Characterization Of Photovoltaic Devices Research Articles

Comparative of IEC 60891 and Other Procedures for Temperature and Irradiance Corrections to Measured I–V Characteristics of Photovoltaic Devices

The photovoltaic literature contains a wide range of methods for translating the I–V curves of a solar device to other conditions of irradiance and cell temperature, different from those under which the measurements were performed. Some of these translation methods are included as part of the International Standard IEC 60891. In this paper, these techniques are classified, reviewed, and implemented to perform a deep comparative analysis between them and to discuss their suitability for converting the I–V curves of photovoltaic modules under different scenarios of irradiance and temperature. From the analysis conducted, it can be seen that the interpolation method proposed in IEC 60891 achieves accurate results when it is applied to correct small and medium irradiance and temperature gaps. If no interpolation is possible and for large irradiance corrections, other procedures described in IEC 60891 can be applied. However, certain explicit methods based on the single-diode model or on the double-diode model can overcome the most well-known approaches proposed by the standard.

Importance of spectrally invariant broadband attenuation of light in indoor photovoltaic characterization

Indoor photovoltaic (IPV) devices are poised to make a significant contribution to the proliferation of the “Internet of Things” (IoT). For the accurate intercomparison of IPVs (and, hence, to advance the rational development of the technology), lighting conditions representative of those in typical indoor settings must be created reproducibly. As indoor lighting is invariably broadband, this will typically require the use of optical attenuation to achieve varying irradiance conditions at the device under test location. However, most forms of optical attenuation will suffer from some degree of spectral dispersion, creating sources of uncertainty for key figures of merit, such as power conversion efficiency. In this work, we examine the contribution of the mode of optical attenuation to the accurate characterization of IPV systems. We discuss requirements for broadband light source attenuation for the accurate characterization of photovoltaic devices under indoor illumination and consider the importance of using suitable reference devices for light intensity calibration. Furthermore, we experimentally verify attenuation methods typically used, including power control of the light source itself, use of neutral density filters, and advanced attenuation based on tandem prism attenuators. Finally, spectral shape alteration-induced uncertainties in performance parameter determination of photovoltaic cells under indoor illumination are quantified for three common broadband light attenuation methods, where we found ∼2%, ∼6%, and up to ∼15% ambiguity in photovoltaic device efficiency when using LED power control, prism attenuators, and neutral density filter-based broadband light attenuation, respectively.

Solar Cell Detection and Position, Attitude Determination by Differential Absorption Imaging in Optical Wireless Power Transmission

In optical wireless power transmission, position, size, and attitude of photovoltaic device (PV) must be determined from light source. A method proposed in the previous report is based on selective absorption characteristics of PV, and it is detected by differentiating images of strongly absorbable wavelength and one not. In this study, using two infrared wavelengths, two kinds of targets were detected by differential absorption imaging. One was a GaAs substrate which simulates diffuse rear surface, and the other was a real GaAs PV. It was found that the substrate’s reflective characteristic was diffuse, and the solar cell’s was mainly non-diffuse and accompanied by small diffuse component supporting wide-angle reflection. Using this feature, the position of the GaAs solar cell could be determined within a wide range of angle. Its attitude could also be determined with an accuracy of ±10 degrees to its normal. The position of diffuse GaAs substrate could be determined within a wide range of angles, and its attitude determination was proposed by exploiting its varying apparent size with tilt angle. Broad reflection characteristics of the GaAs substrate enabled attitude determination for a wide-angle range, and determination around normal would be erroneous.

