Showing papers on "Solar cell published in 2007"
TL;DR: These coaxial silicon nanowire photovoltaic elements provide a new nanoscale test bed for studies of photoinduced energy/charge transport and artificial photosynthesis, and might find general usage as elements for powering ultralow-power electronics and diverse nanosystems.
Abstract: Solar cells are attractive candidates for clean and renewable power; with miniaturization, they might also serve as integrated power sources for nanoelectronic systems. The use of nanostructures or nanostructured materials represents a general approach to reduce both cost and size and to improve efficiency in photovoltaics. Nanoparticles, nanorods and nanowires have been used to improve charge collection efficiency in polymer-blend and dye-sensitized solar cells, to demonstrate carrier multiplication, and to enable low-temperature processing of photovoltaic devices. Moreover, recent theoretical studies have indicated that coaxial nanowire structures could improve carrier collection and overall efficiency with respect to single-crystal bulk semiconductors of the same materials. However, solar cells based on hybrid nanoarchitectures suffer from relatively low efficiencies and poor stabilities. In addition, previous studies have not yet addressed their use as photovoltaic power elements in nanoelectronics. Here we report the realization of p-type/intrinsic/n-type (p-i-n) coaxial silicon nanowire solar cells. Under one solar equivalent (1-sun) illumination, the p-i-n silicon nanowire elements yield a maximum power output of up to 200 pW per nanowire device and an apparent energy conversion efficiency of up to 3.4 per cent, with stable and improved efficiencies achievable at high-flux illuminations. Furthermore, we show that individual and interconnected silicon nanowire photovoltaic elements can serve as robust power sources to drive functional nanoelectronic sensors and logic gates. These coaxial silicon nanowire photovoltaic elements provide a new nanoscale test bed for studies of photoinduced energy/charge transport and artificial photosynthesis, and might find general usage as elements for powering ultralow-power electronics and diverse nanosystems.
2,879 citations
TL;DR: In this article, an efficiency of 40.7% was achieved for a metamorphic three-junction GaInP∕GaInAs∕Ge cell under the standard spectrum for terrestrial concentrator solar cells at 240 suns (24.0W∕cm2, AM1.5D, low aerosol optical depth, 25°C).
Abstract: An efficiency of 40.7% was measured and independently confirmed for a metamorphic three-junction GaInP∕GaInAs∕Ge cell under the standard spectrum for terrestrial concentrator solar cells at 240 suns (24.0W∕cm2, AM1.5D, low aerosol optical depth, 25°C). This is the initial demonstration of a solar cell with over 40% efficiency, and is the highest solar conversion efficiency yet achieved for any type of photovoltaic device. Lattice-matched concentrator cells have now reached 40.1% efficiency. Electron-hole recombination mechanisms are analyzed in metamorphic GaxIn1−xAs and GaxIn1−xP materials, and fundamental power losses are quantified to identify paths to still higher efficiencies.
1,205 citations
TL;DR: In this paper, the self-organization of the polymer in solar cells based on regioregular poly(3-hexylthiophene) (RR-P3HT):[6,6]-phenyl C61-butyric acid methyl ester (PCBM) is studied systematically as a function of the spin-coating time.
Abstract: The self-organization of the polymer in solar cells based on regioregular poly(3-hexylthiophene) (RR-P3HT):[6,6]-phenyl C61-butyric acid methyl ester (PCBM) is studied systematically as a function of the spin-coating time ts (varied from 20–80 s), which controls the solvent annealing time ta, the time taken by the solvent to dry after the spin-coating process. These blend films are characterized by photoluminescence spectroscopy, UV-vis absorption spectroscopy, atomic force microscopy, and grazing incidence X-ray diffraction (GIXRD) measurements. The results indicate that the π-conjugated structure of RR-P3HT in the films is optimally developed when ta is greater than 1 min (ts ∼ 50 s). For ts < 50 s, both the short-circuit current (JSC) and the power conversion efficiency (PCE) of the corresponding polymer solar cells show a plateau region, whereas for 50 < ts < 55 s, the JSC and PCE values are significantly decreased, suggesting that there is a major change in the ordering of the polymer in this time window. The PCE decreases from 3.6 % for a film with a highly ordered π-conjugated structure of RR-P3HT to 1.2 % for a less-ordered film. GIXRD results confirm the change in the ordering of the polymer. In particular, the incident photon-to-electron conversion efficiency spectrum of the less-ordered solar cell shows a clear loss in both the overall magnitude and the long-wavelength response. The solvent annealing effect is also studied for devices with different concentrations of PCBM (PCBM concentrations ranging from 25 to 67 wt %). Under “solvent annealing” conditions, the polymer is seen to be ordered even at 67 wt % PCBM loading. The open-circuit voltage (VOC) is also affected by the ordering of the polymer and the PCBM loading in the active layer.
