Solar Cell Short Circuit Research Articles

Simulation of Bifacial and Monofacial Silicon Solar Cell Short-Circuit Current Density Under Measured Spectro-Angular Solar Irradiance

In this article, we simulated the performance of bifacial and monofacial silicon heterojunction solar cells under measured spectro-angular solar irradiance. We developed a new set-up and procedure to measure spectro-angular irradiance over a wide range of orientations. Measurements were executed in Enschede, the Netherlands ( ${52^\circ }{23^{\rm{'}}} $ N, ${\rm{ }}{6^\circ }{85^{\rm{'}}} $ E). Using this measured multi-dimensional input irradiance along with SunSolve simulated external quantum efficiency for various cells, we determined the short-circuit current density of bifacial and monofacial silicon heterojunction solar cells. We conclude that monofacial cells perform marginally better than bifacial cells for front-side illumination (up to 3.0% more for direct sun) and bifacial cells perform significantly better than monofacial cells (higher output ranging from 20.1% to 68.1%), under diffuse irradiance. We compared our results with a well-monitored roof-top solar module set-up and found good agreement for clear sky days (accuracy 1.1%–8.5%).

Metal nano-composite assisted photons harvesting in thin film organic photovoltaic

Nickel oxide (NiO) nano-particles assisted photons harvesting is studied using P3HT:PCBM blend based bulk heterojunction thin film organic solar cell (TFOSC). A comparison between devices that were fabricated at different concentration of NiO and that of the pristine P3HT:PCBM active layer were drawn up. The experimental results suggest that the incorporation of NiO in the solar absorber medium was found to be favourable for solar energy harvesting. At optimum concentration of NiO, in P3HT:PCBM blend active layer, the power conversion efficiency has grown by over 140% compared to the pristine type of devices. Moreover, significant improvement were also recorded on the solar cell fill factor (FF) and short circuit current density (JSC), respectively. The newly fabricated solar cells are discussed in terms of the optical and electrical properties of the solar absorber film.

Enhanced metal assisted etching method for high aspect ratio microstructures: Applications in silicon micropillar array solar cells

A solar cell device, fabricated on high density array cylindrical pillars, enables photogenerated carrier collection in the radial direction, thus shortening the path length of the carriers reaching the junction. It also provides advantages over conventional planar junction solar cells, such as reduced surface reflectance and enhanced light trapping. In this study, highly ordered Si micropillars were fabricated by photolithography and metal assisted etching (MAE) methods. It is shown that the use of ethanol as a solvent during the etching process and increasing HF concentration in the MAE solution both improve the quality of the surfaces of the pillars. Micropillars with smooth sidewalls and a high aspect ratio were obtained in this way. Solar cells with a radial junction were then fabricated on these micropillars. Standard doping, SiO2/SiNx passivation, and metallisation steps were carried out for the fabrication of solar cells with different micropillar lengths. A significant decrease in reflectance values was observed as the micropillar length increased, as expected. Solar cell short circuit current density (Jsc) and efficiency (η) of the solar cells tended to increase with micropillar length up to 11.5 µm and then decrease due to increased surface recombination. The maximum efficiency achieved in this study is 17.26%.

Modeling of photoactive area spreading in unstructured photovoltaic cells

In this work the influence of unstructured charge-extraction/transport layers on solar cell photocurrent measurements is investigated. Photovoltaic cells incorporating unstructured conductive layers exhibit a significant amount of photoactive area spreading. This can lead to a large error in determining solar cell short circuit current density and fill factor from I-V measurements. To counteract this effect an analytical model is developed to describe the photoactive area spreading. The developed model requires only solar cell contact geometry and transport layer sheet resistance in order to calculate the spreading current from measured I-V data. Thus total removal of unwanted spreading current from experimental data and calculation of realistic solar cell efficiency is achieved. As an example this model is applied to unstructured metal mesh based organic solar cells, and presented data show that it yields more accurate results compared to the conventional shadow masking approach.

