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Made available in DSpace on 2021-06-25T10:27:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-06-01 Wireless communication employing radio-frequency identification (RFID) tags is progressively more widespread in a variety of industrial and commercial sectors. Aspects as demanding specific needs regarding reading distance, production cost, and processability are requested for commercial applications. Nowadays, printing of optical barcodes is the most economically technology for short distance (up to ~30 cm) reading applications. However, the large-scale and low-cost printing of RFID tags would be a competitive alternative to barcode technology because it allows quicker identification with much less reading errors. Here we demonstrate a semi-transparent, screen printed RFID antennas using a non-metallic and environmentally friendly conductive paste. The variation of the film thickness (from 2.5 up to 15 µm) permitted the fabrication of antennas with reading range (0.84–3.29 m), sheet resistance (6.2–36 Ω/sq), and optical transmittance (0–32.3%), which are compatible to commercial or industrial applications aiming short to moderate reading distances. Indústria de Tintas Condutivas TICON Flextronics Instituto de Tecnologia (FIT) Institute of Geosciences and Exact Sciences Department of Physics São Paulo State University (Unesp) Institute of Geosciences and Exact Sciences Department of Physics São Paulo State University (Unesp)

Made available in DSpace on 2019-10-06T17:10:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01 Conductive composites based on cross-linked poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) blends have been widely applied to produce electronic devices, such as organic electrochemical transistor, biosensors and electrochromic devices, to name a few. Notwithstanding, fundamental details regarding the influence of the cross-link agent on the charge transport mechanism of PEDOT:PSS based composites is still not completely understood. Herein, we present a study regarding the influence of the cross-link (3-glycidyloxypropyl) trimethoxysilane (GPTMS) on the charge transport mechanism of PEDOT:PSS/GPTMS composites. We have verified that the charge transport is dominated by hopping into percolated PEDOT:PSS-rich clusters for composites with a PEDOT:PSS content above 40%-wt. Interestingly, by analyzing the conductivity data by the variable range hopping model we observed that the hopping temperature, electronic localization length and charge carriers mobility remains practically independent on the PEDOT:PSS concentration. As for non-percolated composites, (i.e. below 40%-wt PEDOT:PSS), however, the charge transport is dominated by charge carrier hopping between unconnected PEDOT:PSS clusters, in which the electrical conductivity and the hopping temperature are strongly influenced by the cross-link agent content, and characterized by shorter carrier localization lengths. Physics Department Institute of Geosciences and Exact Sciences São Paulo State University – UNESP Sao Carlos Institute of Physics University of São Paulo, PO Box 369 Physics Department Institute of Geosciences and Exact Sciences São Paulo State University – UNESP

Zinc oxide (ZnO) is a n-type transparent semiconductor which can be processed by low cost techniques (such as spray-pyrolysis and spin-coating) and can be applied as the active layer of thin-films transistors (TFTs). The electrical properties of ZnO films are strongly affected when the device is exposed to room conditions and/or UV-light, suggesting possible applications as UV or/and gas sensors. Atmospheric oxygen molecules adsorbed on ZnO surface act as charge traps, decreasing the material conductivity. The incidence of UV-light causes an increase of the material conductivity due to the photogeneration of electron-hole pairs via direct band-to-band transitions (classic photoconductivity process) and due to the desorption of oxygen molecules, which presents a relatively slower response and is a less understood mechanism. In the current paper, we study the influence of environmental parameters, such as temperature, humidity and UV-light intensity, on the electrical properties of spin-coated ZnO thin films to understand the role of the desorption mechanism on the photoconductivity process. The analysis of the device current vs. time curves shows the existence of two light-induced desorption mechanisms: i) one which increases the electrical conductivity of the ZnO film (desorption-like process) and ii) a second one which decreases the conductivity (adsorption-like process). A Plackett-Burman design of experiment (DOE) was used to study the influence of characterization factors like UV intensity, temperature and humidity on electrical parameters obtained from the experimental curves. We observed that the desorption-like process is a first order mechanism, exhibiting desorption rate proportional to n(t), where n(t) represents the adsorbate concentration as a function of the time, whereas the adsorption-like mechanism exhibits a desorption rate proportional to the forth power of n(t).

Made available in DSpace on 2020-12-12T01:53:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-04-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Polymer light-emitting electrochemical cells (PLECs) are organic electronic devices which operating mechanism depends on the injection and transport of electronic charge carrier and the electrochemical doping of the organic semiconductor. The details of the interactions between the salt (or its ions) and the semiconducting polymer composing the device active layer provide important information about the electronic processes associated to the device operation in steady-state. In this context, the present paper proposes a study where theoretical results from Density Functional Theory (DFT) were obtained for three different steady-state operational regimes: i) without external voltage, in which the undissociated salt molecules interact with uncharged semiconducting polymer; ii) for applied voltages lower than the device turn-on (VEg/e), in which the dissociated ions interact with charged semiconducting polymer. In addition, the theoretical results have been confronted with experimental results of PLECs fabricated using different salt concentrations. For both theoretical and experimental approaches, we considered lithium triflate as the salt compound and poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-vinylenephenylene)] (F8PV) as the semiconducting polymer. We observed substantial changes in the electronic structure of the systems at the different operating regimes, which were interpreted in terms of the electronic charge injection from the electrodes and the electrochemical doping of the semiconducting polymer. São Paulo State University (UNESP), Posmat São Paulo State University (UNESP) Institute of Geosciences and Exact Sciences Physics Department University of São Paulo São Carlos Institute of Physics, São Carlos São Paulo State University (UNESP) School of Sciences Physics Department São Paulo State University (UNESP) Campus of Itapeva São Paulo State University (UNESP), Posmat São Paulo State University (UNESP) Institute of Geosciences and Exact Sciences Physics Department São Paulo State University (UNESP) School of Sciences Physics Department São Paulo State University (UNESP) Campus of Itapeva CNPq: 133770/2017-6 FAPESP: 2007/58991-1 FAPESP: 2013/24461-7 FAPESP: 2014/20410-1 CAPES: 23038.004680/2015-01 CNPq: 420449/2018-3 CNPq: 448310/2014-7

