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Device simulation of Cu(In,Ga)Se2 solar cells by means of voltage dependent admittance spectroscopy
摘要： The simulation of solar cell devices is important for the understanding of defect physics and loss mechanisms in real solar cells. On the other hand, voltage dependent admittance spectroscopy delivers essential information for establishing a baseline simulation model of Cu(In,Ga)Se2 (CIGSe) solar cells. Here we give an explanation for the weak temperature dependence of the N1-signal, the latter being not compatible with a bulk defect or with a simple hole barrier at the Mo back contact. Furthermore, we find a Ed,IF – EV ≈ 0.3 eV deep recombination-active acceptor state at the absorber/buffer interface made of air-light exposed CIGSe absorbers. This gives us the ability to explain the reduction of power conversion efficiency of solar cells made from air-light exposed absorbers. From the voltage dependent capacitance step of this interface defect we can deduce the formerly unknown position of the Fermi level at the hetero junction in equilibrium which is close to mid-gap. Simulation of dark J-V curves allows a refinement of the parameter of this absorber/buffer interface defect, resulting in a defect density of Nd,IF ≈ 3.5·1011 cm-2 as well as capture cross sections of σn ≈ 4·10-16 cm2 for electrons and σp ≈ 3·10-11 cm2 for holes.
关键词： device simulation,Cu(In,Ga)Se2,admittance spectroscopy,defect physics,solar cells
更新于2025-11-14 17:28:48
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Electrical and optical properties of organic light-emitting diodes with rhenium(I) complexes using DC and AC methods
摘要： Four rhenium(I) tricarbonyl complexes with 1,10-phenanthroline and derivative bearing electron-donating CH3 and OCH3 substituents were doped into host material poly (9-vinylcarbazole) (PVK) with a mass ratio of 8% as the emissive layer in organic light-emitting diodes (OLEDs). All complexes showed photoluminescence in the solution and embedded into a PVK matrix (λmax～520–550 nm). The comparison with the bare PVK emission and the compound/PVK ?lm shows that the emission of the polymer was quenched through an energy transfer process from PVK to the dopant. The electrical properties of the devices with FTO/PEDOT:PSS/Complex:PVK/Al architecture were investigated using the DC method by curves of current density-voltage and the AC method as admittance spectroscopy, which showed that the behavior of the devices is controlled by charge carrier injection rather than bulk transport.
关键词： Energy transfer,Re(I) complexes,Charge injection,Admittance spectroscopy,Emission,OLEDs
更新于2025-11-14 17:28:48
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Can we see defects in capacitance measurements of thin‐film solar cells?
摘要： Thermal admittance spectroscopy and capacitance‐voltage measurements are well established techniques to study recombination‐active deep defect levels and determine the shallow dopant concentration in photovoltaic absorbers. Applied to thin‐film solar cells or any device stack consisting of multiple layers, interpretation of these capacitance‐based techniques is ambiguous at best. We demonstrate how to assess electrical measurements of thin‐film devices and develop a range of criteria that allow to estimate whether deep defects could consistently explain a given capacitance measurement. We show that a broad parameter space, achieved by exploiting bias voltage, time, and illumination as additional experimental parameters in admittance spectroscopy, helps to distinguish between deep defects and capacitive contributions from transport barriers or additional layers in the device stack. On the example of Cu(In,Ga)Se2 thin‐film solar cells, we show that slow trap states are indeed present but cannot be resolved in typical admittance spectra. We explain the common N1 signature by the presence of a capacitive barrier layer and show that the shallow net dopant concentration is not distributed uniformly within the depth of the absorber.
关键词： admittance spectroscopy,deep defects,doping profile,thin films,capacitance
更新于2025-09-19 17:13:59
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Influences of buffer material and fabrication atmosphere on the electrical properties of CdTe solar cells
摘要： The electrical properties such as interface energy barriers, defect energy levels, and densities dictate the performance of thin film solar cells. Here, we show that these properties can be quantified in cadmium telluride (CdTe) thin‐film solar cells using admittance spectroscopy‐based techniques. Our results reveal that the electrical properties in CdTe thin‐film solar cells depend on both buffer material and the fabrication atmosphere. We find that only a negligible front contact barrier exists at the CdS/CdTe front junction regardless of the fabrication atmospheres, while an obvious front barriers are observed at the ZnMgO (ZMO)/CdTe junctions. Both CdS/CdTe and ZMO/CdTe solar cells exhibit back contact barrier. The energy level of defects is shallower in CdS/CdTe cells than in ZMO/CdTe cells. The fabrication atmosphere influences the electrical properties, i.e., an oxygen‐free atmosphere reduces the front and back barrier heights and lowers the energy level of defects. The results provide critical insights for understanding and optimizing the performance of CdTe thin‐film solar cells.
关键词： admittance spectroscopy,interface barriers,cadmium telluride,equivalent circuit,photovoltaic cells
更新于2025-09-11 14:15:04
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Interface Properties of GaP/Si Heterojunction Fabricated by PE-ALD
摘要： The properties of n-GaP/p-Si interface as well as their influence on solar cell performance are studied for GaP layers grown by low-temperature (380 °C) plasma-enhanced atomic layer deposition (PE-ALD). The influence of different plasma treatments and RF power values are explored. The increase of RF power leads to a growth transition from amorphous (a-GaP) to microcrystalline GaP (μc-GaP) with either amorphous-GaP/Si or epitaxial-GaP/Si interface, respectively. However, when continuous hydrogen plasma is used the amorphous-GaP/Si interface exhibits better photovoltaic performance compared to the epitaxial one. Values of open circuit voltage, Voc ? 0.45–0.55 V and internal quantum efficiencies, IQE > 0.9 are obtained for amorphous-GaP/Si interfaces compared to Voc ? 0.25–0.35 V and IQE < 0.45 for epitaxial-GaP/Si interfaces. According to admittance spectroscopy and TEM studies the near-surface (30–50 nm) area of the Si substrate is damaged during growth with high RF power of hydrogen plasma. A hole trap at the level of EV t (0.33 ± 0.02) eV is detected by admittance spectroscopy in this damaged Si area. The damage of Si is not observed by TEM when the deposition of the structures with epitaxial-GaP/Si interface is realized by a modified process without hydrogen plasma indicating that the damage of the near-surface area of Si is related to hydrogen plasma interaction.
关键词： admittance spectroscopy,solar cells,PE-ALD,interface,GaP/Si heterojunction
更新于2025-09-04 15:30:14