• Energy Research

In this work, we investigated the morphology, electrical conductivity, catalytic properties, and binding energies of electronic states of a system consisting of acetylene carbon black (AB) and graphite as efficient and low-cost counter electrodes (CEs) for dye-sensitized solar cells (DSSCs), where ratios of AB to graphite of 0:1, 1:3, 1:1, 3:1, and 1:0 were investigated. These carbon-based CEs were characterized using four-point probe conductivity measurement, field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NAXAFS), electrochemical impedance spectrum (EIS), and current-voltage (I-V) performance. Introduction of small AB particles into graphite paste enhanced the electronic conductivity of AB-graphite composite due to the bridging of the graphite flakes for electrocatalytic activity of triiodide reduction. AB particles also offer large surface area to provide high electrochemical performance in DSSCs. The overall highest power conversion efficiency of 5.06% was achieved for the DSSC fabricated with a CE consisting of AB-graphite ratio of 3:1, which is comparable to the DSSC performance with conventional platinum (Pt) CE. These findings suggest that AB and graphite composite could be a promising CE for low-cost DSSCs.

Abstract This work describes the efficient improvement of dye-sensitized solar cells (DSSC) utilizing a photoanode with a plasmonic sandwiched silicon dioxide/silver/titanium dioxide (SiO2/Ag/TiO2) structure and a counter electrode (CE) of polypyrrole/reduced graphene oxide/indium tin oxide (Ppy/rGO/ITO) assembled with an aluminium (Al) foil as a reflective layer. The localized surface plasmonic resonance induced from Ag increases the absorption of the dye molecules, and hence significantly improves the electron collection and light-harvesting efficiencies. Compared with conventional photoanode of DCCSs composed of TiO2 paste, the photovoltaic cells containing the plasmonic sandwiched structure exhibits a remarkable improvement in the power conversion efficiency (ƞ), with up to a 2-fold enhancement (from 0.6% to 1.2%), along with a 68.37% increment in the short-circuit current density (Jsc), from 2.15 to 3.62 mA cm−2. The reflective layer of Al foil contributes to a significant enhancement of ƞ of 1.7-fold for the DSSC.

Abstract Silicon nanostructures were grown by a chemical vapor deposition (CVD) technique, using different silica masses, and their photoelectrochemical characteristics were investigated. These nanostructures were found mainly to have two kinds of structures; nanorods and nanowires. Si nanorods with an average diameter of about 250 ​± ​50 ​nm were prepared at silica mass of 15 ​mg. An increase in silica to 100 ​mg results in a high density of Si nanowires with a relatively smaller in average diameter of 30 ​± ​4 ​nm. Moreover, the band gap energies of the Si nanowires and nanorods are between 1.8 and 1.9 ​eV showing visible light absorption capability. The as-grown Si nanowires have a better photocurrent density of 0.5 ​mA ​cm-2 as compared to as-grown Si nanorods, at a potential of 0 ​V in Ag/AgCl aqueous solution. This possibly due to the extremely large surface area and large number of active sites of Si nanowires, which could result in enhancing the water splitting oxidation and reduction processes. The role of silica in the growth mechanism was also discussed.