Effects of thermally reduced graphene oxide in the photoanode on the properties of dye sensitized solar cells

This paper examines the effects of thermally reduced graphene oxide (rGO), incorporated in the titanium dioxide (TiO2) photoanode, on the performance of anthocyanin dye sensitized solar cells (DSSCs). While anthocyanin based DSSCs are cost effective, their efficiency tends to be low. In this study, rGO-TiO2 nanocomposites with different rGO weight fractions were synthesized. Their surface morphology was studied with Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Electrical conductivity of these nanocomposite layers were measured with the four-point probe method. The current-voltage characteristics of the DSSCs made with these nanocomposites along with anthocyanin dye from blackberries, a carbon counter electrode, and an Iodine based electrolyte were studied. It was found that the addition of rGO, at low weight fractions, increased nanocomposite conductivity, the solar cell short circuit current, and cell efficiency. Peak efficiency, increased by 45.7% of that with no rGO, was achieved with a photoanode layer containing 0.004 wt% rGO.

Effect of light intensity on the performance of silicon solar cell

This work, presents the intense light effect on electrical parameters of silicon solar such as short circuit current, open circuit voltage, series and shunt resistances, maximum power, conversion efficiency, fill factor. After the resolution of the continuity equation which leads to the solar cell photocurrent and photovoltage expressions, we use the J/V characteristic to determine the solar cell series and shunt resistances. The maximum electric power of the solar cell is determined using the curves of electric power versus junction dynamic velocity, and then, the fill factor and conversion efficiency are calculated. Light concentration and junction dynamic velocity effects on solar cell short circuit current, open circuit voltage, series and shunt resistances, electric power, fill factor and conversion efficiency are also studied. The study proved that with increase of illumination light intensity, the solar cell shunt resistances decreases whereas series resistance, short circuit current, open circuit voltage, electric power, fill factor and conversion efficiency increases. MARTIAL ZOUNGRANA, ISSA ZERBO, MAHAMADI SAVADOGO, SANNA TIEDREBEOGO, BOUBACAR SORO AND DIEUDONNE JOSEPH BATHIEBO

Synthesis of ITO nanoparticles at room temperature using plasma treatment process and use it as back reflector in a-Si flexible solar cell

At present main challenges of flexible thin film solar cell is its low initial efficiency. Use of suitable back reflector is one of the major ways of improving its performance. We synthesized ITO (Indium tin-oxide) nanoparticles by plasma treatment in a vacuum chamber using low pressure, high power technique at room temperature. We investigated the variation of size and shape of the nanoparticles with the process pressure, power density and process time and optimized it for solar cell application. Structural and optical characterization of the nanoparticles were carried out by FESEM and UV-VIS-NIR spectrophotometer. In this paper we introduce ITO nanoparticles as back reflector in silicon based thin film flexible solar cell. It has been found that by using suitable ITO nanoparticles it is possible to increase the solar cell short circuit current (Isc) by 8.9%. This may be due to the better light reflection from the back after application of nanoparticles. The maximum efficiency obtained with ITO nanoparticles back reflector is 8.27% which is 4.68% higher than that obtained without ITO nanoparticles at back.

Radial junction solar cells prepared on single crystalline silicon wafers by metal‐assisted etching

Radial junction solar cells have been proposed as an alternative device geometry to conventional planar solar cells with its remarkable electrical and optical performance. In this geometry, densely packed nano/micropillars allow minority carrier collection in the radial direction and shorten carrier diffusion length to p–n junction. Besides, reduced reflection from surface and increased light trapping in nano/micropillars enhance solar cell efficiency. In this study, photolithography and metal‐assisted etching (MAE) techniques are used to form well‐ordered silicon micropillar arrays; standard doping, passivation, and metallization steps are followed to form radial junction solar cells. The effect of micropillar length on optical and electrical performance of the solar cells have been investigated. We observed that optical reflection from solar cells surface decreased with increasing micropillar length, hence solar cell short circuit current (Jsc) and efficiency (ɳ) increased. Our best solar cell efficiency is 15.6% and this is one of the highest reported values obtained from the radial junction solar cells prepared by MAE technique.

