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32nd European Photovoltaic Solar Energy Conference and Exhibition; 76-79, We have succeeded in observation of photoresponsivity of BaSi2 film grown on Si by vacuum evaporation method, raising its promising application in high efficiency thin film solar cell. Photocurrent was observed at photon energies larger than 1.28 eV, which corresponds to band gap of evaporated BaSi2 film. The effect of deposited substrate temperature on photoresponsivity was also investigated. The obtained results indicate that BaSi2 film grown at substrate temperature of 500 oC, which is single phase and free from crack, shows the best photoresponsivity. Maximum value of photocurrent was obtained at photon energy of 1.9 eV, corresponding to an external quantum efficiency of 22% under reverse applied voltage of 2 V.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 223-227, Series-parallel interconnection of tandem cells is an alternate approach to standard monolithic interconnection design. By matching string voltage instead of cell current, a broad range of top cell bandgaps can be effectively combined to produce near-ideal efficiency. Annual energy yield using spectrum and weather data collected by NREL was simulated for tandem module designs. The series-parallel approach is extremely tolerant of spectrum and temperature variation, achieving a simulated yield of >99% of the ideal four-terminal tandem for a given bandgap. Importantly, a wide range of bandgaps (1.4eV to 2.0 eV) also achieved energy yields greater than 95% of that achieved for the ideal bandap (~1.65eV). The series-parallel approach provides broad design flexibility, particularly for the top cell, to enable relatively free choice of the best material for efficiency and manufacturability rather than being constrained solely by current matching.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 11-14, In this contribution, we present a modelling tool allowing to efficiently optimize the design of solar cells and modules in order to maximize the power output for different application scenarios and reduce the lateral electrical losses in the transparent conducting electrodes (TCE). We investigate the use of combined metal grids and conductive polymers as well as silver nanowire materials for enhancing the lateral conductivity of the TCEs. These promising new TCE materials provide the option to tune the conductivity and transparency, therefore a smart electrode layout choice has to be made for a specific application. We present the optimization and parameter sweep calculations to illustrate the design and customization freedom.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 260-262, Amorphous silicon carbide in various forms, thin films or bulk structures, is a longer period used in microelectronics, power electronics, sensors and mechanical engineering. Thin films of n-doped amorphous silicon carbide (a-SiC:H) in combination with crystalline silicon representing heterostructure for the solar cells were object of this study. AC measurements and subsequent analyzes were used to estimate the impact of Xe and neutron irradiation on electrical properties of studied heterostructure. Impact of Xe and neutron irradiation has been quantified by using AC equivalent circuits and the corresponding voltage dependence of AC equivalent circuit elements. The influence of Xe-ions and neutron bombardment of a-SiC:H/c-Si heterostructure which resulted in the changes of elements of equivalent circuit – parallel resistance and capacitance – have been identified and explained.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 205-208, Light management in tandem solar cells has gained much attention for achieving high conversion efficiency. Here, we investigate the effects of nanostructured interfaces on the optical properties such as optical coupling of luminescent tandem solar cells by using electromagnetic wave simulation. We calculated the angledependent Fresnel coefficients at the nanostructured interface in lead-halide perovskite/c-Si tandem solar cells. The simulation results show that the luminescent coupling between the perovskite and c-Si sub-cells can be improved using a short-period nanostructured interface. A luminescent coupling efficiency greater than 95% is obtained for the nanostructured interface with height less than 1 µm.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 36-38, In this work, the influence of different growth conditions of the cap layer of quantum dots on the figures of merit of Intermediate Band Solar Cells is investigated. The optimized quantum dot capping procedure led to improvements in all figures of merit, namely by 7.7% in short circuit current density, 41% in open circuit voltage, 29% in fill factor and 85% in efficiency, when the temperature of the In flush process increases from 630 to 700 ºC. We attribute the improvement in the devices’ performance to a lower density of Shockley-Read-Hall recombination centers, as the analysis of the dark current points out. Furthermore, the short circuit current density raises by 6.9% when compared to the control solar cell (without quantum dots) due to subbandgap absorption.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 183-186, STR has recently developed new non-EVA encapsulants for PV modules based on polyolefin elastomers (POE’s). These materials have many advantages compared to traditional EVA based encapsulants like improved thermal and chemical stability, minimized corrosive potential, lower moisture vapor transmission rate (MVTR), improved electrical properties and PID resitance [1]. However, some similarities remain, like the need for a curing approach where the encapsulant is transformed from a thermoplastic into an elastomer during lamination. In this regard, lamination cycle optimization is required in order to obtain a good compromise between sufficient curing and optimal performance and reliability of the correspondent PV module. Special focus will be place on measuring the main properties that could be affected by poor cure levels like i) creep resistance, ii) adhesion to glass, iii) adhesion retention after DH85/85 and iv) light transmission. Lamination cycle times similar to standard EVA encapsulants are desirable.