Avoiding Ionic Interference in Computing the Ideality Factor for Perovskite Solar Cells and an Analytical Theory of Their Impedance-Spectroscopy Response

Impedance spectroscopy (IS) is a straightforward experimental technique that is commonly used to obtain information about the physical and chemical characteristics of photovoltaic devices. However, the nonstandard physical behavior of perovskite solar cells (PSCs), which are heavily influenced by the motion of mobile ion vacancies, has hindered efforts to obtain a consistent theory of PSC impedance. This work rectifies this omission by deriving a simple analytic model of the impedance response of a PSC from the underlying drift-diffusion model of charge-carrier dynamics and ion-vacancy motion, via an intermediate model that shows extremely good agreement with the drift-diffusion model in the relevant parameter regimes. Excellent agreement is demonstrated between the analytic impedance model and the much more complex drift-diffusion model for applied biases (including both open circuit and the maximum power point at 0.1 and 1 Sun) close to the cell's built-in voltage ${V}_{\mathrm{bi}}$. Both models show good qualitative agreement to experimental IS data in the literature and predict many of the observed anomalous features found in impedance measurements on PSCs. The analytic model provides a practical and useful tool with which to interpret PSC impedance data and extract physical parameters from IS experiments. We define a physical parameter, ${n}_{\mathrm{el}}$ (the electronic ideality factor), that is of particular significance to PSC physics, since, in contrast to the apparent ideality factor, the value of ${n}_{\mathrm{el}}$ can be used to identify the dominant source of recombination in the cell independent of its ionic properties.

Ferroelectric Materials for Solar Energy Scavenging and Photodetectors

AbstractThe photovoltaic devices based on ferroelectrics have drawn plenty of attention for providing a promising solar energy harvesting technology and efficient photodetectors. In this review, mainly the photoelectric properties of ferroelectric materials are introduced. First, three different types of ferroelectrics and primary representative materials are reviewed. Second, four existing principles and mechanisms of the photovoltaic effect in ferroelectrics are studied in great detail. Then, the typical design construction utilizing ferroelectrics for solar energy scavenging, photodetectors, and other photovoltaic device architectures is summarized. Lastly, the properties and characteristics of photovoltaic devices based on ferroelectrics are reviewed in the form of tables and the prospect of ferroelectric photovoltaic devices is discussed.

In data science we trust: Machine learning for stable halide perovskites

The exploration of the compositional space of halide perovskites is prohibitively costly using traditional experimental research strategies. Sun and colleagues demonstrated a physics-informed, machine-learning-guided, experimental approach that overturns this limitation enabling a rapid and efficient maximization of stability in mixed-cation perovskites.

Enhanced Efficiency and Stability of Planar Perovskite Solar Cells Using a Dual Electron Transport Layer of Gold Nanoparticles Embedded in Anatase TiO2 Films.

Incorporating plasmonic nanostructures is a promising strategy to enhance both the optical and electrical characteristics of photovoltaic devices via more efficient harvesting of incident light. Herein, we report a facile fabrication scheme at low temperature for producing gold nanoparticles embedded in anatase TiO2 films, which can simultaneously improve the efficiency and stability of n–i–p planar heterojunction perovskite solar cells (PSCs). The PSCs based on rigid and flexible substrates with 0.2 wt % Au–TiO2/TiO2 dual electron transport layers (ETLs) achieved power conversion efficiencies up to 20.31 and 15.36%, superior to that of devices with TiO2 as a single ETL. Moreover, 0.2 wt % Au–TiO2/TiO2 devices demonstrated significant stability in light soaking, which is attributed to improved light absorption, low charge recombination loss, and enhanced carrier transport, and extraction with the plasmonic Au–TiO2/TiO2 dual ETL. The present work improves the practicability of high-performance and flexible PSCs by engineering the photogenerated carrier dynamics at the interface.

Understanding the Photovoltaic Behavior of A-D-A Molecular Semiconductors through a Permutation of End Groups.

The facile synthesis of a series of benzodithiophene (BDT)- and indacenodithiophene (IDT)-based A-D-A oligomers with different end groups is reported, and their properties are studied by optical spectroscopy, electrochemistry, and density functional theory calculations. The permutation of central and terminal units tunes the optoelectronic properties and photovoltaic device characteristics in a predictable way, aiding in the rational design of small molecule semiconducting materials. Among the three rhodanine-derived terminal groups, N-alkylthiazolonethione revealed the strongest electron-withdrawing character, resulting in the lowest band gap, the highest stability, and the best photovoltaic device performance. The crystallographic analysis of two IDT derivatives yielded a highly unusual three-dimensional packing of the conjugated backbone, which is likely responsible for the remarkable photovoltaic performance of such A-D-A semiconductors.

