Inorganic–organic perovskites like methylammonium-lead-iodide have proven to be an effective class of materials for fabricating efficient solar cells. To improve their performance, light management ...techniques using textured surfaces, similar to those used in established solar cell technologies, should be considered. Here, we apply a light management foil created by UV nanoimprint lithography on the glass side of an inverted (p-i-n) perovskite solar cell with 16.3% efficiency. The obtained 1 mA cm–2 increase in the short-circuit current density translates to a relative improvement in cell performance of 5%, which results in a power conversion efficiency of 17.1%. Optical 3D simulations based on experimentally obtained parameters were used to support the experimental findings. A good match between the simulated and experimental data was obtained, validating the model. Optical simulations reveal that the main improvement in device performance is due to a reduction in total reflection and that relative improvement in the short-circuit current density of up to 10% is possible for large-area devices. Therefore, our results present the potential of light management foils for improving the device performance of perovskite solar cells and pave the way for further use of optical simulations in the field of perovskite solar cells.
The rear side of a silicon solar cell is often designed to minimize surface recombination, series resistance, and cost, but not necessarily parasitic absorption. We present a comprehensive study of ...parasitic absorption in the metal layer of solar cells with dielectric/metal rear reflectors. The sub-bandgap reflectance of a solar cell or test structure is proposed as an experimentally accessible probe of parasitic absorption, and it is correlated with short-circuit current density. The influence of surface texture, dielectric refractive index and thickness, and metal refractive index on sub-bandgap reflectance—and thus current—is then both calculated and measured. From the results, we formulate design rules that promote optimum infrared response in a wide variety of silicon solar cells.
•Comprehensive analysis of the reflectance of dielectric/metal reflectors at the rear of silicon solar cells.•Sub-bandgap reflectance is a readily measureable metric of parasitic absorption and is correlated with short-circuit current density.•Calculation and measurement of sub-bandgap reflectance for common textures, dielectrics, and metals.•General design rules for optimizing rear reflectance: low-refractive-index dielectrics at least 100nm thick suppress absorption in even relatively poor metal reflectors.
We present an optical optimization on a red bottom-emitting OLED with an enhanced cavity in combination with external outcoupling textures, periodically positive and negative hexagonal dome-shaped ...structures. A coupled optical modeling, combining simulations of coherent planar and incoherent structured layers, is verified and employed for optimization of the OLED structure and applied textures. Special attention is paid on the study of optical effects, related to the limited device area. Using optical modeling, we present and quantify main optical losses in the device. We show the importance of considering external outcoupling structures in optimization of thicknesses of organic films, which define the optical cavity. When optimized, an OLED with 50.5% light extraction efficiency (39.4% external quantum efficiency) and improved angular intensity distribution is predicted for devices with positive shaped dome structures. This approach allows for global efficiency optimization of complete OLEDs, comprising arbitrarily shaped outcoupling structures.
We demonstrate a monolithic perovskite/CIGS tandem solar cell with a certified power conversion efficiency (PCE) of 24.2%. The tandem solar cell still exhibits photocurrent mismatch between the ...subcells; thus optical simulations are used to determine the optimal device stack. Results reveal a high optical potential with the optimized device reaching a short-circuit current density of 19.9 mA cm–2 and 32% PCE based on semiempirical material properties. To evaluate its energy yield, we first determine the CIGS temperature coefficient, which is at −0.38% K–1 notably higher than the one from the perovskite subcell (−0.22% K–1), favoring perovskite in the field operation at elevated cell temperatures. Both single-junction cells, however, are significantly outperformed by the combined tandem device. The enhancement in energy output is more than 50% in the case of CIGS single-junction device. The results demonstrate the high potential of perovskite/CIGS tandem solar cells, for which we describe optical guidelines toward 30% PCE.
Perovskite solar cells (PSC) have shown that under laboratory conditions they can compete with established photovoltaic technologies. However, controlled laboratory measurements usually performed do ...not fully resemble operational conditions and field testing outdoors, with day‐night cycles, changing irradiance and temperature. In this contribution, the performance of PSCs in the rooftop field test, exposed to real weather conditions is evaluated. The 1 cm2 single‐junction devices, with an initial average power conversion efficiency of 18.5% are tracked outdoors in maximum power point over several weeks. In parallel, irradiance and air temperature are recorded, allowing us to correlate outside factors with generated power. To get more insight into outdoor device performance, a comprehensive set of laboratory measurements under different light intensities (10% to 120% of AM1.5) and temperatures is performed. From these results, a low power temperature coefficient of −0.17% K−1 is extracted in the temperature range between 25 and 85 °C. By incorporating these temperature‐ and light‐dependent PV parameters into the energy yield model, it is possible to correctly predict the generated energy of the devices, thus validating the energy yield model. In addition, degradation of the tested devices can be tracked precisely from the difference between measured and modelled power.
In this paper, laboratory and rooftop performance of perovskite solar cells under changing temperature and irradiance is analyzed. By integrating laboratory data trends and measured weather data into optical energy yield model, the temperature‐dependent energy yield model is developed and validated, and can be used to predict generated energy of perovskite solar cells or track their degradation during field testing.