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 242-244, This paper describes a junction property of nanoparticle(NP) embedded SiO2/Si. P+Si NPs and/or combination with Ag particles were tested. A liquid source SiO2 layer was obtained using Perhydropolysilazane (PHPS), which shows good passivation property on Si. After spin coating deposition, NP embedded SiO2 layers were obtained using a hot steam annealing at 600C. The p+SiNPs embedded SiO2/Si(n) hetero structure showed rectifying property. A forward bias current under illumination was lower than the dark, indicating a memory effect, which can be explained by hole trap of floating Si NPs in the SiO2 film. Using this property, selective contact was tested using the combination of p+ Si NP and Ag particle. An Ag particle embedded SiO2 was an ohmic contact. On the other hand, the SiO2 film including both p+Si NPs and Ag particle showed rectifying property with no memory effect. In addition forward bias current increased by illumination.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 99-104, In this paper, two developments targeted at reducing the production cost of back-contact modules are presented. The first cost reduction potential is realised by replacing the conductive copper layer with aluminium with a very thin and locally applied copper coating using cold spray technology. This results in a 2% PV module cost saving while also meeting industrial requirements for production speed and reduction of contamination. Prototype mini-modules manufactured using this method have shown very good performances and passed selected IEC reliability tests (Damp Heat and Thermal Cycling).The second cost reduction comes from reduction of encapsulant usage. By using powder coating technology, encapsulant thicknesses below 100 microns can be achieved. This not only results in the reduction of encapsulant usage as compared to standard modules, but it also increases production flexibility. Application of powder coated encapsulant results in a cost reduction of 1%. An additional cost advantage of the implementation of thinner encapsulants is a reduction of conductive adhesive of at least 60%, which can result in an additional 2% cost reduction.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 25-27, In this paper, we introduced a novel three-dimensional shell based framework, coupling the Phantom node method to study complex fracture patterns in PV Silicon cells. The developed framework has been applied to study complex fracture patterns observed in a fatigue test carried out in [15]. Based on the estimated crack opening displacement from the computational model, we are able to correlate the reasons for the development of inactive areas leading to power loss. Therefore, we report that the critical crack opening displacements results in large resistances along the crack lines, finally leading to electrically inactive areas depending on the fracture pattern.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 123-126, With the current trend in the photovoltaic industry towards thinner solar cells and four (or more) busbar modules, the cell-interconnection/stringing process is becoming more challenging. Besides the possibility of damaging solar cells during the soldering process itself, thermal and mechanical stresses within this process step are also assumed to induce cracks, which are occurring later during the operation of the PV module under certain environmental conditions, such as heavy snow or wind loads and excessive temperature fluctuations. In order to produce reliable high-quality PV modules at sound costs, it is necessary to minimize the stress on the solar cells during the manufacturing process. Within this study Raman spectroscopy is utilized to analyze the stress of solar cells induced by the interconnection process. Besides investigations on manually soldered solar cells, also industrially interconnected solar cells were evaluated. Here, an industrial soldering as well as a glueing/bonding interconnection technique was analyzed. All investigated solar cells are based on three busbars technology.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 173-175, This contribution describes thin-film barrier coatings to enhance the stability of silicon thin-film solar modules. Thin-film barriers are applied to protect the modules from degradation in humid environment. Demonstrator modules were exposed to indoor and outdoor tests to evaluate failure modes by electrochemical corrosion during operation. Test results reveal some major failure modes, but we demonstrate long lifetimes under operational conditions for certain modules without conventional encapsulation. These modules without conventional encapsulation showed less than 1% relative degradation during 1000 hours of damp-heat tests with light exposure at open circuit voltage. These promising results will guide the way to new encapsulation concepts for longer lifetimes and/or new low-cost concepts. This approach might be applied to any thin-film technology and will be an important aspect for consumer electronics with less strict requirements for very long-term operation.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 66-68, In this article, we demonstrate a patch, which contains upconverting crystals of Gd2O2S:Yb3+, Er3+ mixed with a UV curable gel, integrated with a textured back-reflector that can be externally affixed to a bifacial thin-film silicon solar cell. The patch serves to provide the benefit of light trapping as well as spectrum upconversion to the solar cell fabricated on a flat substrate. Upconverting patches with different textures were studied for their effectiveness in enhancing the short-circuit current density of the solar cell and for the relationship between the current enhancement and the intensity of the incident light. The upconverting patch is shown to enhance the solar cell performance and offers a new stick-on technique to apply upconversion-based strategies to existing solar cells. The photogenerated short-circuit current densities of the solar cell show a power-law dependence on the illuminated laser light intensity when an upconverter patch is attached to the solar cell (exponent 1.5-1.6) while a linear dependence is observed for the solar cell without the upconverter patch.