Combined Optical-Electrical Optimization of Cd1−xZnxTe/Silicon Tandem Solar Cells

Although the fundamental limits have been established for the single junction solar cells, tandem configurations are one of the promising approaches to surpass these limits. One of the candidates for the top cell absorber is CdTe, as the CdTe photovoltaic technology has significant advantages: stability, high performance, and relatively inexpensive. In addition, it is possible to tune the CdTe bandgap by introducing, for example, Zn into the composition, forming Cd1−xZnxTe alloys, which can fulfill the Shockley–Queisser limit design criteria for tandem devices. The interdigitated back contact (IBC) silicon solar cells presented record high efficiencies recently, making them an attractive candidate for the rear cell. In this work, we present a combined optical and electrical optimization of Cd1−xZnxTe/IBC Si tandem configurations. Optical and electrical loss mechanisms are addressed, and individual layers are optimized. Alternative electron transport layers and transparent conductive electrodes are discussed for maximizing the top cell and tandem efficiency

Optical and electrical design guidelines for ZnO/CdS nanorod-based CdTe solar cells

An alternative structure to planar CdTe solar cells is realized by coating ZnO/CdS nanorods (NRs) with a CdTe layer. These structures are expected to achieve high-powered conversion efficiencies through enhanced light absorption and charge carrier collection. ZnO NR-based CdTe solar cell efficiencies; however, they have remained well below their planar counterparts, thus hindering NRs in CdTe solar cells' advantages. Here, we analyze the light trapping and carrier collection efficiencies in two types of ZnO NR-based CdTe solar cells through optical and electrical simulations. The buried CdTe solar cells are formed by completely filling the gaps in between ZnO/CdS NRs. This produces a maximum achievable photo-current of 27.4 mA/cm(2) when 2000 nm-tall and 20 degrees-angularly-deviated NRs are used. A short-circuit current density of 27.3 mA/cm(2) is achievable with the same geometry for 5 rods/mu m(2)-dense NRs when a moderate CdTe doping density and a CdS/CdTe surface velocity of 10(16) cm(-3) and 10(4) cm/s are used, respectively. We reveal the potential of buried CdTe solar cell for high-charge carrier collection and provide a design guideline in order to achieve high short-circuit current densities with ZnO NR-based CdTe solar cells. (c) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Guideline for Optical Optimization of Planar Perovskite Solar Cells

Organometallic halide perovskite solar cells have emerged as a versatile photovoltaic technology with soaring efficiencies. Planar configuration in particular, has been a structure of choice thanks to its lower temperature processing, compatibility with tandem solar cells and potential in commercialization. Despite all the breakthroughs in the field, the optical mechanisms leading to highly efficient perovskite solar cells lack profound insight. In this paper, a comprehensive guideline is introduced involving semi-analytical equations for thickness optimization of the front and rear transport layers, perovskite, and transparent conductive oxides to improve the antireflection and light trapping properties, and therefore to maximize the photocurrent of perovskite solar cells. It is shown that a photocurrent enhancement above 2 mA/cm2 can be achieved by altering - reducing or increasing - the thicknesses of the layers constituting a CH3NH3PbI3 (MAPI) type perovskite solar cell. The proposed guideline is tested against experiments as well as previously published experimental and simulation results for MAPI. Additionally, the provided guideline for various types of perovskites can be extended to other direct band gap absorber-based solar cells in superstrate configuration

Enhanced Light Emission from Erbium Doped Silicon Nitride in Plasmonic Metal-Insulator-Metal Structures

Plasmonic gratings and nano-particle arrays in a metal-insulator-metal structures are fabricated on an erbium doped silicon nitride layer. This material system enables simple fabrication of the structure, since the active nitride layer can be directly grown on metal. Enhancement of collected emission of up to 12 is observed on resonance, while broad off-resonant enhancement is also present. The output polarization behavior of the gratings and nano-particle arrays is investigated and matched to plasmonic resonances, and the behavior of coupled modes as a function of inter-particle distance is also discussed.Comment: 9 pages, 6 figures updated because pdf was still non-functiona

Coupled fiber taper extraction of 1.53 um photoluminescence from erbium doped silicon nitride photonic crystal cavities

Optical fiber tapers are used to collect photoluminescence emission at ~1.5 um from photonic crystal cavities fabricated in erbium doped silicon nitride on silicon. Photoluminescence collection via fiber taper is enhanced 2.5 times relative to free space, with a total taper collection efficiency of 53%. By varying the fiber taper offset from the cavity, a broad tuning range of coupling strength is obtained. This material system combined with fiber taper collection is promising for building on-chip optical amplifiers.Comment: 10 pages, 7 figure

Preparation and Characterization of Mixed Halide MAPbI3−xClx Perovskite Thin Films by Three‐Source Vacuum Deposition