In the scope of solar cell characterisation, spatially resolved imaging (SRI) methods (EL, PL and LBIC) have long been a standard procedure for valuable in-depth evaluation and extraction of various ...spatially resolved material properties, especially those related to the electrical behaviour. While this extraction can be straightforward in the case of laterally homogeneous devices, the situation is vastly different when the structural features are laterally varying, such as in the case of interdigitated back contact (IBC) solar cells. We show that in the case of laterally varying devices inherent device optical properties play a far more important role in determining the measured profile in this case and may indeed overshadow any underlying electrical effects. We therefore propose and validate a methodology that couples SRI characterisation with advanced bottom-up simulation of IBC solar cells. The method fully accounts for lateral device variability and allows for accurate extraction of the underlying electrical phenomena. We demonstrate the applicability of the method on state-of-the-art high-efficiency IBC solar cells, and explain the key factors, which could lead to misinterpretation of the results obtained solely by SRI measurements.
•Interpretation of measured IBC electroluminescence profiles through opto-electrical simulation.•Decoupling of underlying optical and electrical phenomena.•Device optics overshadows recombination driven fluctuations of luminescence profiles.•Rear interface strongly influences the shape of the extracted luminescence profile.•Shape of the luminescence profile is highly dependent on imaging system’s aperture.
Accurate forecasting of yearly energy yield of photovoltaic devices under realistic operating conditions is key for numerous practical applications related to further evolution of photovoltaics. In ...this work we present development and validation of an energy yield model applied to planar perovskite solar cells. The model is based on the combination of advanced optical modelling and extensive opto-electrical characterization and takes the geographical location and the orientation of the device into account. Using the model, we first perform a detailed sensitivity analysis and indicate the key parameters and their interdependencies that most significantly affect the calculated energy yield values. We show that the results are dominated (within 4% of the final value) by the solar irradiance dependency of the short-circuit current density, and further by the temperature dependency of the open-circuit voltage and the fill factor, whereas the irradiance dependency of the open-circuit voltage and the fill factor are mutually compensated. In the second part of the paper, we investigate how the energy yield of the device is affected by the application of external light management foils. Different texture morphologies, geographical locations, and device orientations are included in the investigation. The results show that even under realistic operating conditions, the overall trends of the light management efficiency of textured foils are not that different from those observed under standard test conditions; the highest energy yield gains in the order of 7–11% are obtained by the tetrahedral texture which is indicated as optimal in all studied cases.
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•EY forecasting crucial for LCOE estimation, degradation monitoring, and device optimization.•JSC under realistic conditions can be simulatend using advanced optical modelling.•VOC and FF under realistic conditions can be obtained through extensive electrical characterization.•External light management foils provide significant EY boosts under realistic outdoor conditions; tetrahedral micro texture indicated as the optimal in all studied cases.•Similar trends observed as under STC conditions, with similar achievable relative gains.
Metastability of many-body quantum states is rare and still poorly understood. An exceptional example is the low-temperature metallic state of the layered dichalcogenide 1T-TaS
in which electronic ...order is frozen after external excitation. Here we visualize the microscopic dynamics of injected charges in the metastable state using a multiple-tip scanning tunnelling microscope. We observe non-thermal formation of a metastable network of dislocations interconnected by domain walls, that leads to macroscopic robustness of the state to external thermal perturbations, such as small applied currents. With higher currents, we observe annihilation of dislocations following topological rules, accompanied with a change of macroscopic electrical resistance. Modelling carrier injection into a Wigner crystal reveals the origin of formation of fractionalized, topologically entangled networks, which defines the spatial fabric through which single particle excitations propagate. The possibility of manipulating topological entanglement of such networks suggests the way forward in the search for elusive metastable states in quantum many body systems.
We developed a fully scalable quasi‐SPICE approach for electrical modelling of stress‐induced inhomogeneities in crystalline silicon solar cells, based on damage detected by electroluminescence ...imaging. We present a model of active and inactive microcracks, highlight their effects on the current‐voltage characteristic, and validate the model on a number of experimental cases. The generalisation of our model to a complexly damaged solar cell shows excellent agreement with the measurements, with only 0.12% estimation error of the power loss of the complexly damaged cell. The ability to accurately model fundamental stress induced inhomogeneities, and their effects on cell level is crucial to estimating long‐term performance degradation and energy yield of installed photovoltaic modules throughout their lifetime. The developed scalable model paves a path to intricate, statistically supported modelling for power loss prediction and mitigation in solar cells, photovoltaic modules, and photovoltaic arrays caused by mechanically induced inhomogeneities.
A fully scalable quasi‐SPICE approach for electrical modelling of stress‐induced inhomogeneities in crystalline silicon solar cells, based on damage detected by electroluminescence imaging, was validated on a number of experimental cases. The model exhibits a 0.12% power loss estimation error in the maximum power point of a complexly damaged solar cell.
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