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[IEEE 2017 IEEE 44th Photovoltaic Specialists Conference (PVSC) - Washington, DC (2017.6.25-2017.6.30)] 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC) - Interface Effects of Alkali Treatment on Cu-Rich Thin Film Solar Cells
摘要： CuInSe2 absorbers grown under Cu-excess have better current collection compared to those grown as Cu-poor. However, cells based on Cu-excess absorbers show lower efficiency due to a worse absorber-buffer interface where the interface recombination is the dominant recombination path. In this paper, potassium fluoride post-deposition treatment is used to improve this interface, as evidenced by an activation energy of the main recombination path close to the band gap energy. The treatment also succeeded in eliminating the 200-meV step observed in admittance measurements; a main characteristic of Cu-excess CuInSe2 cells.
关键词： admittance measurements,Cu-excess,interface recombination,potassium fluoride post-deposition treatment,CuInSe2
更新于2025-11-14 17:28:48
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Contactless Optical Characterization of Carrier Dynamics in Free-Standing InAs-InAlAs Core-Shell Nanowires on Silicon
摘要： Contactless time-resolved pump-probe and external quantum efficiency measurements were performed on epitaxially grown free-standing wurtzite indium arsenide/indium aluminum arsenide (InAs-InAlAs) core-shell nanowires on Si (111) substrate from 77K to 293K. The first independent investigation of Shockley-Read-Hall, radiative and Auger recombination in InAs-based NWs is presented. Although the Shockley-Read Hall recombination coefficient was found to be at least two orders of magnitude larger than the average experimental values of other reported InAs materials, the Auger recombination coefficient was reported to be ten-fold smaller. The very low Auger and high radiative rates result in an estimated peak internal quantum efficiency of the core-shell nanowires as high as 22% at 77K, making these nanowires of potential interest for high efficiency mid-infrared emitters. A greater than two-fold enhancement in minority carrier lifetime was observed from capping nanowires with a thin InAlAs shell due to passivation of surface defects.
关键词： Auger recombination rate,radiative,Shockley-Read-Hall,Pump-probe spectroscopy,core-shell nanowires,surface/interface recombination velocity,minority carrier lifetime
更新于2025-09-23 15:23:52
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Aqueous Solution Processed Copper Iodide as Hole Transport Material For Planar Inverted Perovskite Solar Cells
摘要： The inorganic carrier transport layers are robust and stable to the environment compared to the organic hole transport layer (HTL). Here, we report on the fabrication of the halide perovskite devices employing CuI as HTL and explored material properties and optoelectronic characterizations. The CuI device demonstrated the device efficiency of 14.1%. The film morphology of CuI is found to have the influence on the perovskite film growth and hence affected on the device parameters. The interface activation energy (EA) ~Eg suggests the recombination activities in the perovskite bulk is dominant. The capacitance analysis revealed the two trap centers of 0.527 eV and 0.332 eV in the perovskite bulk.
关键词： capacitance spectra,interface recombination,defect,copper iodide,halide perovskite
更新于2025-09-23 15:21:01
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Role of surface recombination in perovskite solar cells at the interface of HTL/CH3NH3PbI3
摘要： In order to achieve the highest performance of organometal trihalide perovskite solar cells, it is required to recognize the dominant mechanisms which play a key role in a perovskite material. In the following studies, we have focused on the interfacial recombination between the hole transporting layer (HTL) and the perovskite CH3NH3PbI3 in solar cell devices with p–i–n architecture. It has been shown that Cu∶NiOx used as HTL drastically decreases a short–circuit photocurrent (Jsc) and an open–circuit voltage (Voc). However, we have found that an addition of PTAA thin layer improves cells quality and, as a consequence, the efficiency of such solar cells increases by 2%. Here, we explain both Jsc and Voc losses with a theory of the "dead layer" of perovskite material where a very high surface recombination occurs. We demonstrate the numerical and experimental studies by the means of series detailed analyses to get in–depth understanding of the physical processes behind it. Using a drift–diffusion model, it is shown that the presence of a parasitic recombination layer influences mostly the current distribution in the simulated samples explaining Jsc and Voc losses. The following results could be useful for improving the quality of perovskite solar cells.