High-speed digital light source photocurrent mapping system

High-resolution spatial characterization of photovoltaic devices and photodetectors can reveal local defects that can have a detrimental impact on the lifetime and performance of such devices. Photocurrent mapping methods can provide high-resolution measurements and characterization can be achieved under actual operating conditions. However, such methods usually require costly, complicated systems and possess limited measurement speed. In this work an optical system based on a digital micro-mirror device is used for photocurrent mapping and a measurement protocol with a theoretical upper limit for scanning rate of 22 kHz is presented. The digital micromirror device itself provides synchronised spatial and temporal modulation in order to perform current mapping. Photocurrent maps of solar cells devices obtained with a scanning rate of 1000 pixels in less than 6 s are reported (the speed was limited by the device’s response time and its photon to current conversion efficiency). The speed of photocurrent mapping is thus increased by almost two orders of magnitude compared to other methods and is only limited by the response of the device under test. A lateral resolution of 34 µm is achieved, with the potential to increase it even further. The absence of any moving parts allows high repeatability of measurements. Combined with the high-speed control of the light field, this enables the development of novel measurement techniques for the simultaneous measurement of temporal and spatial parameters. The fully digital control of the mapping system also presents a high potential for integration in industrial automated systems as it can be fully controlled using machine learning algorithms to achieve fast detection of crucial defects and features of devices during manufacturing.

Analytic Modeling of the of J–V Characteristics of Quantum Dot-Based Photovoltaic Cells

An analytic model of [Formula: see text]–[Formula: see text] characteristics of photovoltaic devices based on quantum dot (QD) solids is developed. The model yields the upper estimation of the power conversion efficiency and predicts its extremal dependence on the diffusion length of excitons. The predictive power of our model is approved by the comparison with the experimental data for PbS QD-based solar cells.

Research on Grid-connected PV Power Station Condition Evaluation Technology Based on SCADA and Hierarchical Progression

This paper draw up the conditional evaluation strategy of grid-connected photovoltaic (PV) power generation stations based on the characterization of PV devices, and introduced the conditional evaluation index system includes performance and reliability of PV power generation station. This conditional statement evaluation method is based on both sides of the reliability and performance of PV devices, employ the availability, MRTBF, performance ration and power generation ability as the key evaluation index. In addition, using the operation data recorded by SCADA and recommended threshold values, in order to evaluation the operation conditional statement of grid-connected PV power generation station. Also, this paper proposed the performance degradation analysis method based on the hierarchical progression structure, and achieved the target of fast fixed position of fault PV devices. The firstly established conditional evaluation method is able to comprehensive evaluation the entirely operation statement of PV power generation station. This conditional statement evaluation method promotes the maintenance strategy of grid-connected PV power generation station, and guarantee the safe, stable and efficiency operation of stations. As a result, increase the benefits of operators of PV power generation stations and can be used to guide the PV power engineering.

Simultaneous functional and structural imaging for photovoltaic devices

The functionality of photovoltaic devices (such as, solar cells) is converting photons to electricity. Characterization of photovoltaic devices is essential at production level and during use. Here we put forward a new concept of functional imaging for photovoltaic devices. Based on the concept, we also propose an optical technique that can simultaneously acquire functionality and structure images of a single or multiple photovoltaic devices. The technique is simple, low-cost, effective, and efficient. It requires no mechanic motion and instead structured illumination is adopted for image acquisition. The complementary information provided by the functionality and structure images acquired allows one to better identify any existing and developing faults of photovoltaic devices. What's more, the technique is able to give reliable results with much fewer measurements than image pixels by exploiting the sparsity of functionality and structure images in the Fourier domain. The technique allows not only users to monitor the ‘health condition’ of the utilized devices, but also manufacturers to improve their fabrication conditions. The proposed technique may be applicable for rapid characterization for other semiconductor-based devices.