Une couche de SnO2 sur mesure utilisant des couches de transport d'électrons doubles (ETL) a été conçue pour surmonter les barrières énergétiques interfaciales, améliorer le transport de charge et diminuer la recombinaison de charge aux interfaces pérovskite/ETL. Grâce à cette double approche d'ingénierie interfaciale, des couches compactes de SnO2 avec un alignement idéal du niveau d'énergie interfaciale ont été préparées à l'aide de sels de SnCl2 et de NH4Cl, conduisant à une extraction de charge efficace. Des cellules solaires stables en pérovskite avec un rendement de conversion d'énergie de 21,46 %, une tension élevée en circuit ouvert de 1,10 V et un facteur de remplissage de 0,79 ont été obtenues avec succès grâce à cette approche. Les dispositifs présentaient également une hystérésis négligeable et aucune perte d'efficacité significative après un test de stabilité de 2400 h dans des conditions ambiantes sans encapsulation. Ces résultats démontrent une approche efficace pour obtenir des couches ETL de haute qualité pour des cellules solaires efficaces et stables. Se diseñó una capa de SnO2 personalizada que utiliza capas de transporte de electrones dobles (ETL) para superar las barreras de energía interfaciales, mejorar el transporte de cargas y disminuir la recombinación de cargas en las interfaces perovskita/ETL. A través de este enfoque de ingeniería interfacial dual, se prepararon capas compactas de SnO2 con una alineación ideal del nivel de energía interfacial utilizando sales de SnCl2 y NH4Cl, lo que condujo a una extracción de carga eficiente. Las células solares de perovskita estables con una eficiencia de conversión de energía del 21.46%, un alto voltaje de circuito abierto de 1.10 V y un factor de llenado de 0.79 se lograron con éxito utilizando este enfoque. Los dispositivos también exhibieron una histéresis insignificante y ninguna pérdida significativa de eficiencia después de una prueba de estabilidad de 2400 h en condiciones ambientales sin encapsulación. Estos resultados demuestran un enfoque eficiente para lograr capas ETL de alta calidad para células solares eficientes y estables. A tailored SnO2 layer using double electron transport layers (ETLs) was designed to overcome interfacial energy barriers, enhance charge transport, and decrease charge recombination at the perovskite/ETL interfaces. Through this dual interfacial engineering approach, compact SnO2 layers with an ideal interfacial energy-level alignment were prepared using SnCl2 and NH4Cl salts, leading to efficient charge extraction. Stable perovskite solar cells with a power conversion efficiency of 21.46%, a high open-circuit voltage of 1.10 V, and a fill factor of 0.79 were successfully achieved using this approach. The devices also exhibited negligible hysteresis and no significant efficiency loss after a 2400 h stability test at ambient conditions without encapsulation. These results demonstrate an efficient approach to achieving high-quality ETL layers for efficient and stable solar cells. تم تصميم طبقة SnO2 المصممة خصيصًا باستخدام طبقات نقل الإلكترون المزدوجة (ETLs) للتغلب على حواجز الطاقة البينية، وتعزيز نقل الشحنة، وتقليل إعادة تركيب الشحنة في واجهات البيروفسكايت/ETL. من خلال هذا النهج الهندسي البيني المزدوج، تم إعداد طبقات SnO2 المدمجة مع محاذاة مثالية لمستوى الطاقة البينية باستخدام أملاح SnCl2 و NH4Cl، مما أدى إلى استخراج شحن فعال. تم تحقيق خلايا بيروفسكايت الشمسية المستقرة بكفاءة تحويل طاقة تبلغ 21.46 ٪، وجهد دائرة مفتوحة عالية يبلغ 1.10 فولت، وعامل تعبئة يبلغ 0.79 بنجاح باستخدام هذا النهج. أظهرت الأجهزة أيضًا تباطؤًا طفيفًا وعدم وجود خسارة كبيرة في الكفاءة بعد اختبار الثبات لمدة 2400 ساعة في الظروف المحيطة دون تغليف. تُظهر هذه النتائج نهجًا فعالًا لتحقيق طبقات ETL عالية الجودة للخلايا الشمسية الفعالة والمستقرة.