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 39-41, Strong broadband absorption can be achieved in solar cells with only 25 nm thick amorphous germanium nanoabsorbers by taking advantage of the optical resonances generated between the electrodes of the devices. Two different configurations of such resonant-cavity-enhanced a-Ge:H solar cells have been investigated: When exploiting lowest-order resonances, broadband absorption enhancement is obtained, enabling a short circuit current density of more than 20 mA cm-2 in single cells and 12 mA cm-2 in tandem devices. However, this requires the use of an extremely thin resonator and hence thin doped layers. This complicates electrical optimization, as too thin doped layers lead to poor charge carrier extraction. The approach presented here aims to solve this problem by specifically designing devices for application in a-Si:H/a-Ge:H tandem cells. In this case, only near-infrared light needs to be absorbed. This allows utilization of longer cavities producing second-order resonances inside the relevant spectral range. As a result, thicker doped layers can be used, which improves the electrical device characteristics. In this contribution, we identify basic design rules to optimize the infrared absorption of such devices.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 1-4, This paper reports on a novel and highly innovative technology to interconnect back-contact cells. First a background section explains the currently developed interconnection technologies. Then our novel concept is introduced: interconnection of the cells is achieved with a woven fabric, combining both conductive wires, needed for the interconnection, and insulating wires, crucial to avoid shunting between both polarities at the backside of the cell. Weaving also allows out-of-plane stress relief features. In the third section, we explain that our technology combines the advantages of multi-wire interconnection such as low-stress and reduced resistive losses with known and low-cost materials of traditional module assembly. We demonstrate that the technology can be tuned broadly in terms of costs and resistive losses using an optimized interconnection pattern. These loss simulations are also validated with the measured additional resistance in IBC test samples. Finally, first functional proof-of-concept with MWT cells as well as IBC cells have been fabricated.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 152-154, We report on the synthesis of colloidal CuIn3Se5 nanocrystals, for the first time, using simple solutionbased method. The cubic phase CuIn3Se5 nanocrystals grow, in the shape of nanoparticles, with an average diameter of 35 nm. The band gap of the grown CuIn3Se5 nanocrystals is determined to be 1.33 eV and thus can be suitable for inkcoated thin film solar cells.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 28-31, Heterojunction 50-layer-stacked Ge quantum dot solar cells (QDSCs) were fabricated via molecular beam epitaxy using a strain-compensation technique. Si1-xCx materials consisting of a Si matrix with a small amount of carbon (~0.05%) were used as strain-compensating layers (SCLs). In the 50-layer-stacked Ge QDs, large coalesced islands with a density of 4.0 108 cm-2 were observed for QDs stacked with Si spacer layers, whereas the formation of coalesced islands was effectively suppressed for QDs stacked with Si1-xCx SCLs. The external applied bias voltage dependence on the short circuit current was calculated from external quantum efficiency measurements. This study revealed that the carrier collection efficiency Ge/Si1-xCx QDSCs was superior to Ge/Si QDSCs, possibly due to the reduction of non-radiative recombination centers associated with coalesced islands. As a result, the open circuit voltage increased from 0.38 V for Ge/Si QDSCs to 0.42 V for Ge/Si1-xCx QDSCs.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 228-231, The optical properties of InAs quantum dots with GaAsSb cladding layers of different alloy composition have been studied by photoluminescence techniques. Power-dependent photoluminescence data suggest a transition from type-I to type-II could be achieved by GaAsSb cladding layer at Sb composition around 11% for these samples. At low Sb compositions, good crystal quality was evident from temperature-dependent photoluminescence, with a small energy barrier inferred, while high-level dislocation and defects exist under higher antimony contents. The results show the interplay between the tendency of Sb in the buffer layer to blue-shift the emisison, whilst Sb in the capping layer red-shifts emission. With the additional presence of strain relaxation through formation of defects at higher Sb content, it is clear that designing a structure to achieve a zero valence band offset must take into account the strain distribution throughout the structure.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 169-172, Different approaches like round wire interconnectors, shingled or back-contact cells have been presented in the past to improve the cell-to-module efficiency ratio by reducing the shading losses of interconnector ribbons. We present a new cell interconnector design based on a triangular cross section to further improve modules based on interconnector ribbons. We analyze the optical behavior of the concept and compare it with rectangular ribbons and round wire interconnectors. An evaluation of the new concept using optical ray tracing is performed. Results show an advantage in optical performance of 2.35% of the new concept compared to standard interconnector ribbons under perpendicular irradiation as well as 1.94% compared to round wires. An analysis using irradiation data (DNI) shows a superior optical performance of the TriCon-Concept. We find that in an elevation tracked module using TriCon 2.32% more light reaches the cell surface over the year compared to rectangular interconnectors (5BB) and 2.02% compared to round wires.