Ultrahigh-Frequency Heterodyne Lock-In Carrierography for Large-Scale Quantitative Multi-Parameter Imaging of Colloidal Quantum Dot Solar Cells

Ultrahigh-frequency heterodyne lock-in carrierography (UHF-HeLIC) is a new near-IR dynamic photoluminescence (PL) camera-based large-area imaging technique. It is specifically developed for investigating dynamic optoelectronic events that occur at very fast diffusion-wave rates (> = 10 kHz), above which conventional camera imaging cannot be achieved. The nonlinear combination of two-frequency-modulated photogenerated carrier density waves (CDWs) with a 10 Hz beat frequency was used to generate HeLIC images in the UHF range (up to 270 kHz) above the effective CDW recombination rate. Using sequences of these high-frequency images and UHF-HeLIC theory, carrier lifetime, diffusivity, and diffusion and drift length images were reconstructed from colloidal quantum dot solar cells and used for studying the influence of surface and interface trap states on photocarrier transport processes. The new non-destructive UHF-HeLIC imaging methodology shows excellent potential for industrial in-line photovoltaic device characterization, fundamental optoelectronic physical process studies, and various other photoelectronic applications.

Effect of the second chromophore energy gap on photo-induced electron injection in di-chromophoric porphyrin-sensitized solar cells.

This work investigates the effect of the second chromophore energy gap on charge generation in porphyrin-based di-chromophoric dye-sensitized solar cells (DSSCs). Three di-chromophoric porphyrin dyes (PorY, PorO and PorR) containing three organic chromophores with decreasing frontier orbital energy offsets, including a carbazole-triphenylamine chromophore (yellow, Y), a carbazole fused-thiophene chromophore (orange, O) or a carbazole-thiophene benzothiadiazole thiophene chromophore (red, R), were investigated using optical and electrochemical methods, steady-state photoluminescence and photovoltaic device characterization. Energy transfer from the organic chromophore to the porphyrin was suggested in PorY and PorO as the main charge generation mechanism in DSSCs using these di-chromophoric dyes. On the other hand, electron transfer from the photo-excited porphyrin to the organic chromophore as a competing pathway leading to the loss of photocurrent is suggested for PorR-sensitized solar cells. The latter pathway leading to a loss of photocurrent is due to the lower lying lowest unoccupied molecular orbital of the additional organic chromophore (R) and suggests the limitation of the current di-chromophoric approach to increase the overall efficiency of DSSCs.

The role of sulfurization temperature on the morphological, structural and optical properties of electroplated Cu2MnSnS4 absorbers for photovoltaics

In the present work, the effect mechanisms of the sulfurization temperature on the Cu2MnSnS4 (CMTS) absorbers and the photovoltaic characteristics of devices were studied systematically. The results indicate that an increase in sulfurization temperature form 500 °C to 560 °C significantly improves the crystallinity and morphology, lowers the band gap of the CMTS absorbers, and eventually enhances the photovoltaic performance. However, a further increase in the temperature to 590 °C degrades the crystallinity and morphology. By tuning sulfurization temperature, the short current density (Jsc) and power conversion efficiency (PCE) increase over fourfold. When the temperature optimized to 560 °C, the CMTS solar cell shows the highest PCE of 0.91% with Jsc = 7.71 mA·cm−2, Voc = 320 mV and FF = 37%.

Laser-assisted dry, wet texturing and phase transformation of flexible polyethylene terephthalate substrate revealed by Raman and ultraviolet-visible spectroscopic studies

A systematic understanding of laser-induced texturing and its influence on the local structural change in polyethylene terephthalate (PET) substrate offers enhanced performance characteristics of photovoltaic devices. The formation of multiple phases in flexible PET substrate using selective processing by means of laser-assisted heat input reveals enhanced ultraviolet-visible (UV-Vis) absorption. The authors investigate the characteristics of multiple phases formed during the interaction of the laser pulse on the PET substrate processed under dry and wet environments. It is observed that the laser beam profile is replicated on the substrate during wet environment. Moreover, the heat gradient of laser beam have induced various indexed crystalline phases as revealed by Raman spectroscopy as well as their optical characteristics of replicated profile on PET substrate is quantified using UV-Vis absorption spectroscopy. Furthermore, a redshift in the absorption measured at the center of the projected beam profile is attributed to the higher degree of ordered crystalline phase as compared to other graded phases inside the trench. These findings of phase gradients and their influence on optical properties of laser-induced texturing would be useful for laser-based rapid texturing for flexible photovoltaics.

