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ZnO Kaplama Miktarının n-ZnO/p-Si H eteroeklem Güneş Hücresinin Verimliliğine EtkisiÖzet Bu çalışmada, n-tipi çinko oksit/p-tipi silisyum (n-ZnO/p-Si) heteroeklem güneş hücresinin verimliliği üzerinde çinko oksit (ZnO) kaplama miktarının etkisi incelendi. ZnO nanoparçacıklar sol-jel yöntemi ile sentezlendi. Sentezlenen nanoparçacıklar, döndürerek kaplama metodu kullanılarak cam alttaşlar ve p-Si alttaşlar üzerine kaplandı. Kaplama işlemi, 2, 4, 5 ve 15 kat olarak farklı miktarlarda gerçekleştirildi. Kaplama işleminden sonra, ince film kaplı alttaşlar, kare bir fırın içerisine konuldu ve 500 oC de 30 dk tavlandı. Yapı karakterizasyonu ve yüzey morfolojisi, X-ışını kırınımı metodu (X-ray diffraction; XRD) ve taramalı elektron mikroskobu (scanning electron microscopy; SEM) kullanılarak analiz edildi. Her bir n-ZnO/p-Si heteroeklem güneş hücresi yapısı için, kısa devre akımı (Isc) ve açık devre voltajı (Voc) elektriksel ölçümler ile tespit edildi ve verimlilik (h) hesapları yapıldı. Tüm işlemler oda sıcaklığında gerçekleştirildi. Yapılan bu çalışmaya göre, güneş hücrelerinin verimi, kritik bir kalınlığa kadar, ZnO kaplama miktarının artışı ile artmakta, kritik kalınlık aşıldığında (daha fazla ZnO kaplama yapıldığında) da düşmektedir. Buradan, ZnO kaplama miktarının (ZnO tabaka kalınlığının) güneş hücrelerinin performansını etkileyen önemli bir parametre olduğu sonucuna varıldı. The Effect of ZnO Coating Amount on The Efficiency of n-ZnO/p-Si Heterojunction Solar Cell Abstract In this study, the effect of zinc oxide (ZnO) coating amount on the efficieny of n-type zinc oxide/p-type silicon (n-ZnO/p-Si) heterojunction solar cell was investigated. ZnO nanoparticles were synthesized by sol gel method. The synthesized nanoparticles were coated on glass substrates and p-Si substrates using spin coating method. The coating process was carried out in different amounts as 2, 4, 5 and 15 times. After the coating process, the thin film coated substrates were placed in a square furnace and annealed at 500 oC for 30 min. Structure characterization and surface morphology were analyzed using X-ray diffraction (XRD) method and scanning electron microscopy (SEM). For each n-ZnO/p-Si heterojunction solar cell structure, short circuit current (Isc) and open circuit voltage (Voc) were determined by electrical measurements and efficiency (h) calculations were made. All processes were performed at room temperature. According to this study, the efficiency of solar cells increases with increasing the amount of ZnO coating up to a critical thickness and decreases when the critical thickness is exceeded (more ZnO coating is done). From this it was concluded that the amount of ZnO coating (ZnO layer thickness) is an important parameter affecting the performance of solar cells. Gökhan ALGÜN, ORCID: https://orcid.org/0000-0002-4607-3382