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 15-19, Multi-wire interconnects are currently being commercialized by several large PV companies to replace the traditional flat-tabbed busbars. Advantages of multi-wires include reduced silver usage, lower grid resistance, higher tolerance to cracks, and improved optics. This paper evaluates the optical losses of a multi-wire module and compares them to those of busbar modules. It includes the first application of ray tracing to multi-wire modules and finds that the results agree reasonably well with some published experimental mini-modules with similar wires and cells. The simulations also indicate that the optical advantage of multi-wire modules should increase slightly as the angle of incidence changes from 0 to 80°, whether for cells with random pyramids or isotexturing. We also find that the effective optical width of the wires increases as the number of wires increases, and that it is approximately 60% of the wire diameter for typical multi-wire applications; this effective width is significantly greater than what is calculated from a geometrical assessment of a singe wire.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 48-52, Results of an electroless displacement process for the deposition of inexpensive solderable metal on physical vapour deposited (PVD) aluminum are presented. The dip – rinse – dry processing sequence for electroless metal deposition on Al is simple and easy to use because it does not harm the SiN antireflection coating and the screen-printed Ag metallization on the cells’ front side. Hence, finished cells can entirely be immersed into the electrolyte. The deposited metal layer is highly porous, but forms a massive alloy with common Sn/Pb/Ag solder at low temperature of 245 °C in the presence of no-clean flux. Because the molten alloy wets Al and copper well, we obtained strong solder joints for Sn/Pb/Ag coated copper ribbons on Al. The measured average 90° peel forces of ribbons soft soldered to thermally evaporated Al on shiny etched silicon and on the rear of alkaline textured monocrystalline Si PERC solar cells were up to 3.1 and 2.2 N per mm ribbon width, respectively. These values exceed 1 N/mm that is specified by the standard DIN EN 50461. Climate tests on single-cell glass-glass modules yielded 4.1 and 7.7 % power degradation after 200 thermal cycles from -40 °C to 85 °C and after 1000 h under damp-heat conditions at 85 °C and 85 % relative humidity, respectively. We attribute the too high power degradation after damp-heat test to residuals of the acidic flux which was used for soldering the cells in this first, older version of the developed technology.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 253-255, PC1D6, as well as PC1D, allows fitting I-V curves with the double-exponential approach. In addition, it allows implementing up-to-date physical models for band-gap narrowing (BGN) and other parameters. We use PC1D6 together with an analytical iterative I-V fitting approach to check the influence of physical models on the assignments to parameters in fitting data of external-quantum efficiency (EQE) and I-V measurements. Data relevant to an actual PERC solar cell are exploited. We find that the chosen physical model only determines the SRH-lifetime value to be assigned in the I-V fits performed with PC1D6.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 94-98, The interconnection of silicon solar cells by soldering causes thermomechanical stress due to different coefficients of thermal expansion of the materials involved, especially copper and silicon. In contrast to the current standard interconnection technology, using three to five flat ribbons to be soldered on continuous or segmented busbars on the solar cells front side and on large contact pads on the solar cells rear side, the Multi Busbar concept uses twelve to fifteen round solder coated copper wires to be soldered on a large number of small contact pads for each polarity. In this paper we present two finite element models, one for a solar cell with a common busbar-based interconnection and a second one for a solar cell using the Multi Busbar interconnection approach to analyze and compare the distribution of the thermomechanical stress induced by the cell interconnection. The results show only a slight vertical deformation of a contacted solar cell of 0.4 mm for the three busbar design and 2.2 mm for the Multi Busbar interconnection technology due to the non-symmetric pad layout and the aluminum metallization on the rear side. However, most parts of the copper interconnector (ribbons and wires) are plastically deformed because the tensile stress exceeds the yield strength of 100 MPa. In addition, the results indicate that there is only slight tensile stress in most parts of the silicon solar cell after the soldering process. For both interconnection technologies we detect local stress peaks and, on the rear side of the solar cells near the outermost contacts, we determine areas where the tensile stress reaches levels above 200 MPa that potentially cause defects.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 267-269, Titanium Oxide has recently been demonstrated as an electron selective layer because of its asymmetric band offsets with conduction and valence band of silicon [1]. In order to be used as an electron extracting layer in non P-N junction solar cells TiO2 thin films also need to passivate the silicon dangling bonds at the interface. In this work we report reduction of surface recombination velocity by TiO2 films deposited by Thermal Atomic Layer Deposition (T-ALD) and Plasma Atomic Layer Deposition (P-ALD). The as deposited sample with TiO2 deposited by thermal ALD showed an implied VOC of 568 mV and a high surface recombination velocity (SRV) of more than 5000 cm/s. The post annealing of this samples yielded a high implied VOC of 658 mV and surface recombination velocity of less than 120 cm/s.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 148-151, Sequential deposition methods for preparing CH3NH3PbI3 film are becoming increasingly popular when considering processing perovskite solar cells (PSCs) under relative relaxed conditions. Correspondingly, the problem concerning PbI2 residue receives special attention due to its deterioration to device performance reproducibility and long-term stability. In this work, we demonstrate an effective sequential thermal evaporation strategy in low vacuum (STELV) to fabricate PbI2-free CH3NH3PbI3 film with full coverage and good crystallization. Through a comparative study, it is observed that STELV has a stronger ability to control morphology and thickness of CH3NH3PbI3 film, alone with good uniformity. Moreover, we demonstrate that remaining PbI2 film should be responsible for the poor PSCs thermal stability.