关键词： dead layer recombination,perovskite solar cell,interface recombination
更新于2025-09-19 17:13:59
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Charge Carrier Collection and Contact Selectivity in Solar Cells
摘要： The electronic properties of the contacts to a photovoltaic absorber material are important for the final efficiency of any type of solar cell. For highly efficient solar cells based on high quality absorber materials like single-crystalline silicon, polycrystalline Cu(In,Ga)Se2, CdTe, or metal-halide perovskites, contact formation is even the decisive processing step determining the final efficiency. The present paper combines recently developed quantitative concepts for the description of contacts to solar cells in terms of their selectivity toward a more general description that is valid for all types of solar cells and all types of contacts. It is shown that the built-in voltage is an important parameter to influence the selectivity of contacts to photovoltaic absorber materials. It is also shown that the contact selectivity is mathematically related to the collection efficiency which can be measured by luminescence based techniques.
关键词： solar cells,charge extraction,surface recombination,photovoltaics,interface recombination
更新于2025-09-19 17:13:59
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Double-Mesoscopic Hole-Transport-Material-Free Perovskite Solar Cells: Overcoming Charge-Transport Limitation by Sputtered Ultra-Thin Al <sub/>2</sub> O <sub/>3</sub> Isolating Layer
摘要： The electrically insulating space layer takes a fundamental role in monolithic carbon-graphite based perovskite solar cells (PSCs) and it has been established to prevent the charge recombination of electrons at the mp-TiO2/carbon-graphite (CG) interface. Thick 1 μm printed layers are commonly used for this purpose in the established triple-mesoscopic structures to avoid ohmic shunts and to achieve a high open circuit voltage. In this work, we have developed a reproducible large-area procedure to replace this thick space layer with an ultra-thin dense 40 nm sputtered Al2O3 which acts as highly electrically insulating layer preventing ohmic shunts. Herewith, transport limitations related so far to the hole diffusion path length inside the thick mesoporous space layer have been omitted by concept. This will pave the way towards the development of next generation double-mesoscopic carbon-graphite based PSCs with highest efficiencies. Scanning electron microscope (SEM), energy dispersive x-ray analysis (EDX) and atomic force microscopy (AFM) measurements show the presence of fully oxidized sputtered Al2O3 layer forming a pseudo-porous covering of the underlying mesoporous layer. The thickness has been finely tuned for the achievement of both electrical isolation and optimal infiltration of the perovskite solution allowing full percolation and crystallization. Photo voltage decay, light-dependent and time-dependent photoluminescence measurements showed that the optimal 40 nm thick Al2O3 not only prevents ohmic shunts but also efficiently reduces the charge recombination at the mp-TiO2/CG interface and, at the same time, allows efficient hole diffusion through the perovskite crystals embedded in its pseudo-pores. Thus, stable VOC of 1 V using CH3NH3PbI3 perovskite has been achieved under full sun AM 1.5 G with stabilized device performance of 12.1%.
关键词： Perovskite solar cells,Al2O3 Space layer,Double-mesoscopic,Carbon-graphite,HTM-free,Sputtering,Interface recombination
更新于2025-09-19 17:13:59
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Energy level alignment and nanoscale investigation of a-TiO <sub/>2</sub> /Cu-Zn-Sn-S interface for alternative electron transport layer in earth abundant Cu-Zn-Sn-S solar cells
摘要： Efficiency of earth abundant and pure sulfide kesterite Cu-Zn-Sn-S (CZTS) solar cell has been stagnant around 9.4% for years, while its counterpart Cu-In-Ga-Se (CIGS) reports an efficiency of more than 22%. Low open circuit voltage (VOC) is the major challenging factor for low efficiency due to severe nonradiative interface recombinations. The existence of higher defect states at the conventional CZTS-CdS interface due to undesirable energy level alignment and lattice misfit promotes trap-assisted recombinations and results in low VOC. In this work, amorphous TiO2 (Eg = 3.8 eV) is proposed as a promising substitute to the conventional and low bandgap CdS (Eg = 2.4 eV) layer. The surface and interface of the CZTS-TiO2 layer were investigated using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The result reveals favorable "spike"-like conformations at the CZTS-TiO2 interface with a conduction band offset value of 0.17 eV. The nanoscale probing of the interface by Kelvin probe force microscopy across CZTS-TiO2 layers shows a higher potential barrier for interface recombination at CZTS-TiO2 in contrast to the conventional CZTS-CdS interface. Finally, the fast decay response and lower persistent photoconductivity of photogenerated carriers for CZTS-TiO2 heterojunction based photodetectors further validate our results. The energy level alignment and nanoscale interface studies signify TiO2 as a promising alternate buffer layer for earth abundant CZTS solar cells.