Made available in DSpace on 2020-12-10T20:06:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Recent studies have shown spray-pyrolysis is a low-cost, simple and efficient technique for deposition of metal oxide semiconductors (such as zinc oxide) as the active layer of thin-film transistors (TFTs). However, to allow the translation from laboratory scale to industry the reproducibility of such method needs to be evaluated. We present herein a representative study concerning the reproducibility and uniformity of spray-coated ZnO TFTs using several devices, from different production batches, following the same fabrication protocol. We demonstrate that it is possible to obtain transistors with high performance and reproducibility by controlling the most relevant deposition factors, corroborated by a low deviation rate (below 10%) from the characteristic TFT parameters (mobility in saturation, threshold voltage and on/off ratio), which is compatible to commonly available commercial electronic devices. Sao Paulo State Univ UNESP, Phys Dept IBILCE, BR-15054000 Sao Jose Do Rio Preto, SP, Brazil Sao Paulo State Univ UNESP, Phys Dept IGCE, Av 24A,1515, BR-13506900 Rio Claro, SP, Brazil Sao Paulo State Univ UNESP, Phys Dept IBILCE, BR-15054000 Sao Jose Do Rio Preto, SP, Brazil Sao Paulo State Univ UNESP, Phys Dept IGCE, Av 24A,1515, BR-13506900 Rio Claro, SP, Brazil FAPESP: 2019/08019-9 CAPES: 001

In the present study, we analyze the influence of temperature and active layer thickness on the electrical properties of electroluminescent devices comprising a polymeric conductive blend (poly(3,4 ethylenedioxythiophene):polystyrene sulfonate, PEDOT:PSS), an inorganic electroluminescent material (manganese doped zinc orthosilicate, Zn2SiO4:Mn) and an organosilicon material (3-glicidoxypropyltrimethoxysilane, GPTMS), manufactured at different weight ratios of the component materials. The devices were obtained by depositing the active layer by drop-casting onto ITO-coated (RF-sputtering) glass substrates and thermally evaporating gold top electrodes in high vacuum. The results show that 90 wt% Zn2SiO4:Mn is required to observe high electroluminescence from the fabricated devices and that the optimum performance (turn-on voltage of 33 V, luminous efficacy of 24 cd/A and maximum luminance of almost 2000 cd/m2) was achieve for a (9.5/0.5/90) (GPTMS/PEDOT:PSS/Zn2SiO4:Mn) weight ratio. The device turn-on voltage found to be as proportional to the thickness of the active layer, indicating that the electroluminescence occurs by a field-effect mechanism. The temperature variation in the 100–300 K range allowed us to develop a theoretical model for the device operation, where the charge carrier transport in the active layer is well described by the variable range hopping model, with luminous efficacy nearby independent of the temperature.

Metal oxides like zinc oxide (ZnO) are promising materials for the active layer of thin-film transistors (TFTs) used in the drive circuit of next-generation large-area active matrix displays due to their high electronic mobility, high transmittance in the optical visible range and processability. Traditional deposition techniques employ RF sputtering or pulsed-laser deposition (PLD), which are relatively sophisticated techniques. The deposition of very thin (less than 50 nm thick) layers of ZnO using soluble organic precursors have been extensively investigated recently as an alternative to traditional deposition methods. Solution-based deposition processes include simple and affordable techniques like dip-coating, spin-coating, spray-pyrolysis and ink-jet printing. Spray-pyrolysis is particularly interesting due to the high film uniformity, low cost and high device performance. We carried out several experiments analyzing the performance of ZnO based devices using zinc acetate as organic precursor to confirm that spray pyrolysis deposition is a suitable technique for production of high-performance and reproducible TFTs. Moreover, we observed that device performance can significantly vary with little modifications on the deposition parameters, even for the same active layer composition and pyrolysis temperature. Electrical parameters, as the electrical mobility and the on/off ratio, varied several orders of magnitude, whereas the threshold voltage varied up to 20 V for the tested devices. Deposition parameters as the nozzle height during the deposition, nozzle air pressure and deposition time were varied until we obtained devices with optimum electrical performance. Optimized devices presented mobilities in the order of 1 cm2.V-1.s-1, on/off ratio of about 106 and relatively low operation voltages. A statistical analysis of a great number of devices manufactured using the same deposition parameters was also carried out to assure the reproducibility of the deposition technique.

In the current work, we evaluate the influence of the processing parameters on the electrical properties of aluminium zinc oxide (AZO) thin films produced by airbrush spray-pyrolysis deposition technique. Spray-deposited AZO thin-films were produced with Al:Zn molar ratios varying from 0 % (pure ZnO) up to 30 %, using aluminium acetate and zinc acetate as organic precursors and water as solvent. Thermogravimetric analysis (TGA) and infrared spectroscopy (FTIR-ATR) were used to monitor the metal-oxide formation from the organic precursors as a function of the temperature. The results show that a temperature of 400 °C is necessary to completely degrade the organic phase and to obtain the desired inorganic metal-oxides films. The electrical properties of the TMOs were evaluated by d.c. current-voltage (I-V) analysis using planar thermally evaporated Al electrodes on top of the TMO layer, with different aspect ratios (1/18, 2/9, 5/13, 5/9 and 8/9). The lowest sheet resistance was obtained for AZO films at a molar Al concentration of 5 %. We also observed that, after carrying out a post-annealing treatment (30 mbar, 150 °C) the samples presented a decrease on the sheet resistance superior to 60 %, in comparison to the samples before the treatment.

Made available in DSpace on 2019-10-06T16:38:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-01-01 Thin-film transistors (TFTs) with the active layer composed by zinc oxide (ZnO) deposited via spray-pyrolysis present several advantages such as high electrical performance, high optical transmittance in the visible spectrum, low production cost and the ability to cover large areas. Besides the traditional application in electronic/optoelectronic circuits, ZnO TFTs can also be used in sensing devices due to its responsivity to UV-light. In the present work, we performed a bi-level full multifactorial analysis of TFT performance parameters exposed to UV-light. Characterization conditions like UV-light irradiance and time after UV exposure, as well as processing parameters such as annealing temperature were varied simultaneously, allowing the application of analysis of variance (ANOVA) to investigate the effect of these factors on the electrical performance of the devices. Field-effect mobility, threshold voltage, on/off current ratio and the device intrinsic current were among the parameters used as the responses in the factorial analysis. ANOVA was used to determine the ranking of significance of each factor on the different response parameters by the evaluation of the factor effects. Moreover, the results from ANOVA permitted the construction of linear functions used to predict the device responses in the whole range of the experimental conditions, which were confirmed by independent experimental results. The influence of factor interactions and of the linearization of some response parameters was also studied to improve the accuracy of TFT response prediction. Physics Department/IBILCE UNESP – São Paulo State University Physics Department/IGCE UNESP – São Paulo State University, Av. 24A, 1515 Physics Department/IBILCE UNESP – São Paulo State University Physics Department/IGCE UNESP – São Paulo State University, Av. 24A, 1515