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 158-164, Conversion of energy of beta-particles into electric energy in a p-n junction based on direct-bandgap semiconductors, such as GaAs, is analyzed considering realistic semiconductor system parameters. An expression for the collection coefficient, Q, of the electron-hole pairs generated by beta-electrons is derived taking into account the existence of the dead layer. We show that the collection coefficient of beta-electrons emitted by a 3H-source to a GaAs p-n junction is close to 1 in a broad range of electron lifetimes in the junction, ranging from 10-9 to 10-7 s. For the combination 147Pm/GaAs, Q is relatively large (≥ 0.4) only for quite long lifetimes (about 10-7 s) and large thicknesses (about 100 μm) of GaAs p-n junctions. For realistic lifetimes of minority carriers and their diffusion coefficients, the open-circuit voltage realized due to the irradiation of a GaAs p-n junction by beta-particles is obtained. The attainable beta-conversion efficiency in the case of a 3H/GaAs combination is found to exceed that of the 147Pm /GaAs combination.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 256-259, Selectively reflecting Bragg structures comprised of simple quarter-wave coatings offer a mechanism to further improve upon the enhancements achieved with plasmonic enhanced luminescent down shifting (pLDS) layers. Theoretical modelling using a transfer matrix approach demonstrates the ability of simple one- or two-layer reflecting structures to offer enhancements in the performance of a PV device consisting of a 9μm-90μm pLDS layer deposited on top of a silicon cell. Enhancements of 10.8% - 21% are reported, with the enhancement depending upon a number of design parameters (number of layers, spectral region of maximum performance and the optical properties of the constructing materials). Design of thin film enhanced pLDS layers are presented as well as establishing initial design parameters for these enhanced structures.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 80-84, Solar grade III-V substrate is a virtual III-V/Si substrate consisting of high crystalline quality III-V semiconductor with direct III-V/Si heterojunction on Si substrate, which can be the key to realize high efficiency Si based tandem solar cell at a competitive cost. Recently, corrugated epitaxial lateral overgrowth (CELOG) was used to fabricate high quality InP on Si with atomically abrupt interface. In this work CELOG based fabrication technology of solar grade InP substrate comprising n-InP/p-Si type II heterojunction or n+-InP/n-Si ohmic heterojunction was developed in hydride vapor phase epitaxy (HVPE) reactor. The structural, optical and electrical properties of the InP/Si heterojunctions were systematically studied by scanning electron microscopy (SEM), photoluminescence (PL), transmission electron microscopy (TEM) and current-voltage (I-V) techniques. Photodiode devices based on solar grade InP/Si substrate were demonstrated. Exploitation of the solar grade III-V substrate technology will pave the way to achieve the Si PV cell with efficiency beyond the level of 30% at a competitive cost.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 249-252, Thin-film solar cells employ a back reflector (BR) for a more efficient use of the long wavelength light. This paper deals with the prospect of using indium tin oxide (ITO) nanoparticle (NP) as back scatterer/reflector in single junction amorphous silicon solar cells. As the ITO NP’s have comparatively low dissipative loss and tuneable optical properties. NP’s of ~200nm size is developed on the back side of the complete a-Si solar cell by deposition of ~20-30nm thick ITO by DC magnetron sputtering followed by hydrogen plasma treatment in PECVD. Various characterizations like FESEM, TEM and AFM are performed to analyse the morphology, chemical composition, optical characteristics of the NP’s. The p-i-n structured solar cell with 8.17% of efficiency is fabricated in a conventionally used cluster tool PECVD system. The short circuit current (Isc), open circuit voltage (Voc) and fill factor (FF) of the solar cell are 13.17mA, 0.885V and 70.10% respectively. ITO nanoparticles at the back surface of the solar cell significantly enhances the short circuit current by ~9.5% to 14.42mA, (Voc-0.884V, FF-70.82% ) and due to that increase the overall efficiency of the device reaches to 9.02%. The results reported show a novel method of enhancing short circuit current of a-Si based solar cells which will be explored for further enhancement of the effect by varying nanoparticle size.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 155-157, TCOs are usually deposited using sputtering or chemical vapor deposition, which have a yield of typically 50-75%. The sol gel method does not need low pressure and can be done with a high precursor yield in the range of 90 – 100%. Sol gel enables also the TCO function as a planarization or texturisation layer. Major drawback and cost driver is the annealing step. The annealing process parameter requirements are highly related to the ingredients and their preparation. These factors can be tuned to get both a layer of high quality and a fast and cost effective process. We present here an annealing study with in-situ conductivity measurement to monitor the effect of temperature ramping, process time, process gas, etc. For ITO, we obtained a sheet resistance of 20 Ohm/sq for layers below 100 nm in thickness as a best result. Furthermore, the annealing process can be tuned to be within a couple of minutes.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 180-182, We report the 273W anti-glaring module with curved-frame structure and 0.85mm thickness glass. The optical simulation shows the reflectivity of curved module received by inspector is reduced 96.79% than flat panel by using Tracepro software. And the outdoor anti-glaring performance of this anti-glaring module has reached larger than 60% improvement than flat panel. However, the outdoor energy yield of anti-glaring module is lower (-0.19%) than flat panel. But the anti-glaring module still has a lot of benefits, like more efficient land usage, drainage and light weight (10.5 kg) which can be moved and installed quickly.