EVA thin film with thermo- and moisture-stable luminescent copolymer beads composed of Eu(III) complexes for improvement of energy conversion efficiency on silicon solar cell

Luminescent beads composed of Eu(hfa)3(TPPO)2 (hfa: hexafluoroacetylacetonate, TPPO: triphenylphosphine oxide) in PMMA copolymer (polymethylmethacrylate- styrene and polymethylmethacrylate–trifluoromethylmethacrylate copolymers), PMMA–St–Eu and PMMA–TF–Eu have been reported for improvement of energy conversion efficiency on silicon solar cell. The PMMA–St–Eu and PMMA–TF–Eu beads are prepared using radical initiator AIBN (2,2-azobisisobutyronitrile) without BPO (Benzoyl peroxide) which promotes decomposition of Eu(hfa)3(TPPO)2. The emission properties of EVA (ethylene vinyl acetate) film with PMMA–St–Eu or PMMA–TF–Eu beads are characterized by the emission spectra and lifetimes. Thermo- and moisture-stabilities of the EVA films are performed under high temperature and high moisture condition (85°C85%RH). Increase percentage the solar cell short circuit current efficiency in the solar cell modulation using with EVA film containing PMMA–St–Eu beads with size in 70μm was estimated to 1.2%. Thermo- and moisture-stable PMMA–St–Eu and PMMA–TF–Eu beads for solar sealing film are demonstrated for the first time.

The effect of mode excitations on the absorption enhancement for silicon thin film solar cells

Periodic gratings on solar cell back reflectors are an alternative to randomly textured surfaces to provide absorption enhancement. Theoretically, it is impossible to excite quasi-guided modes at every wavelength for a given grating geometry and the broad band enhancement can only be achieved by strong absorption peaks at several wavelengths. Therefore, the critical issue is how to maximize the short circuit current using a limited number of discrete quasi-guided modes. In this work, a common dielectric-semiconductor-dielectric-metal solar cell structure is investigated. It is found that although the number of guided mode peaks has pronounced effect on the solar cell short circuit current, the geometry resulting in the highest short circuit current does not coincide with the geometry leading to the most supported modes. It is also found that high-Q modes are always resulted from global optimization for TE incidence, while low-Q modes are resulted for TM incidence on one-dimensional gratings without a dielectric spacer. Besides, a properly designed and configured dielectric spacer can provide >40% improvement in short circuit current. It is therefore suggested for solar cells with metallic back reflectors, dielectric spacer should be included, and the texture should be formed on the dielectric spacer itself rather than on the metal. Finally, the optimization of the mode quality is proved to be critical in all cases, in addition to the number of supported modes.

Correlation between P3HT inter-chain structure and Jsc of P3HT:PC[70]BM blends for solar cells

The nano-morphology of the active layer of organic solar cells has been studied extensively, as well as its link with the open circuit voltage of the device. However, considerably less attention has been dedicated to the relation between the active layer nano-morphology and the device short circuit current density. In this paper we study the relation between variations in the characteristics of the Poly-(3-hexylthiophene-2,5-diyl) (P3HT) chains and the resultant solar cell short circuit current density. We show that the lattice constant between two lamellar structure of P3HT inside the P3HT:Phenyl C70 Butyric Acid Methyl Ester (PC[70]BM) blend reduced as the PC[70]BM percent in weight was reduced in the analyzed range. The presence of nano-domains, which can be related to the intensity of the peak, also affects the short circuit current density. In this study the optimum value of the percent in weight of PC[70]BM, to obtain high short circuit current density was obtained for 1:0.5 ratio in the blend. The distance constant between the lamellar structure of P3HT for each blend made was directly extracted from the Bragg’s law in combination with the μ-XRD analysis. The results were correlated with the electrical characterization for each blend and we found that when decreases the distance between two lamellar structure of P3HT there is a better performance on photovoltaic devices.

Efficiency enhancement by mixed cation effect in dye-sensitized solar cells with PAN based gel polymer electrolyte