In this study, the effect of strontium (Sr) concentration on the ultrafast humidity sensing performance of Sr doped zinc oxide (SrxZn1–xO) nanostructured thin films was reported. The sol gel method was used in the synthesis of undoped zinc oxide (ZnO) and SrxZn1–xO (x = 0.01, 0.02, 0.03, 0.04, and 0.10) nanoparticles. According to the x-ray diffraction analysis, all films had a hexagonal wurtzite structure. By doping Sr into the ZnO lattice, the preferential orientation changed from the (002) plane to the (101) plane. Scanning electron microscopy micrographs showed that all films had a structure containing nanosized grains and capillary-nanopores, and the nanosized grains were homogeneously and uniformly distributed on the surface of films. The presence of zinc, oxygen and Sr elements in nanostructured thin films was proved by energy dispersive x-ray spectra. The relative humidity sensing performances of undoped ZnO and SrxZn1–xO films were tested with electrical resistance measurements in the range of 40–90% RH at room temperature. SrxZn1–xO films had high sensitivity, excellent stability, reliable and reproducible character, and fast response and recovery times. Sr0.10Zn0.90O was accepted as the best sample in terms of having the highest humidity sensitivity (657.59x) and the fastest response (0.8 s) and recovery (9.8 s) times. This study clearly revealed that SrxZn1–xO nanostructured thin films have great potential for high performance humidity sensor applications due to their ultrafast humidity sensing performance. Highlights: Sol–gel method to synthesize Sr-doped ZnO nanoparticles. For RH-sensing performances, electrical resistance changes depending on %RH. Structural, morphological and elemental analyses with XRD, SEM and EDS. High-humidity sensitivity of 657.59x with Sr doping into ZnO. Ultra-fast response (0.8 s) and recovery (9.8 s) times with Sr doping into ZnO. [ABSTRACT FROM AUTHOR]

In this study, the effect of cerium (Ce) concentration on humidity sensing performance of humidity sensors based on Ce-doped zinc oxide nanostructure was investigated. Undoped ZnO (uZnO) and Ce-doped zinc oxide (CZO) nanoparticles were synthesized by sol–gel method. X-ray diffraction analyzes revealed that all nanostructures have a hexagonal wurtzite crystal structure and preferential orientation along the (002) plane. Scanning electron microscopy micrographs showed that there are homogeneously and uniformly distributed nanosized grains and capillary-nanopores on the surfaces of nanostructures. The energy dispersive x-ray spectroscopy analyzes confirmed the presence of zinc, oxygen and Ce elements in the nanostructures. The relative humidity (RH) sensing performances of uZnO and CZO nanostructured sensors were determined by means of electrical resistance measurements in the range of 40–90% RH at room temperature. The humidity sensing performance of the zinc oxide (ZnO) nanostructured sensor was significantly increased by Ce doping. All of the CZO sensors showed very high sensitivity to humidity and very short response and recovery times were achieved. It has been determined that 3 mol% Ce-doped ZnO has the best crystallite quality, the highest humidity sensitivity with a ratio of 7490 in the range of 40–90% RH, and the fastest times with a response time of 0.8 s and a recovery time of 4.7 s. This study clearly showed that CZO nanostructures, which we produce easily and at low cost, have the ideal humidity sensor potential and therefore have a bright future for humidity sensor applications. [ABSTRACT FROM AUTHOR]

This study reports the humidity sensing characteristics of aluminum (Al) and fluorine (F) co-doped zinc oxide (ZnO) nanostructured thin films with different Al concentrations. Sol–gel method was used in the synthesis of Al and F doped ZnO nanoparticles. The Al concentration was changed to 0.5 mol%, 1 mol% and 1.5 mol% while F concentration was kept constant at 2 mol%. Al and F co-doped ZnO (AFZO) nanostructured thin films for manufacturing relative humidity (RH) sensors were fabricated on glass substrates with a dip coating technique and then annealed at 500 °C for 1 h. The scanning electron microscopy (SEM) micrographs indicated that all AFZO films had uniform and homogeneous surfaces. The X-ray diffraction (XRD) patterns revealed that AFZO films were polycrystalline and have a hexagonal wurtzite structure with a preferential orientation along the (002) plane. The RH sensing characteristics of AFZO sensors was determined by electrical resistance measurements in the range of 40–90% RH at room temperature (RT). Both the electrical resistivity and RH sensing characteristics of AFZO sensors were found to be highly dependent on the Al concentration. All AFZO sensors exhibited high sensitivity, excellent stability, fast response and recovery times and a repeatable characteristic. The lowest electrical resistivity and best humidity sensor characteristics were obtained for AFZO sensor containing 1 mol% Al (AFZO–010). The sensitivity ratio between 40 and 90% RH is approximately 247 × for AFZO–010. This study showed that AFZO nanostructured thin films are promising for high performance humidity sensor applications. [ABSTRACT FROM AUTHOR]