1,165 citations
TL;DR: An electron-transport polymer with good solution processibility, excellent thermal stability, and high electron affinity based on alternating perylene diimide and dithienothiophene units has been synthesized.
Abstract: An electron-transport polymer with good solution processibility, excellent thermal stability, and high electron affinity based on alternating perylene diimide and dithienothiophene units has been synthesized Electron mobilities as high as 13 × 10-2 cm2 V-1 s-1 have been measured in field-effect transistor geometry The polymer shows broad absorptions throughout the visible and extending into the near-IR A power conversion efficiency of over 1%, under simulated AM 15, 100 mW/cm2, was measured for a single-layer solar cell using this polymer as an acceptor and a polythiophene derivative as a donor
1,091 citations
TL;DR: CdSe semiconductor nanocrystals and single-crystal ZnO nanowires are combined to demonstrate a new type of quantum-dot-sensitized nanowire solar cell that exhibited short-circuit currents ranging from 1 to 2 mA/cm2 and open-circuits voltages of 0.5-0.6 V when illuminated with 100 mW/ cm2 simulated AM1.5 spectrum.
Abstract: We combine CdSe semiconductor nanocrystals (or quantum dots) and single-crystal ZnO nanowires to demonstrate a new type of quantum-dot-sensitized solar cell. An array of ZnO nanowires was grown vertically from a fluorine-doped tin oxide conducting substrate. CdSe quantum dots, capped with mercaptopropionic acid, were attached to the surface of the nanowires. When illuminated with visible light, the excited CdSe quantum dots injected electrons across the quantum dot−nanowire interface. The morphology of the nanowires then provided the photoinjected electrons with a direct electrical pathway to the photoanode. With a liquid electrolyte as the hole transport medium, quantum-dot-sensitized nanowire solar cells exhibited short-circuit currents ranging from 1 to 2 mA/cm2 and open-circuit voltages of 0.5−0.6 V when illuminated with 100 mW/cm2 simulated AM1.5 spectrum. Internal quantum efficiencies as high as 50−60% were also obtained.
957 citations
TL;DR: In this article, the spectral and angular dependences of the electroluminescence of solar cells and light emitting diodes were analyzed and a rigorous proof for a reciprocity theorem was given.
Abstract: A rigorous proof for a reciprocity theorem that relates the spectral and angular dependences of the electroluminescence of solar cells and light emitting diodes to the spectral and angular quantum efficiency of photocarrier collection is given. An additional relation is derived that connects the open circuit voltage of a solar cell and its electroluminescence quantum efficiency.
941 citations
TL;DR: Here, a photonic crystal-based light-trapping approach is analyzed and compared to previous approaches for c-Si thin film solar cells, which gives rise to weak absorption of one-third of usable solar photons.
Abstract: Most photovoltaic (solar) cells are made from crystalline silicon (c-Si), which has an indirect band gap. This gives rise to weak absorption of one-third of usable solar photons. Therefore, improved light trapping schemes are needed, particularly for c-Si thin film solar cells. Here, a photonic crystal-based light-trapping approach is analyzed and compared to previous approaches. For a solar cell made of a 2 µm thin film of c-Si and a 6 bilayer distributed Bragg reflector (DBR) in the back, power generation can be enhanced by a relative amount of 24.0% by adding a 1D grating, 26.3% by replacing the DBR with a six-period triangular photonic crystal made of air holes in silicon, 31.3% by a DBR plus 2D grating, and 26.5% by replacing it with an eight-period inverse opal photonic crystal.