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 115-117, We review the available models for Lambertian optics in Si solar cells with surface texture. We check these models in devices having same structure and assignments to transport and optical parameters and different depth. Based on the check, we infer that, in Si solar cells with surface texture, the standard model for Lambertian optics, where the light-propagation angle is equal to 60° at all passes of light across the considered device, is more reliable than the remaining models, in the case of thin devices.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 209-211, In a hot carrier solar cell the collection of hot carriers requires electrical contacts with a narrow energy pass bandwidth, known as energy selective contacts to minimise energy lost as heat via the increase in entropy at the contacts. However due to the large effective mass of holes compared to electrons majority of the energy from absorbed photons are taken up by electrons, 94.3% in the case for an InAs absorber. Therefore a carrier selective contact can be used rather than an energy selective contact for the collection of holes in a hot carrier solar cell with minimal energy loss from the hot hole population cooling. Copper iodide (CuI) has been identified as a material which can potentially be used to collect holes. Preparation of CuI films is done by solution processes, dissolving CuI powder in a solvent and spin coating on the substrate. The material properties such as optical properties, crystal structure and film morphology are studied in the context of its suitability for use as an electron blocking and hole collecting layer for the hot carrier solar cell.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 196-199, AiSoVol project consists on the development, manufacturing and testing in a controlled environment of a new concept of photovoltaic modules, conceived for facilitating their use as architectural elements. Thus, the modules will be fabricated by encapsulating its constituent electrical elements (cells and interconnections) with lamination techniques at low curing temperatures and using transparent thermoplastic instead of tempered glass, as well as binding materials structurally strengthened by a grid made of high-tenacity yarns, such as the ones used in sail technologies and thus avoiding the need for aluminum frames. This type of solution will provide, due to the nature of the constituent materials, lighter PV modules which can adapt easier to different surfaces. In this paper the methodology followed to define a suitable lamination process compatible to obtain reliable AiSoVol photovoltaic modules is described. Results achieved from materials and processes validation will pave the way for manufacturing the prototypes in next project phase.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 245-248, The optical path length and the intensity of the incident light reaching the solar cell could be enhanced by incorporating antireflective and light scattering nanostructures. In this work, the upright periodic nanopyramid structures were fabricated on the surface of a glass substrate using UV nanoimprint lithography, which was employed in this case as a protective layer for solar cells, in addition to its antireflection coating function. The haze value was significantly increased for upright nanopyramid patterned glass, especially, in the wavelengt h range 300-600 nm, which implies that strong light scattering by upright nanopyramid structure. By replacing a bare protective glass with upright nanopyramid patterned glass, the power conversion efficiency of the monocrystalline Si and commercially made polycrystalline Si solar cells were substantially enhanced about 10.89% and 8.22% due to the scattering and prolong the optical path length by the upright nanopyramid structures. In addition, the surface of the patterned glass exhibited hydrophobic propert ies due to the surface nanostructures and the self-assembled monolayer coating. The high hydrophobicity provided the solar cell with a self-cleaning functionality.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 270-273, In this work, the impact of material quality i.e. impact of minority carrier lifetime on SiC/Si3N4/SiO2 passivated 10μm thick rear contact SiGe solar cell have been obtained. Result shows, the photovoltaic parameters are less affected by minority carrier lifetimes (). Also, as changes from 10-2 s to 10-5 s, change in JSC, VOC, FF and PCE are 0.4%, 0.5%, 2.2% and 3.2%, respectively. Further, the application of rear contact SiGe solar cell for concentrator photovoltaic (CPV) has also been discussed. At 300 K operating temperature, we have obtained the open circuit voltages 627mV, 646mV and power conversion efficiencies of, 15.7%, 16% at 5-sun (0.5 W.cm-2) and 10-sun (1W.cm-2) conditions, respectively for SiC/Si3N4/SiO2 coated SiGe cell. This, results in 6.8 % and 8.8% higher power conversion efficiency (PCE) at the concentration levels of 5, 10 suns compared to 1-sun condition (14.7%, PCE). Also, under 10-sun illumination, 9the PCE of 16.4% and 16.1% at 20oC and 25oC temperature, respectively have been obtained. All the simulation have been done using Silvaco atlas device simulator.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 20-24, Very reflective back side reflectors directly below the active region of a solar cell alter the photon absorption and carrier collection dynamics in a manner that can be exploited for enhanced efficiency. The enlarged optical path increases the short circuit current, and the confinement and (re)absorption of the photoluminescence leads to a higher open circuit voltage through the photon recycling effect, which is critical in radiative limited solar cells. Furthermore, interesting features arise in the experimental external and internal quantum efficiencies (EQE and IQE) for solar cells with such reflective back side reflectors. This includes an increase in EQE magnitude compared to cells on absorptive substrates, and an extension of the IQE edge towards longer wavelengths. The former characteristic is due to an increased photon path length in the active region, which is a consequence of the high reflection occurring in the back side. The latter, however, is not a real feature of the interaction between the light and the solar cell materials, but a consequence of the way the IQE is defined and calculated. The resulting separation of the IQE and EQE near the bandedge of the solar cell thus questions the concurrent definitions for the IQE commonly referred to in the literature, which is clarified in this work. The influence of the definition of quantum efficiency in the material diffusion length extraction is also discussed.