donor component in bulk heterojunction organic solar cells (BHJ) with standard and
inverted structure has been studied from optical point of view. The soluble n-type fullerene, (6,6)-phenyl C61 butyric acid methyl ester (PC61MB) was chosen as acceptor. Optical
modeling based on transfer matrix method was carried out to
predict photovoltaic performance of a BHJ device with blended Sq1/PC61MB active layer. It was found out that inverted device stacks show larger calculated maximum short circuit photocurrent (Jsc max) compared to the standard device structure. Modeling of the optical field distribution in the different device stacks proved that this enhancement originates from an increased absorption of incident light in the active layer, and hence from the increased exciton generation rate. Besides, it is also found that the effect of the optical spacer to the increase in Jsc max is less expressed in inverted device stacks than in standard ones.

A new D–A structured conjugated polymer (PBDO-T-TDP) based on electron-rich benzo[1,2-b:4,5-b’] difuran (BDO) containing conjugated alkylthiophene side chains with an electron-deficient diketopyrrolopyrrole (DPP) derivative is designed and synthesized. The polymer shows a narrow band gap with broad UV-Visible absorption spectra, which is in contrast to that of the P3HT:PCBM binary blend. Furthermore, its energy levels can meet the energetic requirement of the cascaded energy levels of P3HT and PCBM. Therefore, PBDO-T-TDP is used as a sensitizer in P3HT:PCBM based BHJ solar cells and its effect on their photovoltaic properties was investigated by blending them together at various weight ratios. It is observed that the resulting ternary blend system exhibited a significant improvement in the device performance (ŋ 3.10%) as compared with their binary ones (ŋ 2.15%). Such an enhancement in the ternary blend system is ascribed to their balanced hole and electron mobility along with uniform distribution of PBDO-T-TDP in the blend system, as revealed by organic field effect transistors and AFM studies.

Carbon nanotubes (CNTs) are hailed as being a "revolutionary super-material", with extensive scope of application, a highly promising one being in Organic Solar Cells (OSCs): ultrathin, ultralight and flexible solar cells with phenomenal applicability and potential. This led us to investigate: "What about their structure, computerised manufacture and function gives CNT OSCs outstanding potential for application in India, what are their economic and environmental benefits and how feasible is their large-scale application in the near future?" Extensive research is done first in their manufacture, wherein the software modeling, machine 3D printing IT System for Si SCs and computerised roll-to-roll piezoelectric inkjet printing used for OSCs are evaluated. Thereafter, the functional science of both SCs is compared (with little difference found). Next, using the LCOE (Levelised Cost of Electricity) method and an interview with a spokesperson from the National Institute of Solar Energy, in depth primary and secondary economic data is collected and compared on running an Si SC and Coal Power Plant with an ideal OSC power system, which shockingly yields OSCs as being even cheaper than coal power! Finally, after discussion on India's grave environmental health and how solar power will help greatly improve that, time until and extent of OSC mass commercialisation and feasibility in India was hypothesized, based on current scientific and developmental progress as well as shortcomings that must be averted prior to this. OSCs are in fact a groundbreaking, lifesaving potential power alternative for India, owing to scope of application, environmental improvements, achieving grid parity, and outstanding reduction in the digital divide and equality of access rampant throughout the nation. It was discovered that while they are arguably the most economical power solution viable, research suggests that they are not to be commercially widespread or even available until at least the coming decade.

A layer-by-layer approach was used for the fabrication of multilayer films for ultra high gas barrier applications. The ultra high gas barrier material was designed by incorporating Nafion layer in between bilayers of poly(ethylene imine) and poly(acrylic acid) on a Surlyn substrate. When the barrier film with self-assembled Nafion is exposed to the moist environment, Nafion absorbs and desorbs water molecules simultaneously, thereby reducing the ingress of moisture in to the film. In order to study the effect of Nafion, the fabricated barrier materials with and without the presence of Nafion were tested for water vapor barrier properties. The barrier films were further used for encapsulating organic photovoltaic devices and were evaluated for their potential use in barrier applications. The devices encapsulated with the films containing Nafion exhibited better performance when subjected to accelerated aging conditions. Therefore, this study demonstrates the effectiveness of self-assembled Nafion in reducing the water vapor permeability by nearly five orders of magnitude and in increasing the lifetimes of organic devices by ∼22 times under accelerated weathering conditions.