A Biopolymer Heparin Sodium Interlayer Anchoring TiO2 and MAPbI3 Enhances Trap Passivation and Device Stability in Perovskite Solar Cells.

Traps in the photoactive layer or interface can critically influence photovoltaic device characteristics and stabilities. Here, traps passivation and retardation on device degradation for methylammonium lead trihalide (MAPbI3 ) perovskite solar cells enabled by a biopolymer heparin sodium (HS) interfacial layer is investigated. The incorporated HS boosts the power conversion efficiency from 17.2 to 20.1% with suppressed hysteresis and Shockley-Read-Hall recombination, which originates primarily from the passivation of traps near the interface between the perovskites and the TiO2 cathode. The incorporation of an HS interfacial layer also leads to a considerable retardation of device degradation, by which 85% of the initial performance is maintained after 70 d storage in ambient environment. Aided by density functional theory calculations, it is found that the passivation of MAPbI3 and TiO2 surfaces by HS occurs through the interactions of the functional groups (COO- , SO3- , or Na+ ) in HS with undersaturated Pb and I ions in MAPbI3 and Ti4+ in TiO2 . This work demonstrates a highly viable and facile interface strategy using biomaterials to afford high-performance and stable perovskite solar cells.

Rapid Photovoltaic Device Characterization through Bayesian Parameter Estimation

Summary In photovoltaic (PV) materials development, the complex relationship between device performance and underlying materials parameters obfuscates experimental feedback from current-voltage ( J - V ) characteristics alone. Here, we address this complexity by adding temperature and injection dependence and applying a Bayesian inference approach to extract multiple device-relevant materials parameters simultaneously. Our approach is an order of magnitude faster than the cumulative time of multiple individual spectroscopy techniques, with added advantages of using device-relevant materials stacks and interface conditions. We posit that this approach could be broadly applied to other semiconductor- and energy-device problems of similar complexity, accelerating the pace of experimental research.

Colloidal quantum dot solar cell electrical parameter non-destructive quantitative imaging using high-frequency heterodyne lock-in carrierography and photocarrier radiometry

Colloidal quantum dot (CQD) solar cells with a certified power conversion efficiency of 11.28% were characterized using camera-based heterodyne lock-in carrierography (HeLIC) and photocarrier radiometry (PCR). Carrier lifetime, diffusivity, and diffusion and drift length of a CQD solar cell were imaged in order to investigate carrier transport dynamics, as well as solar cell homogeneity and the effects of Au contacts on carrier transport dynamics. Using room temperature HeLIC imaging which has also been demonstrated using PCR measurements, shorter carrier lifetimes (ca. 0.5μs) were found in Au contact regions that can be attributed to enhanced non-radiative recombinations through trap states at Au/CQD interfaces. This imaging methodology shows strong potential for elucidating the energy loss physics of CQD solar cells and for industrial non-destructive large-area photovoltaic device characterization.

Compressed Sensing Current Mapping Spatial Characterization of Photovoltaic Devices

A new photovoltaic (PV) device current mapping method has been developed, combining the recently introduced compressed sensing (CS) sampling theory with light beam induced current (LBIC) measurements. Instead of a raster scan, compressive sampling is applied using a digital micromirror device. The aim is to significantly reduce the time required to produce a current map, compared to conventional LBIC measurements. This is achieved by acquiring fewer measurements than a full raster scan and by utilizing the fast response of the micromirror device to modulate measurement conditions. The method has been implemented on an optical current mapping setup built at the National Physical Laboratory, U.K. Measurements with two different PV cells are presented in this paper and an analytical description for realization of an optimized CS current mapping system is provided. The experimental results illustrate the feasibility of the method and its potential to significantly reduce measurement time of current mapping of PV devices.