715 citations
TL;DR: In this article, the synthesis, electronic, and photovoltaic properties of green porphyrin sensitizers were reported, and the best performing dye under standard global AM 1.5 solar conditions gives a short circuit photocurrent density (jsc) of 14.0 ± 0.20 mA/cm2, an open circuit voltage of 680 ± 30 mV, and a fill factor of 0.74, corresponding to an overall conversion efficiency of 7.1%.
Abstract: In TiO2-based dye-sensitized nanocrystalline solar cells, efficiencies of up to 11% have been obtained using Ru dyes, but the limited availability of these dyes together with their undesirable environmental impact have led to the search for cheaper and safer organic-based dyes. In this Letter, we report the synthesis, electronic, and photovoltaic properties of novel green porphyrin sensitizers. All six porphyrin dyes give solar cell efficiencies of ≥5%, but the best performing dye under standard global AM 1.5 solar conditions gives a short circuit photocurrent density (jsc) of 14.0 ± 0.20 mA/cm2, an open circuit voltage of 680 ± 30 mV, and a fill factor of 0.74, corresponding to an overall conversion efficiency of 7.1%, which, for porphyrin-based sensitizers, is unprecedented. This same dye gives an efficiency of 3.6% in a solid-state cell with spiro-MeOTAD as the hole transporting component, comparable to solid-state cells incorporating the best performing ruthenium dyes.
715 citations
TL;DR: In this article, three ways in which the cell efficiency of silicon solar cells may be improved by better exploitation of the solar spectrum: down-conversion (cutting one high energy photon into two low energy photons), photoluminescence (shifting photons into wavelength regions better accepted by the solar cell), and up-converting (combining low-energy photons to one high-energy photon).
585 citations
TL;DR: In this article, an overview of dye-sensitized solar cells (DSC) with enhanced efficiencies and stabilities is presented, and an outlook summarizing future directions in the research and large-scale production of DSC is presented.
Abstract: This paper presents an overview of the research carried out by a European consortium with the aim to develop and test new and improved ways to realise dye-sensitized solar cells (DSC) with enhanced efficiencies and stabilities. Several new areas have been explored in the field of new concepts and materials, fabrication protocols for TiO2 and scatterlayers, metal oxide blocking layers, strategies for co-sensitization and low temperature processes of platinum deposition. Fundamental understanding of the working principles has been gained by means of electrical and optical modelling and advanced characterization techniques. Cost analyses have been made to demonstrate the potential of DSC as a low cost thin film PV technology. The combined efforts have led to maximum non-certified power conversion efficiencies under full sunlight of 11% for areas <02 cm2 and 101% for a cell with an active area of 13 cm2. Lifetime studies revealed negligible device degradation after 1000 hrs of accelerated tests under thermal stress at 80°C in the dark and visible light soaking at 60°C. An outlook summarizing future directions in the research and large-scale production of DSC is presented.
566 citations
TL;DR: In this paper, zinc oxide (ZnO) has been explored as an alternative material in dye-sensitized solar cells with great potential, and the main reasons for this increase in research surrounding ZnO material include: 1) zinc oxide having a band gap similar to that for TiO2 at 3.2 eV, and 2) Znoxide having a much higher electron mobility ~ 115-155 cm2/Vs.
Abstract: The interest in dye-sensitized solar cells has increased due to reduced energy sources and higher energy production costs. For the most part, titania (TiO2) has been the material of choice for dye-sensitized solar cells and so far have shown to exhibit the highest overall light conversion efficiency ~ 11%.[1] However, zinc oxide (ZnO) has recently been explored as an alternative material in dye-sensitized solar cells with great potential.[2] The main reasons for this increase in research surrounding ZnO material include: 1) ZnO having a band gap similar to that for TiO2 at 3.2 eV,[3] and 2) ZnO having a much higher electron mobility ~ 115-155 cm2/Vs[4] than that for anatase titania (TiO2), which is reported to be ~ 10-5 cm2/Vs.[5] In addition, ZnO has a few advantages as the semiconductor electrode when compared to TiO2, including 1) simpler tailoring of the nanostructure as compared to TiO2, and 2) easier modification of the surface structure. These advantages[6] are thought to provide a promising means for improving the solar cell performance of the working electrode in dye-sensitized solar cells.