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 105-109, Mosaic Solutions AS is developing a novel concept for conductive adhesives for use in electrical interconnection of solar modules. The goal is to provide an alternative to the current soldering process in module manufacturing, enabling lower process temperatures and reducing the amount of toxic elements, e.g. lead. The conductive adhesive is based on replacing solid silver flakes by polymer particles coated with a thin layer of silver. The main advantage of this concept, compared to conventional conductive adhesives, is a typical ten-fold reduction in silver consumption. We have investigated the electrical properties of conductive adhesives based on silver-coated polymer particles, and demonstrated the use of the conductive adhesive concept in module manufacturing. The results are promising, showing that the electrical conductivity is more than sufficient for use in solar modules, and that our conductive adhesive concept represents a promising and realistic alternative to soldering.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 176-179, The increment of the PV market has led to multiple PV installations which operate under non-ideal conditions. Heavy shading is expected in rooftop installations, Building Integrated Photovoltaics and solar powered vehicles. Demand of an increased energy-yield, despite of the non-uniform conditions render reconfigurable topologies a promising solution for such installations. Evaluation of the performance of a PV module can be performed either on the field or in a detailed simulation environment. The problem of the existing solutions is a large cost investment for constructing all potential topologies and the large time requirements for detailed simulation of the entire module. A simulation framework is proposed here which can significantly speed up the evaluation process of different reconfigurable PV module instantiations and conventional modules for different operating scenarios with a high accuracy level.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 165-168, To reduce cell-to-module (CtM) losses for aesthetically appreciated all-black modules we applied a black powder coating with low infrared absorption to standard back foils used in PV modules. Upon the application of such powder coating the IR reflective properties of the underlying substrate are largely preserved. For Cu foil substrates approximately 85% reflection in near-infrared was recorded, while for a white polyamide substrate reflection was 60%. These black, IR reflecting back foils were incorporated in single-cell laminates with n-Pasha bifacial solar cells. From these structures the potential Isc gain from the application of such coatings in PV modules as compared to conventional all-black modules is estimated to be 1.4 – 1.8%.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 138-140, We present the exact analytical solution to minority-carrier transport in a non-uniformly doped Si region and the expression for emitter saturation current density, Jo, for the case, where diffusivity is unaltered by doping and lifetime is only determined by Auger recombination. We call this case "intrinsic transport". Numerical simulations show that, at negligible SRH recombination, assuming intrinsic transport also at doping levels lower than 5×1018 cm-3 in both n- and p-type emitters is reasonable. We apply the previous issues to fit reported data of Jo in both n- and p-type emitters as a function of sheet resistance, RSHEET. To this aim, an analytical expression for Jo(RSHEET) is derived.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 5-10, A new I-V measurement set-up called LaserSim has been developed for photovoltaic laser power converters – photovoltaic cells optimized for monochromatic artificial light - providing irradiances of up to 89 W/cm². The evaluation of the set-up and first I-V curve and efficiency measurements are presented. Similar to flash simulators used for I-V characterization of solar cells, the LaserSim is using transient measurement routines to avoid an influence of heating of the samples during measurement. An excellent light uniformity in the designated test area was realized. A beam sampler allows for in-situ irradiance determination while recording I-V data. This is mandatory for characterization of devices showing a non-linear behavior of short circuit current with irradiance. Efficiency values under monochromatic light at 809 nm have been measured for a single junction GaAs cell (55.6 %) and a dual-junction GaAs device (53.5 %).

32nd European Photovoltaic Solar Energy Conference and Exhibition; 141-147, By comparison of the experimental dependence of bulk lifetime in silicon on the doping and excitation levels with theoretical calculations, it is shown that a new recombination channel becomes operative when Shockley- Read-Hall lifetime is below 20 ms and the density of doping impurities or the excess electron-hole pair density is of the order of 1016 cm-3. This recombination mechanism is related to the non-radiative exciton Auger recombination assisted by the deep impurities in the bulk. The influence of non-radiative exciton recombination on the photoconversion efficiency in solar cells is analyzed. It is shown that the shorter the Shockley-Read-Hall lifetime, SRH, the stronger its effect. In particular, for SRH = 100 μs, this recombination channel leads to the reduction of photoconversion efficiency by 5.5 %, whereas for SRH ≈ 1 μs, the photoconversion efficiency is about twice as small as the value obtained without taking non-radiative exciton recombination into account.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 218-222, In optical power transmission systems photovoltaic cells are used as power converters for monochromatic light. In case of powering remote sensors, supplementary to the optical power link also bidirectional data transmission between the two sides of the optical link is required. It is appealing to integrate the functionalities of the optical power link as well as the data up- and downlink into one. In this work, different concepts on how this integration and combination of functionalities can be realized are explored and possible system and device architectures for integrated transceiver devices are discussed, including different examples of practical realizations based on advanced semiconductor fabrication techniques.