Dye-sensitized solar cells based on nano-porous TiO2 photo-anode and quasi-solid polymer (or gel) electrolytes are emerging as low cost alternatives to conventional inorganic photovoltaic devices. Although many attempts have been made in order to improve the relatively low power conversion efficiencies of these solar cells, to our knowledge there are very few reports aimed at using a binary system of two different iodide salts toward efficiency enhancement in these cells. In this paper we report for the first time in detail, the effect of using a binary iodide salt mixture with different size cations on the efficiency enhancement in dye sensitized solar cells with polyacrylonitrile (PAN) based gel polymer electrolyte and suggest a possible mechanism for this enhancement, based on short circuit photocurrent which is directly related to the iodide ion concentration [I-]. The gel electrolyte was made of PAN, ethelene carbonate (EC), Propylene carbonate (PC), salt mixture and I-2. The binary iodide salt mixture consists of potassium iodide (KI) and Tetra propyl ammonium iodide (Pr4NI). Although the gel electrolyte with 100% (w/w) KI exhibited the highest overall ionic conductivity at room temperature, it showed the lowest iodide ion (I-) contribution to conductivity. On the other hand, the electrolyte with 100% (w/w) Pr4NI exhibited the lowest overall ionic conductivity but had the highest iodide ion(I-) contribution. The dye-sensitized solar cells of configuration Glass/FTO/TiO2/N-719 Dye/electrolyte/Pt/FTO/glass were fabricated using the gel electrolytes of different salt ratios and with nanoporous TiO2 electrode sensitized with Ruthenium dye (N719). With identical electrolyte compositions, the solar cell with 100% (w/w) KI showed an efficiency of 4.98% and the cell with 100% (w/w) Pr4NI showed an efficiency of 4.47%. However, the cell with the mixed iodide system, 16.6% (w/w) KI + 83.4%(w/w) Pr4NI showed the highest efficiency of 5.36% with maximum short circuit current density (J(SC)) of 13.79 mA cm(-2), open circuit voltage (V-OC) of 679.10 mV and a fill factor of 57.25%. The variation of efficiency (eta) with iodide ion concentration [I-] follows the same trend as the J(SC) which appears to be governed by the iodide ion conductivity of the gel electrolyte. The dependence of the short circuit photocurrent and the open circuit photovoltage on the cation type generally agrees with reported data for related systems. However, the occurrence of a maximum in the solar cell efficiency and short circuit photocurrent at 16.6% (w/w)10 + 83.4% (w/w) Pr4NI salt composition is an important finding. The efficiency enhancement of about 8% achieved by employing the binary iodide mixture in the gel electrolyte instead of a single iodide salt, could be utilized for achieving efficiency enhancement in many dye sensitized solar cell systems based on polymeric, gel or solvent electrolytes.

Spatial mapping of photocurrents in organic solar cells comprising wedge-shaped absorber layers for an efficient material screening

In this work we present a facile route to an efficient experimental screening of new materials and to a layer thickness optimization in solution processable polymer photovoltaic devices. Therefore, we developed a method of fabricating solar cells with wedge-shaped active layers. Spatially resolved measurements of the solar cell short circuit current densities for different light absorbing polymers under white light allow for a quick conclusion about the optimum active layer thickness within the device. To demonstrate the generality of this experimental approach we studied the well-established photoactive blends from poly-(3-hexylthiophene-2,5-diyl) and [6,6]-phenyl C61-butyric acid methyl ester (P3HT:PC61BM) or poly[N-9′-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] and [6,6]-phenyl C71-butyric acid methyl ester (PCDTBT:PC71BM). The short circuit current densities are in very good agreement with optoelectronic device simulations and results from sample-by-sample measurements.

Extended description of tunnel junctions for distributed modeling of concentrator multi-junction solar cells

One of the key components of highly efficient multi-junction concentrator solar cells is the tunnel junction interconnection. In this paper, an improved 3D distributed model is presented that considers real operation regimes in a tunnel junction. This advanced model is able to accurately simulate the operation of the solar cell at high concentrations at which the photogenerated current surpasses the peak current of the tunnel junction. Simulations of dual-junction solar cells were carried out with the improved model to illustrate its capabilities and the results have been correlated with experimental data reported in the literature. These simulations show that, under certain circumstances, the solar cell's short circuit current may be slightly higher than the tunnel junction peak current without showing the characteristic dip in the J– V curve. This behavior is caused by the lateral current spreading toward dark regions, which occurs through the anode/p-barrier of the tunnel junction.

Metal Assisted Surface Texture for String Ribbon Solar Cells and Modules

This work presents metal assisted etching for surface texturing of industrial size String Ribbon wafers. Palladium serves as a catalyst for chemical etching in an aqueous solution containing hydrofluoric acid and nitric acid. String Ribbon solar cells textured by metal assisted etching show a decreased effective reflection ΔReff = 16%rel compared to untextured solar cells. The decreased reflection results in a solar cell efficiency increase Δηcell = + 0.4%abs. The improvement in solar cell efficiency is mainly due to an increase ΔJsc = + 0.9 mA/cm2 in the average solar cell short circuit current density Jsc and an increase ΔFF = 0.7%abs in fill factor FF. Due to enhanced optical coupling, the efficiency increases additional Δηmodule ≈ 0.1%abs after encapsulation of the cells behind glass.