Two new low band gap D–A structured conjugated polymers, PBDTTBI and PBDTBBT, based on 2-(4- (trifluoromethyl)phenyl)-1H-benzo[d]imidazole and benzo[1,2-c;4,5-c0]bis[1,2,5]thiadiazole acceptor units with benzo[1,2-b;3,4-b0]dithiophene as a donor unit have been designed and synthesized via a Stille coupling reaction. The incorporation of the benzo[1,2-c;4,5-c0]bis[1,2,5]thiadiazole unit into PBDTBBT has significantly altered the optical and electrochemical properties of the polymer. The optical band gap estimated from the onset absorption edge is _1.88 eV and _1.1 eV, respectively for PBDTTBI and PBDTBBT. It is observed that PBDTBBT exhibited a deeper HOMO energy level (_4.06 eV) with strong
intramolecular charge transfer interactions. Bulk heterojunction solar cells fabricated with a configuration of ITO/PEDOT:PSS/PBDTBBT:PC71BM/Al exhibited a best power conversion efficiency of 0.67%, with a short circuit current density of 4.9 mA cm_2, an open-circuit voltage of 0.54 V and a fill factor of 25%.

Main approaches to the design of organic bulk heterojunction photovoltaic structures are generalized and systematized. Novel photovoltaic materials based on fullerenes, organic dyes and related compounds, graphene, conjugated polymers and dendrimers are considered. The emphasis is placed on correlations between the chemical structure and properties of materials. The effect of morphology of the photoactive layer on the photovoltaic properties of devices is analyzed. Main methods of optimization of the photovoltaic properties are outlined.

Optical and photovoltaic properties were studied for ternary photovoltaic cells containing a traditional donor-acceptor bulk-heterojunction (BHJ) active layer modified with polymethine dye molecules in a broad range of compositions and wavelengths. An effect of composition induced optical transparency, due to the strong modification of the density of states, was observed for symmetrical compositions with approximately equal amount of components. Based on our spectroscopic ellipsometry and atomic force microscopy (AFM) studies we can suggest that the variation of the refractive index, which is significantly reduced in the visible range for ternary systems, is involved in the physical mechanism of the phenomenon. Despite of an addition of the IR absorbing component (which allows broadening of the absorption band to up to 800 nm) no improvement in the power conversion efficiency (PCE) is observed in comparison to the binary BHJ system (P3HT:PCBM). Nevertheless, we believe that further advance of the efficiency will be possible if the energy levels will be chemically designed to avoid formation of charge traps at the BHJ interface during light excitation. Such fine adjustment of the system should become possible with a proper choice of polymer:dye composition due to a high versatility of the polymethine dyes demonstrated in previous studies.

It has been found that the nature of the anion of cationic polymethine dyes in polymer solar cells
affects photoemf. A study of the spectral and luminescent properties has revealed that polymethines in these
cells form contact ion pairs. It has been shown that the difference in behavior between the anions is deter
mined by their ability for photoinduced electron transfer in these pairs.

To optimize the indoor performance of organic photovoltaics (OPVs) with minimized surface recombination, using the appropriate hole-collecting interlayer (HCI) is particularly important because the number of generated charges is much smaller than that under 1-sun condition. In this study, we developed efficient indoor OPVs based on a poly(3-hexylthiophene): indene-C 60 bisadduct photoactive layer by incorporating solution-processed tungsten oxide (WO 3) as the HCI. The performance of the developed OPVs was compared with that of reference OPVs employing a poly(3,4-ethylenedioxythiophene): poly(styrene-sulfonic acid) (PEDOT: PSS) HCI. The new OPVs with WO 3 HCIs exhibited an average power-conversion efficiency (PCE) of 13.0% ± 0.3% under a 1000 lx light-emitting diode, which was slightly higher than the PCE of reference OPVs (12.7% ± 0.2%). The superior indoor performance of WO 3 HCI-based OPVs can be attributed to their more effective hole-collecting and electron-blocking properties associated with the higher work function and lower electron affinity of WO 3 when compared to PEDOT: PSS; these features result in an excellent fill factor (~75%) and a high open-circuit voltage (~0.71 V) for WO 3 HCI-based OPVs. These results demonstrate that inexpensive low temperature-processed WO 3 HCIs can be excellent candidates in OPVs for indoor applications.