Chloride has been extensively used in the preparation of metal halide perovskites such as methylammonium lead iodide (MAPbI3-xClx), but its persistence and role in solution-processed materials has not yet been rationalized. Multiple-source vacuum deposition of perovskites enables a fine control over the thin-film stoichiometry, and allows to incorporate chemical species irrespectively of their solubility. In this communication, we present the first example of mixed MAPbI3-xClx thin films prepared by three-source vacuum deposition using MAI, PbI2 and PbCl2 as precursors. The optoelectronic properties of the material are evaluated through photovoltaic and electro-/photo-luminescent characterizations. Besides the very similar structural and optical properties of MAPbI3 and MAPbI3-xClx, we observed an increased electroluminescence efficiency, longer photoluminescence lifetimes, as well as larger photovoltage in the presence of chloride, suggesting a reduction of the non-radiative charge recombination

Thermal conductivity and photoluminescence of light-emitting silicon nitride films

Silicon-rich and rare-earth-doped nitride materials are promising candidates for silicon-compatible photonic sources. This work investigates the thermal conductivity and photoluminescence (PL) of light emitting samples fabricated with a range of excess silicon concentrations and annealing temperatures using time-domain picosecond thermoreflectance and time-resolved photoluminescence. A direct correlation between the thermal conductivity and photoluminescence dynamics is demonstrated, as well as a significant reduction of thermal conductivity upon incorporation of erbium ions. These findings highlight the role of annealing and stoichiometry control in the optimization of light emitting microstructures suitable for the demonstration of efficient Si-compatible light sources based on the silicon nitride platform. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3682508

Hybrid Vapor-Solution Sequentially Deposited Mixed-Halide Perovskite Solar Cells

The recent sky-rocketing performance of perovskite solar cells has triggered a strong interest in further upgrading the fabrication techniques to meet the scalability requirements of the photovoltaic industry. The integration of vapor-deposition into the solution process in a sequential fashion can boost the uniformity and reproducibility of the perovskite solar cells. Besides, mixed-halide perovskites have exhibited outstanding crystallinity as well as higher stability compared with iodide-only perovskite. An extensive study was carried out to identify a reproducible process leading to highly crystalline perovskite films that when integrated into solar cells exhibited high power conversion efficiency (max. 19.8%). This was achieved by optimizing the deposition rate of the PbI2 layer as well as by inserting small amounts of methylammonium (MA) bromide and chloride salts to the primary MAI salt in the solution-based conversion step. The optimum MABr/MAI molar ratio leading to the most efficient and stable solar cells was found to be 0.4. Stabilities were in excess of 90 hours for p-i-n type solar cells. This reproducible approach towards the fabrication of triple halide perovskites using a hybrid vapor-solution method is a promising method towards scalable production techniques

İnce Film Silisyum Güneş Hücrelerinde Işık Yönetimi

Günümüz fotovoltaikteknolojisinde kullanılan yüksek verimliliğe sahip tek kristal silisyum (k-Si) güneş hücrelerinin kalınlığı yaklaşık 180 mikrondur ve Si pulunun maliyeti güneş modülün toplam maliyetinin yaklaşık olarak üçte birine tekabül etmektedir. Gelecekte Si pul kesme teknolojisi kullanılarak 120 mikron kalınlığında Si pullarının üretileceğini öngörülmektedir. Ancak Si kalınlığındaki bu sınırlı azalmanın maliyet/verimlilik oranına etkisi de çok sınırlı kalacaktır. İnce film (~10-40 mikron) k-Si pullarından üretilen yüksek verimlilikteki güneş hücreleri Si hücre maliyetini azaltılabilir. Tek kristal ince film Si güneş hücrelerinin üretilebilmesi için üç temel zorluk vardır. Bunlar silisyumun kütükten sıyrılması, güneş hücresinin üretim değişkenlerinin ince film Si güneş hücreleri için optimizasyonu, ve ince film Si güneş hücreleri için uygun ışık kapanı yapılarının geliştirilmesidir.Silisyum dolaylı bant yapısını nedeniyle zayıf bir ışık soğurucudur. 20 m kalınlığındaki bir silisyumun 800 nm ve üzerindeki dalga boylarındaki fotonları verimli bir şekilde soğurması için ışık kapanına ihtiyacı vardır. Günümüz teknolojisi kalın Si güneş hücrelerinde ışığın Si içerisinde soğurmasını artırmak için yüzeyde boyutları 3-10 m mertebesinde olan rastgele piramitler oluşturulur. Ancak bu yapılar ince Si güneş hücreleri için çok büyük olduklarından uygun değildirler. Bu sunumda, ince film k-Si güneş hücreleri için geliştirdiğimiz ışık kapanı yapılarından örnekler sunulacaktır. Kalınlıkları 8 –30 mikron ve verimleri 9,6 –15,7 % arasında değişen farklı ışık kapanı yapılarına sahip k-Si güneş hücrelerinin performansları tartışılacaktır. Bu sonuçlar uygun ışık kapanı kullanılan ince film kristal silisyumun esnek, hafif ve verimli güneş hücre üretimi için uygun bir malzeme olduğunu göstermektedir