Microcrystalline silicon thin film solar cells with microcrystalline silicon carbide window layers and silicon absorber layers both prepared by Hot‐Wire CVD

AbstractMicrocrystalline silicon carbide (μc‐SiC:H) window layers prepared by Hot‐Wire Chemical Vapor Deposition (HWCVD) were applied in thin film silicon solar cells with microcrystalline silicon (μc‐Si:H) absorber layers. The intrinsic μc‐Si:H absorber was prepared by HWCVD or Plasma Enhanced Chemical Vapor Deposition (PECVD) over a wide range of crystalline volume fractions. With both types of absorber layers high solar cell short circuit current densities (jSC) can be obtained due to the highly transparent μc‐SiC:H window layer and better optical matching. Using the μc‐Si:H absorber prepared by HWCVD yields an additional improvement in the open circuit voltage (VOC) of about 20 mV. A 1 μm thick μc‐Si:H cell was obtained with VOC = 549 mV and jSC = 25.6 mA/cm2 resulting in an efficiency of 9.2%. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Temperature Effects on the Electrical Performance of Large Area Multicrystalline Silicon Solar Cells Using the Current Shunt Measuring Technique

The temperature effects on the electrical performance of a large area multicrystalline silicon solar cell with back-contact technology have been studied in a desert area under ambient conditions using the current shunt measuring technique. Therefore, most of the problems encountered with traditional measuring techniques are avoided. The temperature dependency of the current shunt from 5ºC up to 50ºC has been investigated. Its temperature coefficient proves to be negligible which means that the temperature dependency of the solar cell is completely independent of the current shunt. The solar module installed in a tilted position at the optimum angle of the location, has been tested in two different seasons (winter and summer). The obtained solar cell short circuit current, open circuit voltage and output power are correlated with the measured incident radiation in both seasons and all results are discussed.

Temperature Effects on the Electrical Performance of Large Area Multicrystalline Silicon Solar Cells Using the Current Shunt Measuring Technique

The temperature effects on the electrical performance of a large area multicrystalline silicon solar cell with back-contact technology have been studied in a desert area under ambient conditions using the current shunt measuring technique. Therefore, most of the problems encountered with traditional measuring techniques are avoided. The temperature dependency of the current shunt from 5ºC up to 50ºC has been investigated. Its temperature coefficient proves to be negligible which means that the temperature dependency of the solar cell is completely independent of the current shunt. The solar module installed in a tilted position at the optimum angle of the location, has been tested in two different seasons (winter and summer). The obtained solar cell short circuit current, open circuit voltage and output power are correlated with the measured incident radiation in both seasons and all results are discussed.

Electrical Performance Study of a Large Area Multicrystalline Silicon Solar Cell Using a Current Shunt and a Micropotentiometer

In this paper, a new technique using a Current Shunt and a Micropotentiometer has been used to study the electrical performance of a large area multicrystalline silicon solar cell at outdoor conditions. The electrical performance is mainly described by measuring both cell short circuit current and open circuit voltage. The measurements of this cell by using multimeters suffer from some problems because the cell has high current intensity with low output voltage. So, the solar cell short circuit current values are obtained by measuring the voltage developed across a known resistance Current Shunt. Samples of the obtained current values are accurately calibrated by using a Micropotentiometer (μpot) thermal element (TE) to validate this new measuring technique. Moreover, the solar cell open circuit voltage has been measured. Besides, the cell output power has been calculated and can be correlated with the measured incident radiation.

Experimental analysis and modeling of the IV characteristics of photovoltaic solar cells under solar spectrum spot illumination

In this paper, some models that have been put forward to explain the characteristics of a photovoltaic solar cell device under solar spot-illumination are investigated. In the experimental procedure, small areas of the cell were selected and illuminated at different solar intensities. The solar cell open circuit voltage (Voc) and short circuit current (Isc) obtained at different illumination intensities was used to determine the solar cell ideality factor. By varying the illuminated area on the solar cell, changes in the ideality factor were studied. The ideality factor obtained increases with decreasing illumination surface ratio. The photo-generated current at the illuminated part of the cell is assumed to act as a dc source that injects charge carriers into the p–n junction of the whole solar cell while the dark region of the solar cell operates in a low space charge recombination regime with small diffusion currents. From this analysis, a different model of a spot illuminated cell that uses the variation of ideality factor with the illuminated area is proposed.