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 191-195, The variable nature of solar energy required for its efficient use the complement of energy storage to adapt adequately the generation and production curves. As PV/T technology produces both electricity and heat energy, two storage devices should be necessary. Batteries are the most common method for storing electricity. Nevertheless, different technologies are available to store heat energy. Thermal energy storage can be classified into sensible or latent heat systems, depending if the substance that storages the energy changes its temperature during the process or its physical phase. Phase Change Materials (PCM´s) involve high amount of energy with small changes in volume and temperature so they are promising materials to keep temperature almost constant and store heat energy. In this work a complete study of different types of PCM for its application in PV/T is presented. For this purpose, different materials are classified in terms of its chemical structure and also by its use in PV/T technology. Great number of substances susceptible to be used as PCMs in a heat storage system is showed in the work by an exhaustive bibliography review. Only those PCM´s with melting temperature lower than 70 ºC have been taken in mind for this work. Upper temperatures do not provide enough PV efficient increase

32nd European Photovoltaic Solar Energy Conference and Exhibition; 135-137, Conduction mechanism was investigated from DC and AC conductivity measurements in the bulk ternary semiconductor compound Cu2SnS3 that is prepared by the hydrothermal technique. The complex impedance spectroscopy in the frequency range 100Hz–1MHz and temperature range 300K–475K is used to study the electrical properties of this material. The activation energy for conduction and relaxation mechanisms is estimated. The temperature dependence of relaxation times for grain and grain boundaries contributions are analyzed. From the equivalent circuit that takes into account the distribution of relaxation times, electrical resistance for the grain and grain-boundary are determined and their temperature dependence is analyzed.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 212-217, Highly mismatched alloy of ZnTe:O for intermediate band solar cell application was conventionally prepared by in-situ molecular beam epitaxy alloying, or ion implantation into ZnTe single crystal wafer. In this study, an unique method to realize ZnTe:O intermediate band material was employed, combing ZnTe molecular beam epitaxy and subsequent oxygen ion implantation and final laser pulse ablation. Oxygen band related emissions had been observed from laser pulse annealed ZnTe:O films. Poly-crystalline ZnTe also showed potential for intermediate band solar cell application.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 42-47, We present a novel module design to increase the power output of bifacial modules without compromising the increased energy yield due to the bifaciality. This innovation includes a highly reflective interlayer between and around the bifacial solar cells and laminated between the front and rear encapsulant. Although bifacial solar cells in modules with transparent front and rear sides can absorb light incident at either side, the transmission of (infrared) light through the rear side reduces the Pmax. The lower Wp rating is seen as a drawback for bifacial modules. The innovative white bifacial modules show almost the same front side Isc and Pmax as a monofacial module and a 2.2% higher Pmax, due to increased Isc, compared to transparent bifacial modules. The same increase is found for the rear side Pmax. The bifacial energy yield for white bifacial modules, due to the higher Pmax for both sides, is much higher than the slightly higher ground reflected “albedo” light of regular bifacial modules.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 127-130, It is well known that high temperatures affect in a negative way the performance of PV Silicon modules. There are several ways of decreasing the modules temperature by external cooling, therefore increasing its performance: water and air cooling. Although we are interested in studying the way that the PV module transfers heat to the external cool water while it approaches its optimum working temperature, this work is a first step towards developing the digital tools to study water cooling of PV roof installations. The model, which is a fine modeling, studies the cooling of a PV panel by air in two different cases of convection: natural cooling in a cool environment and forced cooling with wind. The numerical simulations show the efficient heat transfer between the PV panel (modeled by a glass plate) and ambient air. We use the Navier-Stokes equations coupled with the heat equation, using the Boussinesq approximation to take into account the thermal variation of density. This allows us to take into account the varying parameters as temperature, wind speed and inclination of panel (gravity). The simulations show that the most efficient regime for free convection is when the module is not perpendicular to gravity direction. The efficiency increases with the wind speed. The most efficient case is obtained when the wind is parallel to the panel.

32nd European Photovoltaic Solar Energy Conference and Exhibition; 232-236, In this work we investigated the influence of fabrication procedure of indium tin oxide (ITO) seed layers, acting as front contacts in silicon heterojunction solar cells, on the growth of ZnO antireflective layers. Furthermore, ZnO nanorod growth out of ZnCl2 and Zn(NO3)2 solution was compared. It was observed that for both ZnCl2 and Zn(NO3)2 nanorod layers, the ITO sheet resistance affects the density and size of resulting nanorods. The most effective antireflective nanorod layers grew on an ITO layer with a sheet resistance of approximately 50 Ω. In this case, the nanorod layers had a suitable density, which was neither too low nor too high. The application of such a nanorod antireflective layer in a SHJ solar cell led to a relative gain in the short circuit current density by 0.6 %.