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The parasitic shunt resistance, bias dependence of the photocurrent and phenomena causing a second exponential term in the current density (J)-voltage (V) equation reduce the open circuit voltage, Voc, of illuminated solar cells below the ideal value predicted by the J-V equation having only a single exponential term. This study reports an approximate closed-from solution of the transcendental Voc equation which directly reflects these losses. The solution estimates Voc as a weighted parallel combination of the limiting Voc values corresponding to the domination of one of the several terms of the Voc equation. The solution allows quick design calculation of the Voc of a wide variety of cells in terms of all physical parameters, and provides insight into the influence of losses owing to various factors. � 2012 The Institution of Engineering and Technology.

Two new soluble alternating alkyl-substituted benzo[1,2-b:4,5-b′] dithiophene and ketone-substituted thieno[3,4-b]thiophene copolymers were synthesized and characterized. We found that grafting 3-butyloctyl side chains to the benzo[1,2-b:4,5-b′]dithiophene unit at C4 and C8 afforded the resulting polymer (P1) a high hole mobility (∼10-2 cm2 Vs-1) and a low-lying HOMO energy level (5.22 eV). Preliminary experiments in bulk heterojunction solar cells using P1 as the electron donor demonstrated a high power conversion efficiency of 4.8% even with PC 61BM as the electron acceptor. The introduction of an electron-withdrawing fluorine atom into the thieno[3,4-b]thiophene unit at the C3 position (P2) lowers the HOMO energy level and consequently improves the open circuit voltage from 0.78 to 0.86 V. These values are about 0.1 V higher than those reported for their analogues based on alkoxy-substituted benzo[1,2-b:4,5-b′]dithiophene. This work demonstrates that the replacement of the alkoxy chains on the benzo[1,2-b:4,5-b′]dithiophene unit with less electron-donating alkyl chains is able to lower the HOMO energy levels of this class of polymers without increasing their band gap energy. © 2011 The Royal Society of Chemistry.

Micromachined thermopiles are considered as a cost-effective solution for energy harvesters working at a small temperature difference and weak heat flows typical for, e.g., the human body. They can be used for powering autonomous wireless sensor nodes in a body area network. In this paper, a micromachined thermoelectric energy harvester with 6 μm high polycrystalline silicon germanium (poly-SiGe) thermocouples fabricated on a 6 inch wafer is presented. An open circuit voltage of 1.49 V and an output power of 0.4 μW can be generated with 3.5 K temperature difference in a model of a wearable micromachined energy harvester of the discussed design, which has a die size of 1.0 mm × 2.5 mm inside a watch-size generator. © 2010 IOP Publishing Ltd.

Les couches minces semiconductrices de CuInS2 sont préparées par la technique de pulvérisation réactive et sans air (P.S.A.), avec différents rapports de concentrations Cu/In en solution variant de 0,8 à 1,3. Nous avons constaté par analyse aux rayons X qu'un excès d'indium engendre l'apparition de phases indésirables telles que In2S3 et In 6S7. Pour un rapport Cu/In supérieur ou égal à 1, avec une concentration d'indium de 3 × 10^-2 M, ces phases disparaissent. L'obtention des couches de CuInS2 proche de la stœchiométrie (Cu/In en couche égal à 1) nécessite un rapport Cu/In en solution égal à 1,1. Pour cette valeur, les dépôts sont bien cristallisés et orientés préférentiellement suivant la direction (112). D'autre part l'étude des caractéristiques intensité-potentiel des cellules CdS/CuInS2, formées par adjonction du sulfure de cadmium à ce type de couches, montre que leurs performances sont étroitement liées à la composition chimique et l'épaisseur de l'absorbeur CuInS 2. Pour une épaisseur de 0,5 μm, nous avons constaté que le processus de transport est gouverné par le processus de génération-recombinaison (facteur d'idéalité A < 2) lorsque le rapport Cu/In est égal à 1,1. Les caractéristiques photovoltaïques sont relativement améliorées pour une épaisseur optimale de 1 μm. En particulier le facteur A et le courant de fuite Is ont diminué respectivement de 1,98 à 1,46 et de 4,28 μA à 0,34 μA suite à une diminution des défauts de structure, agissant en tant que centres de recombinaison dans le matériau. Dans ces conditions, la tension de circuit ouvert Vco est de 350 mV, le courant de court-circuit Icc est de 4,6 mA.cm-2 et le rendement η est de l'ordre de 1 % (P = 100 mW.cm-2).