Made available in DSpace on 2018-12-11T17:02:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-08-01 We present a study of the electrical properties of electrochemically doped conjugated polymers using polymeric light-emitting electrochemical cells (PLECs) and interpreting the results according to a phenomenological model (PM) which assumes that, above the device turn-on voltage, the bulk transport properties of the doped organic semiconductor are responsible for the main contribution to the whole device conductivity. To confirm the predictions of this model, the dependence of the conductivity of PLECs with different parameters is evaluated and compared with the behavior expected for a doped semiconducting polymeric material. The organic semiconductor doping level, the blend concentration of organic semiconducting molecules, the device thickness, the charge carrier mobility, and the temperature are the parameters varied to perform this analysis. We observed that the device conductivity is independent of the active layer thickness, weakly dependent on the temperature, but strongly dependent on the semiconductor doping level, on the semiconductor fraction in the blend, and on the intrinsic charge carrier mobility. These results were well described by the variable range hopping (VRH) model, which has been widely employed to describe the charge transport in doped semiconducting polymeric materials, confirming the prediction of the phenomenological model. The current analysis demonstrates that PLECs are a suitable system for studying, in situ, the electrochemical doping of semiconducting polymers, permitting the evaluation of material properties as, for instance, the density of electronic charge carriers (and, consequently, the ionic charge carrier concentration) necessary to achieve the maximum electrochemical doping level of the organic semiconductor. Departamento de Física Instituto de Geociências e Ciências Exatas Universidade Estadual Paulista – UNESP Instituto de Física de São Carlos Universidade de São Paulo Departamento de Física Instituto de Biociências Letras e Ciências Exatas Universidade Estadual Paulista – UNESP Departamento de Física Instituto de Geociências e Ciências Exatas Universidade Estadual Paulista – UNESP Departamento de Física Instituto de Biociências Letras e Ciências Exatas Universidade Estadual Paulista – UNESP

Solution-processed zinc oxide (ZnO) thin-film transistors (TFTs) obtained via hydrolysis/pyrolysis of an organic precursor present an excellent technique to obtain high performance electronic devices with low manufacturing cost. In the current work, we propose the use of an alternative deposition method, based on a polymeric precursor route (known as Pechini), to obtain solution-processed ZnO compact films as the active layer of TFTs. The elimination of the organic phase and the formation of inorganic thin-films was carried out by thermal treatment at different temperatures (ranging from 200oC to 500oC) and at different times (from 5 min to 2 hours), being monitored by UV-vis and infrared (IR) optical absorption spectroscopy. It was observed that, for temperatures above 400oC and treatment times superior to 30 min, the organic phase was completely eliminated, remaining only the inorganic (metal oxide) phase. The optical bandgap of the resulting ZnO films, determined from UV-vis absorption, is about 3.4 eV. The electrical characteristics (output and transfer curves) of the obtained devices demonstrate the feasibility of Pecchini method to build solution-processed metal oxide TFTs. The results for the electrical mobility of the majority charge-carriers (electrons) and for the threshold voltage were 0.39 cm2.V-1.s-1 and 0.45 V, respectively.

Made available in DSpace on 2020-12-12T02:43:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-09-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) In this work, we employed impedance spectroscopy measurements to investigate the electrical properties of hybrid films obtained with the sol-gel process using 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetraethylorthosilicate (TEOS) at different GPTMS/TEOS molar ratios and temperatures of thermal treatment. For the GPTMS/TEOS-derived samples with 1:1 composition, the DC conductivity (σdc) and charge carrier mobility (μdc) increased linearly with heat treatment temperature from 25 to 80 °C, while σdc increased from 3.2 to 22.4 nS/cm with a 7-fold increase in the GPTMS concentration. These results could be rationalized with the Miller-Abraham model using a charge carrier activation energy of 0.54 ± 0.03 eV. Using FTIR spectroscopy we demonstrated that the structural arrangement of the hybrid matrix involves epoxy ring opening, thus favoring proton conduction, which occurs as in the Grotthuss mechanism via hopping between nearest oxygen atoms of polymerized glycidoxypropyl groups. It is significant that electrical properties of organic/silica matrices can be predicted and tuned for tailored applications using the modeling presented here. Department of Physics Sao Paulo State University (UNESP) Institute of Geosciences and Exact Sciences Sao Carlos Institute of Physics University of Sao Paulo (USP), CP 369 Department of Physics Sao Paulo State University (UNESP) Institute of Geosciences and Exact Sciences FAPESP: 2011/18149-5 FAPESP: 2013/14262-7 CNPq: 427220/2018-1 CNPq: 444810/2014-5

Made available in DSpace on 2018-12-11T17:36:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-07-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) A number of solution-processed electronic materials have been developed for application in printed devices, which are normally built by piling up several coated layers one on the top of the other. To achieve low-cost and simple to manufacture printed devices, stable and easy to process layers are mandatory. Here we introduce a mixture of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) with 3-glycidoxypropyltrimethoxysilane (GPTMS) as solution-processed material that becomes insoluble in water after film processing. We performed morphological, optical and electrical characterization in the proposed composite and highlight its advantages as a stable transparent electrode in light-emitting diodes as well as in electrochromic devices. Physics Department Institute of Geosciences and Exact Sciences São Paulo State University – UNESP Sao Carlos Institute of Physics University of São Paulo, PO Box 369 Brazilian Synchrotron Light Laboratory (LNLS) Brazilian Center for Research in Energy and Materials (CNPEM), Campinas Physics Department Institute of Biosciences Language and Exact Sciences São Paulo State University – UNESP Physics Department Institute of Geosciences and Exact Sciences São Paulo State University – UNESP Physics Department Institute of Biosciences Language and Exact Sciences São Paulo State University – UNESP CAPES: 2015/25069-9 FAPESP: 312025/2016-5