TL;DR: In this paper, a modeling process configuring a computer simulation model, able to demonstrate the cell's output features in terms of irradiance and temperature environment changes, is investigated, based on four parameters, and it is tested to simulate three popular types of photovoltaic panels constructed with different materials: copper indium diselenide (CIS) thin film, multi-crystalline silicon, and mono-celline silicon.
TL;DR: In this article, a dye-sensitized solar cell (DSSC) using a ZnO-nanoflower film photoanode, which was grown by a hydrothermal method at 95°C.
Abstract: In this letter, the authors report a dye-sensitized solar cell (DSSC) using a ZnO-nanoflower film photoanode, which was grown by a hydrothermal method at 95°C. The dye used was cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)-ruthenium(II) bis-tetrabutylam-monium (N-719). At AM1.5G irradiation with 100mW∕cm2 light intensity, the DSSC based on ZnO-nanoflower film showed an energy conversion efficiency of 1.9%, which is much higher compared to that (1.0%) of the control device constructed using a photoanode of upstanding ZnO-nanorod array fabricated by hydrothermal method as well. The better performance of ZnO-nanoflower DSSC was due to a better dye loading and light harvesting of the ZnO-nanoflower film. The results demonstrate potential application of ZnO-nanoflower array for efficient dye-sensitized solar cells.
TL;DR: In this article, a large area (>10 cm 2 ) interconnected organic solar cell modules are reported, both on glass substrates as well as on flexible ultra-high barrier foils, reaching 1.5% and 0.5 % overall power conversion efficiency under AM1.5 conditions.
TL;DR: The recent boom in the demand for photovoltaic modules has created a silicon supply shortage, providing an opportunity for thin-films to enter the market in significant quantities.
Abstract: The recent boom in the demand for photovoltaic modules has created a silicon supply shortage, providing an opportunity for thin-film photovoltaic modules to enter the market in significant quantities. Thin-films have the potential to revolutionise the present cost structure of photovoltaics by eliminating the use of the expensive silicon wafers that alone account for above 50% of total module manufacturing cost. The strengths and weaknesses of the contending thin-film photovoltaic technologies and the current state of commercial activity with each are briefly reviewed.
TL;DR: In this article, an ordered organic−inorganic solar cell architecture based on ZnO−TiO2 core−shell nanorod arrays encased in the hole-conducting polymer P3HT was evaluated.
Abstract: We evaluate an ordered organic−inorganic solar cell architecture based on ZnO−TiO2 core−shell nanorod arrays encased in the hole-conducting polymer P3HT. Thin shells of TiO2 grown on the ZnO nanorods by atomic layer deposition significantly increase the voltage and fill factor relative to devices without shells. We find that the core−shell cells must be exposed to air to reproducibly attain efficiencies higher than 0.05%. Cells stored in air for 1 month are 0.29% efficient.
TL;DR: A highly efficient organic dye is synthesized for a dye-sensitized solar cell and the overall solar-to-energy conversion efficiency was 9.1% at AM 1.5 illumination.
TL;DR: In this paper, a Ge-free III-V semiconductor triple-junction solar cell was presented, which achieved 33.8, 30.6, and 38.9% efficiencies under the standard 1sun global spectrum, space spectrum, and concentrated direct spectrum at 81suns, respectively.
Abstract: The authors demonstrate a thin, Ge-free III–V semiconductor triple-junction solar cell device structure that achieved 33.8%, 30.6%, and 38.9% efficiencies under the standard 1sun global spectrum, space spectrum, and concentrated direct spectrum at 81suns, respectively. The device consists of 1.8eV Ga0.5In0.5P, 1.4eV GaAs, and 1.0eV In0.3Ga0.7As p-n junctions grown monolithically in an inverted configuration on GaAs substrates by organometallic vapor phase epitaxy. The lattice-mismatched In0.3Ga0.7As junction was grown last on a graded GaxIn1−xP buffer. The substrate was removed after the structure was mounted to a structural “handle.” The current-matched, series-connected junctions produced a total open-circuit voltage over 2.95V at 1sun.