In the superionic conducting quarternary system Agl-Ag2O-V2O5-P2O5, the best ionic conductivity was obtained for the composition 66.6% Agl-33.3% (2Ag2O-1 (V2O5-P2O5)), when the GF/GM ratio was varied from 0.20 to 5.0. Then fixing the GF/GM ratio at 0.50, the ratio of the glass formers V2O5 and P2O5 were varied and the highest conducting composition was obtained as 66.6% Agl-22.2 Ag2O-11.1% (0.8 V2O5-0.2 P2O5). A preliminary investigation using this material in the form of an electrolyte in a solid state electrochemical cell is reported. The polycrystalline and amorphous compounds were prepared from the same melt, by open air crucible melting and the rapid quenching technique. The ionic conductivity for the best conducting polycrystalline (hence referred as 66VP82P) and amorphous (66VP82G) samples was obtained as 8.3 ? 10-3 and 4.2 ? 10-2 �-1 cm-1 respectively. The electronic conductivity of the order 10-10 �-1 cm-1 was observed for 66VP82G and 10-8 �-1 cm-1 for 66VP82P samples. Thermoelectric power studies revealed that the charge carriers are the Ag+ ions, with an activation energy of 0.288eV for 66VP82G, which correlated well with the activation energy obtained from the conductivity measurements. The dielectric constant, dielectric loss and the loss tangent were calculated for both polycrystalline and glassy 66VP82 material. It was observed that the dielectric loss is more for the glassy material than the polycrystalline material. Solid state galvanic cells with 66.6% Agl-22.2% Ag2O-11.1% V2O5, 66.6% Agl-22.2%-Ag2O-11.1% P2O5 and 66.6% Agl-22.2% Ag2O-11.1% (0.8 V2O5-0.2 P2O5) (coded as 66V, 66P and 66VP82 respectively) electrolytes were constructed. Both polycrystalline and amorphous electrolyte cells were fabricated for a comparative study and the polarization effects were observed to be negligible in amorphous cells. The variation of open circuit voltage with temperature was reported and the current discharge curves indicate that the 66VP82 material has higher current capacity with high current drain when compared to 66V and 66P cells. ? 1988 Chapman and Hall Ltd.

Cet article présente les résultats d'une étude exploratoire de la passivation par l'hydrogène des défauts recombinants dans les rubans de silicium polycristallin élaborés par la méthode RAD. L'incorporation d'hydrogène a été effectuée sur des photopiles nues au moyen d'une source d'ions du type Kaufman. On montre que les caractéristiques globales des photopiles — photocourant, tension de circuit ouvert et facteur de forme — sont considérablement améliorées tandis que leurs distributions sont resserrées. Ces améliorations sont reliées à la réduction de la vitesse de recombinaison des porteurs minoritaires sur les interfaces du type joints de grains ou de mâcles et surtout, à l'augmentation de la longueur de diffusion dans les parties homogènes ; ce dernier effet est associé à une réduction importante de l'activité des centres pièges. Ainsi, le rendement de conversion, sous éclairement AM1, des photopiles RAD « passivées » à l'hydrogène peut être relativement élevé : la meilleure photopile ainsi traitée présente un rendement de 15,5 % (surface active, 3 cm 2).

Schottky barriers on N-type cadmium telluride have been studied in view of application to solar cells. The barrier heights, as determined by the photoresponse and forward current measurements show a linear dependence upon the metal work function. Barrier heights up to 0.90 eV have been reached for Pt-CdTe contacts. Open circuit voltages up to 680 mV have been measured for such cells. Investigation of the Au-CdTe barrier immediately after the deposition of the metal (no contact with air) has shown that the barrier is formed immediately under vacuum. However, when the device is brought in contact with air, the open circuit voltage increases due to an increase of the n factor.

The open-circuit voltage of organic solar cells from 605 to 858 mV based on subphthalocyanines and C 60 by adding a hole transporting layer e.g., poly (3,4-ethylenedioxy-thiophene), poly(styrenesulfonate) between the anode and SubPc. Meanwhile, the fill factor and short-circuit current were also optimized resulting in a grate enhancement in power conversion efficiency from 0.65% to 1.4%. Based on the optical transfer matrix theory and resistance study at short-circuit conditions R Jsc , the influences of build-in potential, hole injecting barrier on photovoltaic properties have been discussed.

On réalise des photopiles en couches minces en déposant sur une feuille de molybdène du tellurure de cadmium (n), par réaction en phase vapeur des constituants. La région (p) est obtenue par évaporation sous vide de tellurure de cuivre, le contact étant assuré par une grille d'or évaporé. On a mesuré les principales caractéristiques de ces cellules. Pour un éclairement de 50 mW/cm2, on obtient un courant de court-circuit de 7 mA/cm 2, une tension à vide de 400 à 500 mV et un rendement énergétique de 3 %.

We report on ion-implanted, inkjet patterned back junction back contact silicon solar cells with POLysilicon on Oxide (POLO) junctions for both polarities – n+ doped BSF and p+ doped emitter. The recombination behavior is investigated at two different processing stages: before and after trench separation of p+ and n+ regions within polysilicon (poly-Si). Before trench separation, we find a systematic dependence of the recombination behavior on the BSF index, i.e. the p+n+-junction meander length in the poly-Si. Obviously, recombination at the p+n+-junction in the poly-Si limits the implied open circuit voltage Voc,impl. at one sun illumination and the implied pseudo fill factor pFFimpl. to 695 mV and 80%, respectively. After trench isolation, however, Voc,impl (pFFimpl.) values increase up to 730 mV (85.5%), corresponding to a pseudo-efficiency of 26.2% for an assumed short circuit current density Jsc of 42 mA/cm2. We demonstrate a photolithography-free back junction back contacted solar cell with p-type and n-type POLO junctions with an in-house measured champion efficiency of 23.9% on a designated area of 3.97 cm2. This efficiency is mainly limited by the imperfect passivation in the undoped trench regions and at the undoped front side.