This paper describes a theoretical model which takes into account charge injection by thermally stimulated hopping (HP), as proposed by Arkhipov, and Fowler–Nordheim tunneling (FNT), for steady-state response of a metal/organic semiconductor hetero-junction in a polymeric light-emitting diode (PLED). The reason for combining these two models is that both injection processes are usually observed in metal/organic semiconductor hetero-junctions. The present model takes into account the material disorder and the escape probability introduced by Arkhipov et al. for both injection processes. The proposed model was tested with experimental results obtained from a PLED ITO/MEH-PPV/Al. Analysis of the experimental results took into account the well-known characteristic of the MEH-PPV in which the charge transport is dominated by holes. Because of this, the electronic current component is assumed to be negligible compared to that for holes. Considering that the device is composed of two different metal/semiconductor junctions, that is, ITO/MEH-PPV and MEH-PPV/Al, the heights of the different potential barriers could be determined. The injection potential barrier, for holes, was determined as 0.4 eV for direct bias (ITO as anode), and as 0.8 eV for reverse bias (aluminum as anode). It was verified that the FNT process is preferable to the HP process in the following situations: (i) high interface potential barrier, (ii) high electric field, and (iii) low temperatures. On the other hand, that is, for a low interface potential barrier, low electric field and high temperatures, the HP process is dominant. With the application of the proposed model, which combines HP and FNT, it was possible to fit the current versus voltage curves for the studied PLED in a wide range of temperatures and electric fields, for direct and reverse bias. Additionally, it was shown that the condition where the HP injection probability is neglected, the non-linearity in FNT plots, versus , obtained experimentally by several authors, may be a consequence of the material disorder. When the HP process is associated with the FNT a more significant non-linearity in the FNT plot was verified.

article i nfo Article history: Understanding and controlling charge transport are crucial to achieve optimized organic devices, including light emitting diodes. In this study, we investigate the charge injection in devices made with a hybrid composite (HC) containing Zn2SiO4:Mn (ZSP:Mn) in a polymeric blend consisting of poly(o-methoxyaniline) (POMA) and poly(vinylidene co-trifluorethylene) P(VDFTrFE), with the architecture ITO/HC/metallic electrode (ME). Charge injection was found to depend mainly on the POMA semiconducting phase. For ITO/HC/Au, an Ohmic junction was observed because the work function of ITO is close to that of Au, which also matches the energy levels of HC. Holes are injected through the HC/Au junction, as the highest occupied molecular orbital (HOMO) level of POMA matches the Fermi level of Au. The impedance spectroscopy data for the ITO/HC/ME devices were analyzed with a theoretical model where charge injection was assumed to occur via hopping with a distribution of potential energy barriers. The average hopping distance was estimated as 5.5 A and only the device with the Al electrode had the current limited by the interface mechanism (charge injection). For ITO/HC/Cu and ITO/HC/Au devices the limiting factor for the charge transport was the bulk resistance of the samples, in spite of the existence of a small interface energy barrier. The disorder parameter was 0.18 and 0.19 for the HC/Cu and HC/Al interfaces, respectively, which arises from the disordered nature of the hybrid material. The combination of the Cole-Cole model and the Miller-Abrahams function are a good approach to describe charge a.c. injection processes in disordered materials.

We report on light-emitting devices based on a green-phosphor compound (Mn-doped zinc silicate, Zn2SiO4:Mn) dispersed in a conductive polymeric blend (poly-o-methoxyaniline/polyvinylene fluoride, POMA/PVDF-TrFE). The devices exhibited high luminance in the green, good stability and homogeneous brilliance over effective areas up to 5 cm2. The electroluminescence (EL) spectrum presented essentially the same characteristics as the photoluminescence (PL) and cathodoluminescence spectra, indicating that the light emission originates from decay of the same excited species, regardless of the excitation source. Operating characteristics were analyzed with current density–voltage (J–V ) and luminance–voltage (L–V ) curves to investigate the nature of the electroluminescence of the active material, which is still not completely understood.

Made available in DSpace on 2018-11-26T16:16:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-03-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) INEO nBioNet, Brazil In this study we propose the use of a blend, comprising poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) and polyvinyl alcohol (PVA), to be used as flexible, semitransparent and highly conductive material for electronic and optoelectronic devices. The electrical conductivity and optical transmittance of spray-deposited films of the blend, in different thicknesses and at different weight ratios, were studied in order to determine the most appropriate composition for optimal device performance and cost. We propose a direct method to determine the most appropriate blend composition to produce polymeric films with a desired sheet resistance, optical transmittance and cost, by using a diagram which considers the influence of blend composition and film thickness in a light-transmittance versus sheet resistance plot, mediated by the material cost per unit area. In this way, the present study establishes an empirical method to determine the PEDOT: PSS/PVA blend composition to be used as electrode material in optoelectronic devices which satisfies the desired conditions of optical transmittance, sheet resistance and cost-effectiveness. Univ Estadual Paulista UNESP, Dept Fis, BR-13506900 Rio Claro, Brazil Univ Estadual Paulista UNESP, Dept Fis, BR-15054000 Sao Jose Do Rio Preto, Brazil Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560250 Sao Carlos, SP, Brazil Univ Estadual Paulista UNESP, Dept Fis, BR-13506900 Rio Claro, Brazil Univ Estadual Paulista UNESP, Dept Fis, BR-15054000 Sao Jose Do Rio Preto, Brazil FAPESP: 2008/57706-4 FAPESP: 2012/19005-0 FAPESP: 2012/01624-5

A phenomenological model has been developed to account for the results of impedance/admittance spectroscopy measurements from light-emitting electrochemical cells (LECs) comprising a polymer electrolyte and two different conjugated polymers used as organic semiconductor. The application of a d.c. offset bias superimposed to the a.c. modulation voltage was used to observe the transition from the behavior prior to device operation and after the formation of the electrochemical p-i-n junction. The analysis of the whole device “conductivity” as a function of the applied bias and of the frequency was used to support the assumptions considered to develop the model. The results show that the device, after the p-i-n junction formation, can be considered as composed by two highly conductive electrochemically doped (n and p) regions and a thin (few tens nanometers), insulating layer, where the electrical current is dominated by electronic charge carrier injection via tunneling through a rectangular energy barrier. Before the p-i-n junction formation, there is no doping of semiconductor material, and the device electrical properties are dominated by the intrinsic electronic charge carriers in the organic semiconductor. Results from devices made of organic semiconductors with different band gap energy and different layer thicknesses are used to corroborate the proposed model.