TL;DR: In this article, instead of water, alcohol was used as a solvent in a chemical bath deposition process for the in situ synthesis of CdS quantum dots onto mesoporous TiO2 films.
Abstract: Alcohol, instead of water, was used as a solvent in a chemical bath deposition process for the in situ synthesis of CdS quantum dots onto mesoporous TiO2 films. Due to low surface tension, the alcohol solutions have high wettability and superior penetration ability on the mesoscopic TiO2 film, leading to a well-covered CdS on the surface of mesopores. The CdS-sensitized TiO2 electrode prepared using the alcohol system not only has a higher incorporated amount of CdS but also greatly inhibits the recombination of injected electrons. The efficiency of a CdS quantum-dots-sensitized solar cell prepared using the present method is as high as 1.84% under the illumination of one sun (AM1.5, 100mW∕cm2).
TL;DR: In this paper, the authors investigated synthesis conditions and some properties of sprayed Cu 2 ZnSnS 4 (CZTS) thin films in order to determine the best preparation conditions for the realization of CZTS based photovoltaic solar cells.
TL;DR: In this paper, the effects of non-uniform solar irradiation distribution on energy output of different interconnected configurations in photovoltaic (PV) arrays are investigated, and a PV module model is developed to find which configuration is less susceptible to mismatch effects.
TL;DR: The basic physical and chemical principles behind the dye-sensitized nanocrystalline solar cell (DSC: also known as the Grätzel cell after its inventor) are outlined in order to clarify the differences and similarities between the DSC and conventional semiconductor solar cells.
Abstract: The basic physical and chemical principles behind the dye-sensitized nanocrystalline solar cell (DSC: also known as the Gratzel cell after its inventor) are outlined in order to clarify the differences and similarities between the DSC and conventional semiconductor solar cells. The roles of the components of the DSC (wide bandgap oxide, sensitizer dye, redox electrolyte or hole conductor, counter electrode) are examined in order to show how they influence the performance of the system. The routes that can lead to loss of DSC performance are analyzed within a quantitative framework that considers electron transport and interfacial electron transfer processes, and strategies to improve cell performance are discussed. Electron transport and trapping in the mesoporous oxide are discussed, and a novel method to probe the electrochemical potential (quasi Fermi level) of electrons in the DSC is described. The article concludes with an assessment of the prospects for future development of the DSC concept.
TL;DR: Polycrystalline n-ZnO/p-Cu2O heterojunctions have been fabricated by low-temperature eletrodepositions of ZnO and Cu2O layers in aqueous solutions as mentioned in this paper.
Abstract: Polycrystalline n-ZnO/p-Cu2O heterojunctions have been fabricated by low-temperature eletrodepositions of ZnO and Cu2O layers in aqueous solutions. The condition for forming the Cu2O layer significantly reflected the electrical rectification characteristic and the photovoltaic performance, and the heterojunction fabricated under optimized conditions showed an excellent electrical rectification characteristic and a photovoltaic performance of 1.28% in conversion efficiency under an AM 1.5 illumination.
TL;DR: In this paper, a modified 3-diode equivalent circuit model for analysis of multicrystalline silicon (Mc-Si) solar cells was proposed to precisely evaluate the characteristics of Mc-Si solar cells taking the influence of grain boundaries and large leakage current through the peripheries into consideration and extract electrical properties.
TL;DR: In this article, the insertion of a TiOx layer between the Al electrode and the active layer of an organic photovoltaic cell resulted in a high performance with 94% durability under irradiation (100mW∕cm2) for 100h and had improved fill factor and open circuit voltage.