Organic dyes can be used as a polar dipole component to create strong local electrical field and promote exciton dissociation in polymer bulk heterojunction (BHJ) solar cells. Some polymethine dyes are characterized with strong IR absorption and therefore can significantly improve light energy harvesting characteristics in such devices due to extension of the absorption spectrum of the photoconducting layer to the IR region. In a view of these opportunities, photovoltaic properties of BHJ systems constituted with poly-3-hexylthiophene (P3HT) as an electron donor, 6,6-phenyl-C61-butyric acid methyl ester (PCBM) fullerene-type electron acceptor, and cation polymethine or merocyanine dyes were studied depending on the dye concentration and under different light excitation conditions. A new physical effect of photoinduced current hysteresis was observed in dye containing BHJ solar cells, when the dye concentration was in the range of 16–60%. The photocurrent hysteresis is detected only when simultaneously polythiophene and dye molecules are excited with light (white light excitation), while no current hysteresis can be seen in the dark or under selective excitation of the polymer component (490 nm) or dye component (740 nm) of the BHJ system. In addition, significant reduction of the photocurrent collected from the dye-containing devices under illumination with white light in comparison to a selective excitation of the polymer component only is observed.

We synthesized a polythiophene with methylbranched side chains, poly(3-2-methylpentylthiophene) (P3MPT), and studied the thermal properties, morphology, optoelectrical properties, and photovoltaic performance of P3MPT blended with the fullerene derivative, [6,6]-phenyl C 60butyric acid methyl ester (PCBM). The results are compared to those of the commonly used poly(3-hexylthiopene) (P3HT) with linear side chains to investigate the effects of the methyl-branched side chain. Differential scanning calorimetry (DSC) shows a higher glass transition temperature, and both X-ray diffraction and UV− vis absorption reveal a lower crystallization rate for P3MPT as compared to P3HT, due to the methyl-branched side chains that more efficiently suppress the chain mobility. Such behaviors can create an optimal as well as a stable structure for bulkheterojunction solar cells so that the P3MPT/PCBM-based device not only shows a higher power conversion efficiency (PCE) but can much more effectively maintain the efficiency with time than the P3HT/PCBM-based device does. The stable phase-separated structure in the P3MPT/PCBM blend is confirmed by the grazing-incidence small-angle X-ray scattering (GISAXS) technique, which explains the superior long-term stability of the P3MPT/PCBM solar cell.

In this research work, significant progress has been achieved to fabricate efficient inverted polymer solar cells (iPSC) using simple and low cost spray pyrolysis (SP) technique to deposit a thin film of ZnO as electron transporting layer (ETL). The deposition parameters of the ZnO films by the SP technique have been studied to obtain the optimal conditions that allow achieving high iPSC's performance. Also, the effect of different thicknesses (number of running cycles) with the SP technique on the iPSC performance has been investigated. Moreover, a standard iPSCs fabricated by spin coating technique has been used as a reference. Four different numbers of running cycles of ZnO were performed, namely, 3R, 5R, 7R and 9R. As the number of running cycles increases the current density of the cells increases and the series resistance decreases. In addition, the 7R-SP iPSCs have showed the best cells performance compared to the others 3R, 5R and 9R samples. At the same time, the performance of the 7R-SP iPSCs were quite similar to the reference samples fabricated by the SC technique. Hence, this promising spray pyrolysis technique might be a breakthrough forward step for the commercialization of inverted polymer solar cell based on mass production as well the probability of improving its efficiency.