Mixed Pb/Sn halide perovskites have shown wide band gap tunability, allowing these materials to become practical components. Nevertheless, a high density of Sn vacancies and an undesirable oxidation of Sn­(II) to Sn­(IV), even in the absence of any oxidant species, diminish film performance and air-stability due to recombination losses of charge carriers. More recently, A-site substitution by several organic halide compounds as additives has been engaged to improve film stability through dangling bond passivation. However, exploring the roles of passivation via A-site doping in Pb/Sn perovskites requires a more insightful investigation. Here, we explicate the structural design of 2D perovskite formation on the 2D/3D mixed Pb/Sn perovskite layer and its effects on electronic properties and stability. Surprisingly, we observe that PEAI treatment causes 2D perovskite formation at the interface of the layered perovskite. In situ growth of the 2D perovskite significantly suppresses Sn and I vacancies via Lewis base passivation. With the control of the conversion process, the interfacial 2D establishes on top of the layered perovskite, resulting in valence-band maximum down-shifting, which in turn adjusts the energy level. Remarkably, the crystallinity along with the more preferred (100) orientation is significantly improved by the PEAI treatment. The phase stability under ambient conditions is enhanced as a result of the 2D passivation. Through various characterization methods, the deep investigation of 2D perovskite interfacial formation was carefully engaged, yielding insights highly beneficial for various optoelectronic applications.

In this article, we present the data collected from the fabricated carbon black-graphite counter electrode for dye-sensitized solar cells (DSSC) by incorporating binders such as titanium (IV) isopropoxide (TTIP), and zirconium (IV) dioxide (ZrO2). The addition of binders to the carbon black-graphite composite (CB/Gr) can drastically improve the adherence between the counter electrodes and the fluorine-doped tin oxide (FTO) substrate, surface area and the interparticle connection between the carbon materials. These data are presented which comprise of the resistivity measurements, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX), and near-edge X-ray absorption fine structure (NEXAFS). The collection of this data was performed at room temperature. Detailed analysis of the data can be found in [1].

Abstract In this work, we investigate how Al and Mg doped mesoporous TiO2 layers can improve the power conversion efficiency (PCE) of perovskite solar cells (PSCs) with respect to undoped mesoporous TiO2. The PSC configuration used in this study consists of mesoscopic structure with CH3NH3PbI3 as the perovskite absorber. A PSC with optimized mol% of Al and Mg doped mesoporous TiO2 layers has been shown to achieve up to 22% higher efficiency than that of pure TiO2. While the Mg doping only enhances the open-circuit voltage (VOC), the Al doping effectively enhances the VOC, the short-circuit current density (JSC), and the fill factor (FF). The occupancy of the doped metals in the lattice is confirmed by XRD, EDX, and XPS. The Mg doping increases the band gap of TiO2 while the Al doping decreases it. The wide band gap in Mg doped TiO2 reduces the electron and hole recombination rate, thus increasing the JSC and VOC. By Al doping, deep trap sites in the TiO2 are eliminated, and this effectively reduces the recombination losses and in turn, increases the JSC. The enhanced electron-hole generation rate attributed to the decrease in the band gap of Al doped TiO2 also increases the JSC. In addition, there is an enhancement on the electron mobility by the presence of Al metal and this gives an increase in the FF. The results have demonstrated the possibility of improving the PCE of PSCs by fine tuning the band gap of mesoporous TiO2.

Abstract In this work, we have investigated the performance of acetylene carbon black/graphite (AB/G) composite counter electrodes (CEs) by incorporating TiO2 as a binder in dye-sensitized solar cells (DSSCs). We obtained five types of composite CE films at different weight ratios of 0:1, 1:3, 1:1, 3:1 and 1:0 by adding a constant amount of TiO2 to a mixture of AB/G. The performance of the composite electrodes was assessed by using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, electrochemical impedance spectroscopies and photocurrent density–voltage characteristics. The results have shown enhanced DSSC efficiency due to improved charge transfer properties of the CE when adding TiO2. TiO2 enhances the binding of the electrode to the substrate. AB/G/TiO2 composites show superior overall results compared to AB/TiO2 and G/TiO2. Since AB has high catalytic activity and surface area, as the AB content of the composite is increased, the electrochemical properties of the CEs are improved. The DSSC with AB:G (3:1) exhibited the maximum power conversion efficiency (PCE) of 5.9% with the highest fill factor (FF) of 0.55, which are comparable to those DSSCs employing platinum CEs with PCE of 6.2% and FF of 0.67.