Células eletroquímicas poliméricas emissoras de luz, PLECs, são dispositivos eletrônicos orgânicos que vêm despertando muito interesse comercial por operarem sob baixa tensão com alto desempenho e sem a necessidade de eletrodos específicos, como o óxido de estanho e índio (ITO), cálcio entre outros. Esta característica confere a possibilidade de processamento de baixo custo e de obter dispositivos flexíveis. Nas PLECs a injeção de portadores eletrônicos de carga nas interfaces, entre a camada ativa do dispositivo e seus eletrodos, é facilitada por ação de espécies iônicas, que são inseridas no material polimérico por adição de um sal. Do ponto de vista científico, o interesse atual reside na completa compreensão dos fenômenos de transporte de portadores eletrônicos no interior do dispositivo. Hoje existem dois modelos concorrentes. Um considera o transporte eletrônico por difusão e o outro leva em consideração a dopagem eletroquímica e a consequente formação de uma junção PIN (semicondutor dopado tipo-p camada isolante semicondutor dopado tipo-n). Nesse contexto, propusemos a fabricação e caracterização elétrica de PLECs com diversas composições e espessuras a fim de confrontar os resultados experimentais com os modelos em questão. Demonstramos a existência de uma concentração crítica de sal, abaixo da qual a operação da PLEC é promovida predominantemente por injeção auxiliada pela formação de duplas-camadas devido ao movimento iônico. No regime de tensões mais elevadas, além da injeção, ocorre a dopagem tipo-p e tipo-n e a formação da junção PIN. Além disso, determinamos que para tensões superiores à de operação o dispositivo apresenta comportamento ôhmico, com resistência elétrica proporcional à espessura do dispositivo e praticamente independente da temperatura. Nossos resultados mostraram que no regime de tensões mais baixas deve ocorrer um processo de transporte por difusão, mas à medida que a tensão aumenta, inicia-se um processo de dopagem tipo-p de um lado e tipo-n de outro, aumentando a condutividade das regiões dopadas e finalizando com a formação de uma junção PIN. Mostramos também que a tensão acumulada nas duplas-camadas independe do tipo de polímero eletrônico, e que a tensão de operação, aquela na qual o polímero luminesce, é semelhante á do gap da banda proibida do polímero luminescente. Polymer light emitting electrochemical cells, PLECs, are organic electronic devices that have attracted commercial interest because they operate at low voltage and exhibit high performance without the need of specific electrodes such as indium tin oxide (ITO), calcium and others. This feature provides low cost of fabrication and exible devices. The charge injection in the PLECs is facilitated by the action of ionic species, which are inserted in the polymeric material by adding a salt. This thesis treats with a controversy related to transport phenomena along the bulk of the device. Currently, there is two opposite models. One that considers that transport is driven by diffusion mechanism; and the other takes into account the formation of a PIN junction (p-type semiconductor insulating layer n-type semiconductor). Here, we proposed the fabrication and characterization of PLECs having different compositions and thickness, and the results were faced up to the models. We showed the existence of critical concentration of salt, below of which the operation of the PLECs are mainly due to injection stimulated by the ionic double-layer. For higher applied voltages, the injection still exists but it is followed by a PIN junction formation. We also verified that for voltages above the turn-on the device electrical resistance is proportional to the sample thickness and is practically temperature-independent. Our results showed that for low voltages the transport is dominated by diffusion, but as the voltage increases, the semiconducting layer starts to be doped: p-type in one side, and n-type in the other. Therefore, the conductivity of the semiconducting layer increases, and it finalizes by the formation of the PIN junction. Finally, we showed that the double-layer characteristic does not depend on the electronic polymer, and that the value of the turn-on voltage is very close to that of the electronic gap of the forbidden band.

Dispositivos poliméricos emissores de luz (Polymer Light Emitting Diodes - PLEDs) têm sido amplamente investigados devido à sua possibilidade de aplicação na fabricação de telas de projeção e displays. As principais vantagens dos materiais poliméricos, nesses casos, são o baixo custo e a possibilidade de processamento em superfícies de grande área, ao contrário do que ocorre para dispositivos contendo cristais líquidos (Liquid Crystal Display - LCD\'s). Apesar de amplamente investigados nos últimos anos, alguns aspectos fundamentais acerca dos mecanismos de injeção de carga nos PLEDs ainda não estão completamente elucidados. Nesta dissertação estudamos as propriedades ópticas, morfológicas e elétricas de dispositivos poliméricos emissores de luz contendo poli(2-metóxi, 5-(2\'-etil-hexilóxi)-1,4-fenileno vinileno) (MEH-PPV) como camada ativa. Inicialmente foi investigada a influência de camadas transportadoras de lacunas (Hole Transport Layer - HTL) e/ou elétrons (Electron Transport Layer - ETL) na eficiência dos dispositivos. As camadas HTL e ETL foram compostas de poli(3,4-etilenodioxithiofeno):poliestireno sulfonado (PEDOT:PSS), e poli(estireno-co-p-estireno sulfonado-co-metaacrilato de metila) (PS-co-SS-co-MMA), respectivamente. Os filmes de PEDOT:PSS foram depositados por centrifugação. Devido ao seu caráter isolante (condutividade elétrica 10-5 S/cm), e por ter nível energético HOMO (Highest Occupied Molecular Orbital) próximo ao nível de Fermi do ITO (Indium Thin Oxide), a utilização do PEDOT:PSS como camada reguladora da injeção de lacunas resultou num aumento do tempo de meia vida do dispositivo em cerca de 10 vezes. No caso de dispositivos contendo a camada de ETL, foi identificada a formação de estados localizados gerados pela sulfonação do poliestireno. Estes estados auxiliam no processo de tunelamento através da camada polimérica. Na segunda parte do trabalho, apresentada no capítulo 4, desenvolvemos um modelo teórico para descrever as regiões das curvas da densidade de corrente elétrica (J) vs. campo elétrico aplicado (F) (dependentes e independentes da temperatura). Este modelo é uma extensão do modelo de Arkhipov, onde inserimos um termo de injeção de carga via tunelamento Fowler-Nordhein através de uma distribuição gaussiana de barreiras de potencial de interface, além do termo de injeção via hopping, já tratado por Arkhipov. O modelo proposto ajustou satisfatoriamente as curvas de J vs. F tanto nos modo de polarização direta, quanto reversa. Polymer light emitting diodes (PLEDs) have been widely investigated as candidate materials for display fabrication. The main advantages exhibited by PLEDs are the low-cost processing and possibility of large-area display fabrication, in comparison to the conventional liquid crystal displays (LCD\'s). Although the engineering aspects concerning device fabrication and characterization are well understood, some specific points regarding the electrical transport in the bulk and at the interfaces of the devices are not fully explained. In this study, we present a morphological, optical and electrical characterization of PLEDs containing poly(2-methoxi, 5-(2\'-etyl-hexiloxy)-1,4-phenilene vinilene) (MEH-PPV) as the emissive layer. We investigated the influence of hole transport layers (HTL) and/or electron transport layers (ETL) on the efficiency of the devices. The HTL and ETL comprised thin polymeric films of poly(3,4-etylenedioxythiphene):sulfonated polystyrene (PEDOT:PSS) and poly(estyrene-co-p-sulfonated styrene-co-metyl metacrylate) (PS-co-SS-co-MMA), respectively. Devices containing the PEDOT:PSS exhibited a life-time 10 times higher than the devices not containing the HTL material, which is probably due to the controlled hole injection that may be achieved in former devices. In the second set of devices, in which an ETL was incorporated, we observed the formation of localized states in the polymeric ETL layer, which was responsible for improving the tunneling process of charges injected from cathode. A theoretical model concerning the charge injection mechanisms in the PLEDs containing MEH-PPV is presented in chapter 4. The final device architecture was ITO/MEH-PPV/Al, and the J vs. F measurements were taken at temperatures between 120 K and 270 K. The model proposed here is a combination of the Arkhipov´s and Fowler-Nordhein tunneling models, considering a Gaussian distribution of triangular potential barriers. The model takes into account the charge carrier/image charge recombination probability at the interface of the electrode, being very appropriate to explain the dependence of the electric current on the temperature and applied electric field.