The possibilities were studied of improving the photovoltaic performance of solution processed BHJ solar cells by solvent vapor annealing (SVA) of the active layers, based on a squaraine dye Sq1 as a donor and the fullerene derivative PCBM as an acceptor. For this purpose, the optical properties were determined of as-deposited and of annealed with tetrahydrofuran (THF) vapors for different duration Sq1/PCMB layers, as well as the efficiency of cells built on their basis. A considerable change was established in the absorption spectra of treated for only a few seconds films and a twofold increase of the power conversion efficiency after 6 sec SVA. The results obtained are explained in terms of solvent vapor induced phase separation and formation of squaraine dye small aggregates in the blend nanostructure. The assumption made was confirmed by morphological investigation of as-deposited and of annealed Sq1/PCBM blended layers. On this basis, the impact of the active layer nanomorphology on the efficiency of solar cells based on squariane dye as electron donor is discussed.

Photovoltaic properties of the polymer composite films doped with cationic, anionic and neutral polymethine dyes were investigated. It was revealed that the magnitude and even the sign of photovoltaic effect change in going from the free-surface to sandwich structures. It was shown that in free-surface samples the photo-emf sign is determined by the nature of polymer and dye. By contrast, in sandwich structures the photo-emf sign does not depend on composition of the photoactive layer and is governed by drift of the photogenerated charge carriers in the electric field formed by different work function of the electron-and hole-collecting contacts.

A utilização direta da energia solar em elétrica através de placas fotovoltaicas e o surgimento de eficientes baterias de íons de lítio, viabilizando o aparecimento de excelentes carros 100% elétricos, está determinando o limiar entre a era do petróleo e a era das novas cadeias produtivas solares.

Oligothiophenes are used in many applications owing to their easy accessibility in high purity, tunable
electron density, high chemical stability and desired processability in solution and in the solid state. In
this work, a series of soluble branched oligothiophenes have been synthesized and fully characterized.
The target molecules (SCT-1 to SCT-4) are soluble in common organic solvents. Full characterization of
optical and electrochemical properties indicated that the extended p-conjugation led to red-shifts in the
absorption maximum (lmax) from 360 nm (SCT-1) to 440 nm (SCT-4). Fluorescence quantum yields were
in the range of 6–45% for the SCTs. The observed properties of the target molecules are better than the
corresponding linear oligothiophenes. Electron deficient Hg(II) cations interact with electron rich SCT-4
to form a charge-transfer complex which led to significant quenching of photoluminescence in solution.
Moreover, an electron deficient molecule, 7,7,8,8-tetracyanoquinodimethane (TCNQ), also interacts with
electron rich SCTs to form a TCNQ dianion (TCNQ2
). Such conjugated optical materials could be used
for developing potential applications in the near future.

Properties of electrodeposited semiconductor thin films are dependent upon the electrolyte composition, plating time, and temperature as well as the current density and the nature of the substrate. In this study, the influence of the electrodeposition parameters such as deposition voltage, deposition time, composition of solution, and deposition temperature upon the properties of In2S3 films was analyzed by the Taguchi Method. According to Taguchi analysis, the interaction between deposition voltage and deposition time was significant. Deposition voltage had the largest impact upon the stoichiometry of In2S3 films and deposition temperature had the least impact. The stoichiometric ratios between sulfur and indium (S/In: 3/2) obtained from experiments performed with optimized electrodeposition parameters were in agreement with predicted values from the Taguchi Method. The experiments were carried out according to Taguchi orthogonal array L27 () design of experiments (DOE). Approximately 600 nm thick In2S3 films were electrodeposited from an organic bath (ethylene glycol-based) containing indium chloride (InCl3), sodium chloride (NaCl), and sodium thiosulfate (Na2S2O3·5H2O), the latter used as an additional sulfur source along with elemental sulfur (S). An X-ray diffractometer (XRD), energy dispersive X-ray spectroscopy (EDS) unit, and scanning electron microscope (SEM) were, respectively, used to analyze the phases, elemental composition, and morphology of the electrodeposited In2S3 films.