In this study, the effect of fluorine (F) doping on the humidity sensing properties of F doped zinc oxide structures was investigated. Undoped zinc oxide (ZnO) and F doped zinc oxide (FZO) nanoparticles were synthesized by sol gel method. The synthesized nanoparticles were coated on glass substrates by dip coating method. In the coating process, the glass substrates were immersed in undoped ZnO and FZO solutions and withdrawn at a rate of 25 cm/s at room temperature. Then, the thin film coated glasses are annealed in a square furnace at 500 °C for 1 h. Structural analyzes of the produced thin films were performed using X-ray diffraction and scanning electron microscopy. The thin film nanostructures were placed in the homemade system in order to investigate the humidity sensing characteristics such as relative humidity dependent resistance change, sensitivity, hysteresis, stability, response and recovery times and reproducibility. As a result, it is predicted that the FZO structures can be used in the humidity sensing applications and it is determined that the optimal F additive amount for application is 2 mol%. [ABSTRACT FROM AUTHOR]

In this study the structural, optical, electrical properties and solar cell performance of undoped ZnO and rare earth (RE) doped ZnO (Zn0.95Yb0.05O, Zn0.95Eu0.05O and Zn0.90 Eu0.05Yb0.05O) thin films prepared by sol-gel spin coating method were investigated. The structural characterizations of the obtained samples were examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analyses. The optical properties of these thin films were carried out with UV-vis transmittance spectroscopy technique in 350-800 nm range. The electrical properties of films were examined by resistance measurements at room temperature. XRD results show that all samples have single phase wurtzite (hexagonal) structure with (002) c-plane orientation. Detailed structural characterizations were examined from XRD data. SEM analysis represents that nanoparticles are formed on the thin films and the type of dopant affected the morphologies, thickness and sizes of ZnO nanostructures. Our optical results indicate the average optical transmittances of RE doped ZnO samples are 98% at different regions in the visible region. Also the band gap energy of all of thin films was calculated from optical transmittance spectroscopy data using Tauc equation. The band gap energies of undoped, Yb, Eu, and Eu/Yb co-doped ZnO were found as 3.307, 3.295, 3.29 and 3.28 eV, respectively. Urbach energy was calculated from spectral absorption coefficient and this value shows an increase with doping Eu and Yb elements. It was observed that the electrical resistivity of doped samples is low compared to ZnO thin film. Also, in this study the rare earth elements effects on the solar cell performance of ZnO nanostructures were investigated and it was seen that Yb and Eu elements improve the cell performance. [ABSTRACT FROM AUTHOR]

The paper reports the fabrication of zinc oxide/porous silicon (ZnO/PS) heterojunction solar cells based on porous material and the effects of etching current density and porous structure on the performance of these solar cells. PS samples were produced by electrochemical etching on a p-type crystalline-silicon (c-Si) wafer with boron (B) doped and (111) orientation. The etching process was carried out in a HF:C2H5OH (1:3) electrolyte solution at different etching current densities of 5, 10, 15, and 25 mA/cm2 for 15 min at room temperature (RT). ZnO nanoparticles synthesized by sol–gel method were coated on PS layers by the sol–gel spin coating technique at a speed of 300 rpm for 20 s at RT for fabrication of ZnO/PS heterojunction solar cells. The structural analyses were performed using a field emission scanning electron microscope. Depending on the increase of etching current density, the pore diameter and porosity in the etched structures increased approximately from 200 to 920 nm and from 19 to 62%, respectively. Reflection characteristics of ZnO/PS heterojunction solar cells were determined using reflection measurements. The lowest optical reflection was obtained in ZnO/PS heterojunction solar cell with PS layer formed at high etching current density. The dark I–V measurements indicated that all the solar cells exhibited a typical rectifying behavior, and the ideality factor increased with the increase of etching current density. Light I–V measurements were performed under AM1.5G conditions. The short circuit current, open circuit voltage, and energy conversion efficiency (η) increased with the increase of etching current density. The best photovoltaic performance was obtained in ZnO/PS heterojunction solar cell having the PS layer produced at high etching current density of 25 mA/cm2. The highest energy conversion efficiency of 6.05% was obtained in this solar cell. It was determined that the etching current density and porous structure are important parameters affecting the photovoltaic performance of ZnO/PS heterojunction solar cells. [ABSTRACT FROM AUTHOR]