Abstract: Insertion of a TiOx layer between the Al electrode and the active layer of an organic photovoltaic cell resulted in a high performance with 94% durability under irradiation (100mW∕cm2) for 100h and had improved fill factor and open circuit voltage. An efficiency of 4.05% was achieved by using the cell containing a TiOx layer fabricated and measured in ambient atmosphere. The TiOx layer works as an effective barrier to physical damage and chemical degradation, resulting in high durability under aerobic conditions, and also serves as a hole blocking layer, resulting in improved parallel resistance and rectification.
TL;DR: In this article, the authors used screen-printing of an active layer onto an indium-tinoxide (ITO) electrode pattern on a 200-μm polyethyleneterphthalate (PET) substrate.
Abstract: Preliminary data on the fabrication of 0.1 m 2 polymer solar cells are presented. The process employed screen-printing of an active layer onto an indium-tin-oxide (ITO) electrode pattern (50 Ω square −1 ) on a 200 μm polyethyleneterphthalate (PET) substrate. After the printing, vacuum coating of an optional layer of C 60 and the final aluminium electrode was employed to complete the device. The active layer consisted of poly-1,4-(2-methoxy-5-ethylhexyloxy)phenylenevinylene (MEH-PPV). Chlorobenzene was used as solvent for the screen-printing process. The design of the solar cell module was chosen to employ both serial and parallel connection of individual solar cells. Thirteen individual solar cells with an active area of 7.2 cm 2 were thus connected in series. The serial connection was chosen to reduce the current density for the large area employed. A step up in voltage is thus preferable to avoid resistive loss. The parallel connection of seven such rows through a screen-printed silver bus gave a solar cell module measuring 40 cm × 25 cm (0.1 m 2 ). The active area was 65% of the total area. The remaining 35% of the area was used for interconnections between cells and for the separation between rows. The 65% active area was chosen to encompass a good margin for prototyping/research and to keep contact resistances between the cells low. In a fully automated process the active area could perhaps reach 90–99% interval but problems with current extraction and interconnections were found to become very critical. There are obvious shortcomings to this approach but the advantage of low current density is believed to be the biggest problem in efficient energy extraction from the module when no simple method for reducing the sheet resistance is available. In the simple geometry ITO/MEH-PPV/aluminium the module gave an open circuit voltage ( V oc ) of 10.5 V, a short circuit current ( I sc ) of 5 μA, a fill factor (FF) of 13% and an efficiency ( η ) of 0.00001% under AM1.5 illumination with an incident light intensity of 1000 W m −2 . A geometry employing a sublimed layer of C 60 (ITO/MEH-PPV/C 60 /Al) improved V oc , I sc , FF and η to 3.6 V, 178 μA, 19% and 0.0002%, respectively. The lifetimes ( τ ½ ) of the devices defined as the time it takes for the module efficiency to attain half of its maximum value were found to improve significantly when a sublimed layer of C 60 was included between the polymer and the aluminium electrode. The modules were laminated with 200 μm polyethyleneterephthalate (PET) foil to mechanically protect the cells. τ ½ values of 150 h were typically obtained. This short lifetime is linked to reaction between the reactive metal electrode (aluminium) and the constituents of the active layer. The modules were tested outdoors in different weather condition (wind, high temperature excursion, rain, snow). Tested during a storm the polymer photovoltaic laminate was subject to vibration stress and deformation and delamination in the organic layer was observed with fast bleaching of the active material. Efficient encapsulation with barriers that has very low oxygen and water permeabilities will be needed before future commercialisation can be anticipated.
TL;DR: A squaraine dye incorporating two carboxylic acid attaching groups has been synthesised and used successfully in both liquid and solid-state solar cells, with solar energy to electricity conversion efficiencies under AM 1.5 G irradiation.
TL;DR: In this article, the series resistance of a monocrystalline industrial screen printed silicon solar cell was measured using luminescence images taken by a thermoelectrically cooled silicon charge coupled device camera.