关键词： XPS,TiO2,CZTS,CdS,energy level alignment,KPFM,UPS,solar cells,interface recombination
更新于2025-09-16 10:30:52
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Achieving efficient flexible perovskite solar cells with room-temperature processed tungsten oxide electron transport layer
摘要： For flexible perovskite solar cells, achieving high power conversion efficiency by using a room-temperature technology to fabricate a compact electron transport layer is one of the best options. Here, we develop an annealing-free, dopant-free, and amorphous tungsten oxide as electron transport layer by vacuum evaporation for flexible perovskite solar cells. The compact amorphous tungsten oxide electron transport layer with different thicknesses (0–50 nm) was directly deposited on flexible PEN/ITO substrate. A model of the improvement mechanism is proposed to understand how the thickness tailoring simultaneously enhances the crystallization and relaxes the trade-off between interface recombination and charge transfer. By optimizing the amorphous tungsten oxide thickness, the high homogeneous, uniform, and dense electron transport layer with a thickness of 30 nm is found to not only decrease the pinhole of the perovskite layer, but also enhance charge transport with reducing resistance. Furthermore, the mechanical bending stability revealed that, the fabricated perovskite solar cells show stable power conversion efficiency up to more than 1000 bending cycles. The room-temperature processed fabrication enables the amorphous tungsten oxide to become a potential electron transport layer candidate for the large-scale flexible perovskite solar cells, which becomes compatible with practical roll-to-roll solar cells manufacturing.
关键词： Electron transport layer,Amorphous tungsten oxides,Low temperature,Flexible solar cells,Interface recombination
更新于2025-09-16 10:30:52
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Improved Interface Charge Extraction by Double Electron Transport Layers for High‐Efficient Planar Perovskite Solar Cells
摘要： Charge extraction by electron transport layers (ETLs) plays a vital role in improving the performance of perovskite solar cells (PSCs). Here, PSCs with four different types of ETLs, such as SnO2, amorphous-Zn2SnO4 (am-ZTO), am-ZTO/SnO2, and SnO2/am-ZTO, are successfully synthesized. The interface recombination behavior and the charge transport properties of the devices affected by four types of ETLs are systematically investigated. For dual am-ZTO/SnO2 ETLs, compact am-ZTO ETL prepared by the pulsed laser deposition method provides a dense physical contact with FTO than the spin coating films, decreasing leakage current and improving charge collection at the interface of ETL/FTO. Moreover, dual am-ZTO/SnO2 ETLs lead to large free energy difference (ΔG), improving electron injection from perovskite to ETLs. One additional electron pathway from perovskite to am-ZTO is formed, which can also improve electron injection efficiency. A power conversion efficiency of 20.04% and a stabilized efficiency of 19.17% are achieved for the device based on dual am-ZTO/SnO2 ETLs. Most importantly, the devices are fabricated at a low temperature of 150 °C, which offers a potential method for large-scale production of PSCs, and paves the way for the development of flexible PSCs. It is believed that this work provides a strategy to design ETLs via controlling ΔG and interface contact to improve the performance of PSCs.
关键词： amorphous-Zn2SnO4/SnO2,charge transport,perovskite solar cells,interface recombination
更新于2025-09-11 14:15:04
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Annealing effects on recombinative activity of nickel at direct silicon bonded interface
摘要： By performing capacitance transient analyses, the recombination activity at a (110)/(100) direct silicon bonded (DSB) interface contaminated with nickel diffused at different temperatures, as a model of grain boundaries in multicrystalline silicon, was studied. The trap level depth from the valence band, trap density of states, and hole capture cross section peaked at an annealing temperature of 300 ?C. At temperatures (cid:62)400 ?C, the hole capture cross section increased with temperature, but the density of states remained unchanged. Further, synchrotron-based X-ray analyses, microprobe X-ray fluorescence (μ-XRF), and X-ray absorption near edge structure (XANES) analyses were performed. The analysis results indicated that the chemical phase after the sample was annealed at 200 ?C was a mixture of NiO and NiSi2.
关键词： direct silicon bonded interface,recombination activity,annealing effects,X-ray analyses,nickel,capacitance transient analyses
更新于2025-09-04 15:30:14