The phase transition from the non-polar /spl alpha/-phase to the polar /spl beta/-phase of poly(vinylidene fluoride) (PVDF) has been investigated using micro-Raman spectroscopy, which is advantageous for being a non-destructive technique. Films of a-PVDF were subjected to stretching under controlled rates and at 80 /spl deg/C, the transition to /spl beta/-PVDF being monitored by the decrease in the Raman band at 794 cm/sup -1/ characteristic of the /spl alpha/-phase, with the concomitant increase in the 839 cm/sup -1/ band characteristic of the /spl beta/-phase. Poling with negative corona discharge was found to affect the a-PVDF morphology improving the Raman bands related to this crystalline phase. This effect is minimized for films stretched to higher ratios. Significantly, corona-induced effects could not be observed with the other experimental techniques, viz, X-ray diffraction and infrared spectroscopy.

Understanding the microscopic origin of the dielectric properties of disordered materials has been a challenge for many years, especially in the case of samples with more than one phase. For polar dielectrics, for instance, the Lepienski approach has indicated that the random free energy barrier model of Dyre must be extended. Here we analyse the dielectric properties of a polymer blend made up with the semiconducting poly(o-methoxyaniline) and poly(vinylidene fluoride-trifluorethylene) POMA/P(VDF-TrFE), and of a hybrid composite of POMA/P(VDF-TrFE)/Zn2SiO4:Mn. For the blend, the Lepienski model, which takes into account the rotation or stretching of electric dipoles, provided excellent fitting to the ac impedance data. Because two phases had to be assumed for the hybrid composite, we had to extend the Lepienski model to fit the data, by incorporating a second transport mechanism. The two mechanisms were associated with the electronic transport in the polymeric matrix and with transport at the interfaces between Zn2SiO4:Mn microparticles and the polymeric matrix, with the relative importance of the interfacial component increasing with the percentage of Zn2SiO4:Mn in the composite. The analysis of impedance data at various temperatures led to a prediction of the theoretical model of a change in morphology at 190 ± 40 K, and this was confirmed experimentally with a differential scanning calorimetry experiment.

The phase transition from the non-polar α-phase to the polar β-phase of poly(vinylidene fluoride) (PVDF) has been investigated using micro-Raman spectroscopy, which is advantageous because it is a nondestructive technique. Films of α-PVDF were subjected to stretching under controlled rates at 80 °C, while the transition to β-PVDF was monitored by the decrease in the Raman band at 794 cm−1 characteristic of the α-phase, along with the concomitant increase in the 839 cm−1 band characteristic of the β-phase. The α→β transition in our PVDF samples could be achieved even for the sample stretched to twice (2×-stretched) the initial length and it did not depend on the stretching rate in the range between 2.0 and 7.0 mm/min. These conclusions were corroborated by differential scanning calorimetry (DSC) and X-ray diffraction experiments for PVDF samples processed under the same conditions as in the Raman scattering measurements. Poling with negative corona discharge was found to affect the α-PVDF morphology, improving the Raman bands related to this crystalline phase. This effect is minimized for films stretched to higher ratios. Significantly, corona-induced effects could not be observed with the other experimental techniques, i.e., X-ray diffraction and infrared spectroscopy.

Light-emitting electrochemical cells (LECs) made of electroluminescent polymers were studied by d.c. and transient current-voltage and luminance-voltage measurements to elucidate the operation mechanisms of this kind of device. The time and external voltage necessary to form electrical double layers (EDLs) at the electrode interfaces could be determined from the results. In the low- and intermediate-voltage ranges (below 1.1 V), the ionic transport and the electronic diffusion dominate the current, being the device operation better described by an electrodynamic model. For higher voltages, electrochemical doping occurs, giving rise to the formation of a p-i-n junction, according to an electrochemical doping model.