Abstract: The fast determination of the spatially resolved series resistance of silicon solar cells from luminescence images is demonstrated. Strong lateral variation of the series resistance determined from luminescence images taken on an industrial screen printed silicon solar cell is confirmed qualitatively by a Corescan measurement and quantitatively by comparison with the total series resistance obtained from the terminal characteristics of the cell. Compared to existing techniques that measure the spatially resolved series resistance, luminescence imaging has the advantage that it is nondestructive and orders of magnitude faster. © 2007 American Institute of Physics. DOI: 10.1063/1.2709630 The series resistance of silicon solar cells often exhibits strong lateral variations, particularly in industrial screen printed cells. Experimental techniques to quantify such variations include Corescan, 1 Cello, 2 and imaging techniques based on dark and illuminated infrared lock-in thermography LIT. 3,4 These techniques require data acquisition times between minutes and several hours per solar cell. Electroluminescence EL and photoluminescence PL imaging are very fast characterization tools for silicon solar cells and silicon wafers, with data acquisition times of a few seconds or less per sample. 5,6 Using EL images and PL images taken with external control of the voltage to measure lateral variations of the series resistance in silicon solar cells was proposed in Ref. 7. Some preliminary qualitative results were also reported. 7,8 Here, we demonstrate a quantitative determination of the series resistance and its lateral variation in a monocrystalline industrial screen printed silicon solar cell by luminescence imaging. Photoluminescence images are taken using an 815 nm/25 W laser that is expanded to illuminate the cell area of 12.512.5 cm 2 homogeneously with up to 0.67 Sun equivalent illumination intensity. A thermoelectrically cooled silicon charge coupled device camera is used to capture luminescence images. For the PL images with simultaneous current extraction, two arrays of ten spring loaded contact pins are used to contact the busbars of the cell homogeneously. A commercially available instrument is used for Corescan measurements; illuminated IV curves are measured with a calibrated industrial cell tester. In a simplified case, a solar cell is described as a twodimensional network of parallel nodes, with each node consisting of a series connection of a local resistor Rs,i and a diode. The value of R s,i is given as
TL;DR: In this paper, a spin-coating technique was used to depose the carbon nanotubes and the results were characterized by absorption and fluorescence spectroscopy and by atomic force microscopy to underline the structure and charge transfer between the CNTs and poly(3-hexylthiophene) (P3HT).
Abstract: This Full Paper focuses on the preparation of single-walled or multi-walled carbon nanotube solutions with regioregular poly(3-hexylthiophene) (P3HT) and a fullerene derivative 1-(3-methoxycarbonyl) propyl-1 -phenyl[6,6]C 61 (PCBM) using a high dissolution and concentration method to exactly control the ratio of carbon nanotubes (CNTs) to the P3HT/PCBM mixture and disperse the CNTs homogeneously throughout the matrix. The CNT/P3HT/PCBM composites are deposed using a spin-coating technique and characterized by absorption and fluorescence spectroscopy and by atomic force microscopy to underline the structure and the charge transfer between the CNTs and P3HT. The performance of photovoltaic devices obtained using these composites as a photoactive layer mainly show an increase of the short circuit current and a slight decrease of the open circuit voltage which generally leads to an improvement of the solar cell performances to an optimum CNT percentage. The best results are obtained with a P3HT/PCBM (1:1) mixture with 0.1 wt % multi-walled carbon nanotubes with an open circuit voltage (V oc ) of 0.57 V, a current density at the short-circuit (I sc ) of 9.3 mA cm -2 and a fill factor of 38.4 %, which leads to a power conversion efficiency of 2.0 % (irradiance of 100 mW cm -2 spectroscopically distributed following AM1.5).
TL;DR: In this paper, an organic solar cell based on an active layer of an alternating copolymer, containing a fluorene and a benzothiadiazole unit with two neighboring thiophene rings, and a fullerene derivative, was measured for power conversion efficiency of 4.2% (AM1.5, 1000W∕m2).
Abstract: A power conversion efficiency of 4.2% (AM1.5, 1000W∕m2) is measured for an organic solar cell based on an active layer of an alternating copolymer, containing a fluorene and a benzothiadiazole unit with two neighboring thiophene rings, and a fullerene derivative. Using optical modeling, the absorption profile in the active layer of the solar cell is calculated and used to calculate the maximum short circuit current. The calculated currents are compared with measured currents from current-voltage measurements for various film thicknesses. From this the internal quantum efficiency is estimated to be 75% at the maximum for the best device.