The open-circuit voltage developed across a Schottky-Barrier (SB) solar cell was theoretically modeled to estimate it under high level injection conditions. An Open-circuit voltage (Voc) of 0.709 V was obtained for specific metal/n-Si SB solar cell. A substantial increase of 42.6 % in Voc was noticed while comparing our result with that previously calculated in low level injection conditions. Four different metals suitable for making Schottky contact with n-Si were investigated and calculated the variation of Voc with different values of doping concentrations in the semiconductor. The effect of surface recombination velocities (SRV) of charge carriers on Voc was also estimated at such high level injections. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/27897

Engineering the surface at the rear interface between the perovskite and the hole transporting material is of paramount importance to minimize non-radiative losses. We report the use of N-bromosuccinimide (NBS), as an interfacial alleviator to influence crystallization of the perovskite and defect passivation. The NBS treatment promotes added charge extraction and yields devices with improved photovoltaic performance. Thus formed perovskite layers exhibit grain size increment and lowered trap density. An improved device performance was noted with an optimized concentration of 0.5% NBS as compared to pristine perovskite due to the open circuit voltage and short circuit current density enhancement. The coordination of bromide influences the crystal lattice as shown by polarization modulated-infrared reflection-absorption spectroscopy, which in turn may influence charge transport and interfacial properties.

One of the common phenomenona for most of the battery cell chemistries is hysteresis. Since an open circuit voltage (OCV) path is not identical for the charge and discharge of the battery cell at different states of charge (SoC) level, the battery cells show the hysteresis effect. Usually, the OCV i.e. voltage with zero current after previous charge is higher than the OCV after discharge at the same SoC level. It embodies the hysteresis of the battery cell. The OCV is principally subjected to previous operating condition and cannot be taken as self-regulating from the operating history. Therefore, an accurate knowledge of the hysteresis of OCV is vital for various applications and battery models. This is because currently Battery Management Systems (BMS) use the well-defined OCV-SoC representative curve for SoC estimation and power prediction. Particularly lithium-ion batteries with iron-phosphate cathode material show a complex OCV behaviour including a hysteresis that is dependent on the previous operation i.e. the previous state-- charging or discharging. Different cell chemistries exhibit diverse level of the drawbacks because of hysteresis. Those are more prone to catastrophes due to failures to estimate the correct SoC or energy content of the battery consequently limiting operation life of the battery pack. Therefore, novel and more cutting-edge hysteresis management strategies are required to be able to prevent securely the energy storage system from ever facing these critical circumstances. In case of the exchanging between the charging and discharging curves (due to exposure of charge and discharge pulse) makes the SoC estimation problematic since switching from the OCV leads to sudden changes in the output of SoC that physically is not rational for a battery cell. In this chapter, the characteristics of OCV in function of relaxation times (up to 24 hours) for different Li-ion chemistries, temperatures and C-rates (Charge discharge rates) are presented. Moreover, a novel hysteresis compensation structure is introduced based on Kalman filter and statistical error function. These combinations are able to meet the high requirements of estimating accurate SoC using open circuit voltage. In addition, the issues of safety and reliability are going to be increased for the integration of the newly established compensation scheme for the hysteresis phenomenon. A hysteresis compensation framework is deliberated in the sections of this chapter.

We report on two different approaches to fabricate interdigitated back contact silicon heterojunction solar cells without using indium tin oxide (ITO). The standard ITO/Ag backend is either modified by replacing ITO with aluminum-doped zinc oxide (AZO) or completely replaced by a sole aluminum (Al) layer. The very transparent AZO enhances the optical properties at the rear side resulting in an increase in short-circuit current density. The efficiency of the AZO cells remains on the level of the ITO ones, as the fill factor drops slightly. On the contrary, the contact resistivity of annealed Al, in comparison to ITO and AZO, to the emitter and BSF layers is much lower, thus the fill factor is increased. Despite lower open circuit voltages, cells with Al achieve efficiencies of up 22 %, a gain of 0.5 %abs compared to the ITO reference.

Engineering the surface at the rear interface between the perovskite and the hole transporting material is of paramount importance to minimize non-radiative losses. We report the use of N-bromosuccinimide (NBS), as an interfacial alleviator to influence crystallization of the perovskite and defect passivation. The NBS treatment promotes added charge extraction and yields devices with improved photovoltaic performance. Thus formed perovskite layers exhibit grain size increment and lowered trap density. An improved device performance was noted with an optimized concentration of 0.5% NBS as compared to pristine perovskite due to the open circuit voltage and short circuit current density enhancement. The coordination of bromide influences the crystal lattice as shown by polarization modulated-infrared reflection-absorption spectroscopy, which in turn may influence charge transport and interfacial properties.