Made available in DSpace on 2013-08-28T14:08:41Z (GMT). No. of bitstreams: 1 WOS000309329300080.pdf: 1369965 bytes, checksum: d75c2311521815dd489163f80d7e13ba (MD5) Made available in DSpace on 2013-09-30T18:43:40Z (GMT). No. of bitstreams: 2 WOS000309329300080.pdf: 1369965 bytes, checksum: d75c2311521815dd489163f80d7e13ba (MD5) WOS000309329300080.pdf.txt: 24875 bytes, checksum: d3f96bc9ac1889d4dfef27c14947d8cc (MD5) Previous issue date: 2012-09-10 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T14:02:43Z No. of bitstreams: 2 WOS000309329300080.pdf: 1369965 bytes, checksum: d75c2311521815dd489163f80d7e13ba (MD5) WOS000309329300080.pdf.txt: 24875 bytes, checksum: d3f96bc9ac1889d4dfef27c14947d8cc (MD5) Made available in DSpace on 2014-05-20T14:02:43Z (GMT). No. of bitstreams: 2 WOS000309329300080.pdf: 1369965 bytes, checksum: d75c2311521815dd489163f80d7e13ba (MD5) WOS000309329300080.pdf.txt: 24875 bytes, checksum: d3f96bc9ac1889d4dfef27c14947d8cc (MD5) Previous issue date: 2012-09-10 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) National Institute of Organic Electronics (INEO) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Frequency-dependent electroluminescence and electric current response spectroscopy were applied to polymeric light-emitting electrochemical cells in order to obtain information about the operation mechanism regimes of such devices. Three clearly distinct frequency regimes could be identified: a dielectric regime at high frequencies; an ionic transport regime, characterized by ionic drift and electronic diffusion; and an electrolytic regime, characterized by electronic injection from the electrodes and electrochemical doping of the conjugated polymer. From the analysis of the results, it was possible to evaluate parameters like the diffusion speed of electronic charge carriers in the active layer and the voltage drop necessary for operation. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4752438] Univ São Paulo, Inst Fis Sao Carlos, BR-13560250 Sao Carlos, SP, Brazil Univ Estadual Paulista, UNESP, Dept Fis, BR-15054000 Sao Jose do Rio Preto, SP, Brazil Univ Estadual Paulista, UNESP, Dept Fis, BR-15054000 Sao Jose do Rio Preto, SP, Brazil

Neste trabalho, mostramos que uma configuração desconhecida de um circuito montado com resistores e capacitores no interior de uma "caixa preta", pode ser determinada através de uma técnica, conhecida como espectroscopia de impedância, largamente utilizada em várias areas da ciência. Como essa técnica faz uso da impedância complexa, apresentamos também uma introdução aos circuitos AC do ponto de vista do formalismo de números complexos. O arranjo experimental utiliza um gerador de audio como fonte AC para alimentar a caixa e um osciloscópio de duplo canal para medir tanto a parte real como a imaginária da impedância complexa do circuito desconhecido em função da frequência do gerador. A partir do espectro de impedância obtido, identifica-se não só a configuração do circuito no interior da caixa como também os valores das resistências e capacitâncias utilizadas para montá-lo. In this work we show that the configuration of an electrical circuit made up of resistors and capacitors in a black box may be determined using impedance spectroscopy, a technique that has been largely used in several scientific areas. Because the complex impedance is measured in this technique, we present basic concepts of a.c. electrical circuits analyzed with the formalism of complex numbers. The experimental setup includes a radiofrequency generator as the a.c. source for the circuit and a double-channel oscilloscope to measure both the real and imaginary parts of the complex impedance of the circuit in the black box. From the impedance spectrum we can not only determine the configuration of the electrical circuit in the black box but also the values of resistors and capacitors used.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2013-08-22T18:43:51Z No. of bitstreams: 1 S1806-11172008000400013.pdf: 256185 bytes, checksum: 07f813c402eb3703ec04e136e33d6d48 (MD5) Made available in DSpace on 2013-08-22T18:43:51Z (GMT). No. of bitstreams: 1 S1806-11172008000400013.pdf: 256185 bytes, checksum: 07f813c402eb3703ec04e136e33d6d48 (MD5) Previous issue date: 2008-12-01 Made available in DSpace on 2013-09-30T18:51:06Z (GMT). No. of bitstreams: 2 S1806-11172008000400013.pdf: 256185 bytes, checksum: 07f813c402eb3703ec04e136e33d6d48 (MD5) S1806-11172008000400013.pdf.txt: 33309 bytes, checksum: 1499ea1cb1d4c7b80f960c2fe5c5982e (MD5) Previous issue date: 2008-12-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T14:16:47Z No. of bitstreams: 2 S1806-11172008000400013.pdf: 256185 bytes, checksum: 07f813c402eb3703ec04e136e33d6d48 (MD5) S1806-11172008000400013.pdf.txt: 33309 bytes, checksum: 1499ea1cb1d4c7b80f960c2fe5c5982e (MD5) Made available in DSpace on 2014-05-20T14:16:47Z (GMT). No. of bitstreams: 2 S1806-11172008000400013.pdf: 256185 bytes, checksum: 07f813c402eb3703ec04e136e33d6d48 (MD5) S1806-11172008000400013.pdf.txt: 33309 bytes, checksum: 1499ea1cb1d4c7b80f960c2fe5c5982e (MD5) Previous issue date: 2008-12-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação para o Desenvolvimento da UNESP (FUNDUNESP) Neste trabalho, mostramos que uma configuração desconhecida de um circuito montado com resistores e capacitores no interior de uma caixa preta, pode ser determinada através de uma técnica, conhecida como espectroscopia de impedância, largamente utilizada em várias areas da ciência. Como essa técnica faz uso da impedância complexa, apresentamos também uma introdução aos circuitos AC do ponto de vista do formalismo de números complexos. O arranjo experimental utiliza um gerador de audio como fonte AC para alimentar a caixa e um osciloscópio de duplo canal para medir tanto a parte real como a imaginária da impedância complexa do circuito desconhecido em função da frequência do gerador. A partir do espectro de impedância obtido, identifica-se não só a configuração do circuito no interior da caixa como também os valores das resistências e capacitâncias utilizadas para montá-lo. In this work we show that the configuration of an electrical circuit made up of resistors and capacitors in a black box may be determined using impedance spectroscopy, a technique that has been largely used in several scientific areas. Because the complex impedance is measured in this technique, we present basic concepts of a.c. electrical circuits analyzed with the formalism of complex numbers. The experimental setup includes a radiofrequency generator as the a.c. source for the circuit and a double-channel oscilloscope to measure both the real and imaginary parts of the complex impedance of the circuit in the black box. From the impedance spectrum we can not only determine the configuration of the electrical circuit in the black box but also the values of resistors and capacitors used. Universidade Estadual Paulista Júlio de Mesquita Filho Instituto de Geociências e Ciências Exatas Departamento de Física Universidade Estadual Paulista Júlio de Mesquita Filho Instituto de Geociências e Ciências Exatas Departamento de Física

As células solares orgânicas, ou dispositivos fotovoltaicos orgânicos (OPVs), vêm se consolidando como uma tecnologia promissora para a geração de energia limpa e renovável devido aos progressos observados nos últimos anos em termos de eficiência e, sobretudo, ao seu baixo custo e facilidade de processamento, e à sua adaptabilidade à eletrônica flexível. Entretanto, ainda se faz necessário aumentar sua eficiência, sua estabilidade e seu tempo de vida de operação. Esses desafios só serão superados por meio de uma melhor compreensão dos processos de geração e de recombinação dos portadores fotogerados, e dos fenômenos de transporte eletrônico ao longo do dispositivo, desde a geração dos portadores até sua coleta pelos eletrodos. A perda de propriedades quando em operação sob condições ambientais é outro obstáculo a ser vencido, e para isso, é necessário conhecer as razões que provocam a degradação do dispositivo. Neste contexto, esta tese tem por objetivo o estudo de propriedades fundamentais que governam a geração, recombinação, transporte e coleta de cargas pelos eletrodos de células solares orgânicas com estrutura ITO/PEDOT:PSS/PTB7-Th:PC71BM/Ca/Al em diferentes condições de funcionamento. Em específico, em atmosfera inerte de nitrogênio e em atmosfera ambiente. O primeiro passo nesse sentido foi a fabricação e otimização dos dispositivos através de diferentes métodos experimentais. Conseguimos progredir muito na parte de confecção, produzindo células OPVs com eficiência de 7,85 %. Posteriormente, realizamos um estudo comparativo entre dois dispositivos com essa estrutura, sendo a diferença entre eles a adição de um aditivo durante a preparação da camada ativa (PTB7-Th:PC71BM): a molécula de 1,8-diiodooctano (DIO). Os dispositivos foram então caracterizados por técnicas de absorção de UVVis e Microscopia de Força Atômica (AFM). Os estudos elétricos dos dispositivos foram realizados por medidas de J-V no escuro e sob iluminação (1 sol), em diferentes temperaturas (150 a 300 K). Com o auxílio da equação de Mott-Gurney obtivemos os valores de mobilidade eletrônica (μ) dos portadores de cargas, para diferentes temperaturas, em ajustando-se as curvas de retificação no escuro. Os ajustes das respostas J-V (fotocorrente) sob iluminação foram ajustadas por uma equação derivada da cinética das taxas de geração e extração, em considerando-se cinética de segunda ordem para a recombinação bimolecular, de onde extraímos a razão μ2k (k é o coeficiente de recombinação) também para diferentes temperaturas. Deste estudo, foi possível concluir que o efeito do DIO na morfologia da camada ativa melhora o processo de condução por hopping e diminui o coeficiente de recombinação, o que possibilita um melhor desempenho fotovoltaico do dispositivo. Esse estudo permitiu obter o fator de redução (ζ) do coeficiente de recombinação, e sua variação com a temperatura. O nosso último estudo foi investigar os mecanismos de degradação de um dispositivo com DIO exposto em condições ambientais, sobretudo devido à ação do oxigênio. Nesse estudo foram realizadas medidas de Foto-CELIV (Extração da Corrente pelo Aumento Linear da Tensão -CELIV) e os ajustes das curvas de J-V sob iluminação foram feitos pela equação de circuito equivalente de uma célula solar dos quais obteve-se a variação das resistências série e paralelo em função do tempo de exposição ao ambiente. Organic solar cells, or organic photovoltaics devices (OPVs), have been consolidating as a promising technology for the generation of clean and renewable energy due to the progress observed in recent years in terms of efficiency, and above all by its low cost and ease of processing, and their adaptability to flexible electronics. However, it is still required to increase its efficiency, its stability and its operating life. These challenges will only be overcome through a better understanding of the processes of generation and recombination of the photogenerated carriers, and of the phenomena of electronic transport throughout the device, from the generation of the carriers to their collection by the electrodes. The loss of properties when operating under environmental conditions is another obstacle to be overcome, and for this, is mandatory to well known the reasons of degradation effects. In this context, this thesis aims at the study of fundamental properties that govern the generation, recombination, transport and collection of charges by the electrodes, at different operating conditions, having ITO/PEDOT:PSS/PTB7-Th:PC71BM/Ca/Al as structure. Specifically, in an inert atmosphere of nitrogen, and in an ambient atmosphere. The first step in this direction was the manufacturing and optimization of the devices through different experimental methods. We achieved a great of progress in the manufacturing process, producing OPV cells with 7.85% efficiency. Afterward, we performed a comparative study between two devices of this structure, the difference between them being the addition of an additive during the preparation of the active layer (PTB7-Th: PC71BM): the 1,8-diiodooctane (DIO) molecule. The devices were then characterized by UV-Vis absorption techniques and Atomic Force Microscopy (AFM).The electrical studies of the devices were performed by J-V measurements, in the dark and under illumination (1 sol), at different temperatures (150 to 300 K). With the aid of the Mott-Gurney equation we obtained the values of electronic mobility (μ) of the charge carriers, for different temperatures, by adjusting the rectification curves in the dark. The adjustments of the JV responses under illumination were obtained by an equation that was derived from the kinetics of the generation and extraction rates, considering second-order kinetics for bimolecular recombination. From such fitting, it was extracted the μ2k ratio (k is the coefficient of recombination) also for different temperatures. From this study, it was possible to conclude that the effect of DIO on the active layer morphology improves the hopping conduction and decreases the recombination coefficient, leading to a better photovoltaic performance of the device. This study allowed to obtain the reduction factor (ζ) of the recombination coefficient, and its variation with temperature. Our last study was to investigate the mechanisms of degradation of a device with DIO exposed in environmental conditions, mainly due to the action of oxygen. In this study, photo-CELIV (Current Extraction by Linear Increasing Voltage - CELIV).technique was performed and the adjustments of the J-V curves under illumination were made by the equivalent circuit equation of a solar cell, from which the variation of the series and parallel resistances was obtained as a function of the exposure time to the environment.