Photovoltaic Characterization Research Articles

Optimization of absorber layer for band gap energy moderation of nanostructured SnS thin films

In the present work, band gap energy moderated nanostructured Sn1−xZnxS thin film solar cell devices are investigated in details in order to optimize the number of their layers, which can enhance their efficiency. Sn1−xZnxS nanostructures were synthesized by simple and cost-effective co-precipitation method and were primarily characterized for the study of their structural and phase purification as well as morphological and optical properties. Structural results confirmed the formation of polycrystalline orthorhombic and hexagonal phase of SnS and ZnS nanostructures, respectively. Morphological studies showed that increasing the Zn concentrations changed the morphology of samples from the rod- to spherical- and hexagonal-like particles. Electrical characterization also presented the highest carrier concentration and conductivity conversion in the Sn1/2Zn1/2S sample. Photovoltaic devices were deposited using the ethyl cellulose as a green binder on the transparent substrates and TiO2 buffer layers. Photovoltaic characterization showed that a sample moderated from low-to-high values of band gap energy and with four layers has better efficiency (3.17%) because of factors such as having a wide broadband range of band gap energy in absorber layer, increase in carrier lifetimes, presence of minor carriers in output current, and an increase in carrier concentration of the moderated layers. This paper also investigates and compares our results with the literature and gives some suggestions for coping with the problems involved in having a high number of layers in the fabricated devices.

Photovoltaic Properties of Perovskite Solar Cells According to TiO2 Particle Size

The photovoltaic properties of TiO2 used for the electron transport layer in perovskite solar cells(PSCs) are compared according to the particle size. The PSCs are fabricated and prepared by employing 20 nm and 30 nm TiO2 as well as a 1:1 mixture of these particles. To analyze the microstructure and pores of each TiO2 layer, a field emission scanning electron microscope and the Brunauer–Emmett–Teller(BET) method are used. The absorbance and photovoltaic characteristic of the PSC device are examined over time using ultraviolet-visible-near-infrared spectroscopy and a solar simulator. The microstructural analysis shows that the TiO2 shape and layer thicknesses are all similar, and the BET analysis results demonstrate that the size of TiO2 and in surface pore size is very small. The results of the photovoltaic characterization show that the mean absorbance is similar, in a range of about 400-800 nm. However, the device employing 30 nm TiO2 demonstrates the highest energy conversion efficiency(ECE) of 15.07 %. Furthermore, it is determined that all the ECEs decrease over time for the devices employing the respective types of TiO2. Such differences in ECE based on particle size are due to differences in fill factor, which changes because of changes in interfacial resistance during electron movement owing to differences in the TiO2 particle size, which is explained by a one-dimensional model of the electron path through various TiO2 particles.

Combination of high and low temperature carbon pastes to fabricate counter electrode of perovskite solar cell

The high cost, complicated synthesis and coating process of organic hole-transporting materials such as Spiro-OMeTAD, as well as their negative effect on the stability of the device, are the principal impediments for the commercialization of perovskite solar cells. To overcome these obstacles, the attentions increased toward developing hole-transporting material-free perovskite solar cells. In the present work, perovskite solar cell was fabricated by combining two kinds of carbon counter electrodes, including one layer of mesoscopic carbon paste mixed with terpineol and covered by one layer of carbon paste mixed in ethyl-acetate. The crucial difference between two layers lies in their sintering temperature. Also, different thicknesses for the first carbon layer, as well as the effect of dipping time in methyl ammonium iodide were examined. Following the photovoltaic characterization, the achieved optimized efficiency of the hole-conductor-free perovskite solar cell was 11.82 ± 2.07%. Besides, the thickness of the carbon, layer that affects the conductivity and fill factor, and the appropriate contact between perovskite and carbon counter electrode are considered here as two important parameters in optimizing the efficiency of hole-conductor-free perovskite solar cell.

Optical Characterization and Photovoltaic Performance Evaluation of GaAs p-i-n Solar Cells with Various Metal Grid Spacings

GaAs p-i-n solar cells are studied using electroreflectance (ER) spectroscopy, light beam induced current (LBIC) mapping and photovoltaic characterization. Using ER measurements, the electric field across the pn junction of a wafer can be evaluated, showing 167 kV/cm and 275 kV/cm in the built-in condition and at −3 V reverse bias, respectively. In order to understand the effect of the interval between metal grids on the device’s solar performance, we performed LBIC mapping and solar illumination on samples of different grid spacings. We found that the integrated photocurrent intensity of LBIC mapping shows a consistent trend with the solar performance of the devices with various metal grid spacings. For the wafer used in this study, the optimal grid spacing was found to be around 300 μm. Our results clearly show the importance of the metal grid pattern in achieving high-efficiency solar cells.

Tuning the optoelectronic properties of vinylene linked perylenediimide dimer by ring annulation at the inside or outside bay positions for fullerene-free organic solar cells

Abstract Among various perylenediimide (PDI)-based small molecular non-fullerene acceptors (NFAs), PDI dimer can effectively avoid the excessive aggregation of single PDI and improve the photovoltaic performance. However, the twist of perylene core in PDI dimer will destroy the effective conjugation. Thus, ring annulation of PDI dimer is a feasible method to balance the film quality and electron transport, but the systematic study has attracted few attentions. Herein, we choose a simple vinylene linked PDI dimer, V-PDI2, and then conduct further studies on the structure-property-performance relationship of four kinds of derived fused-PDI dimers, namely V-TDI2, V-FDI2, V-PDIS2 and V-PDISe2 respectively. The former two are incorporated thianaphthene and benzofuran at the inside bay positions, and the latter two are fused thiophene and selenophene at the outside bay positions, respectively. Theoretical calculations reveal the inside- and outside-fused structures largely affect the skeleton configuration, the former two tend to be planar structure and the latter two maintain the distorted backbone. The photovoltaic characterizations show that the inside-fused PDI dimers offer high open circuit voltage (VOC), while the outside-fused PDI dimers afford large short-circuit current density (JSC). This variation tendency results from the reasonably tunable energy levels, light absorption, molecular crystallinity and film morphology. As a result, PBDB-T:V-PDISe2 device exhibits the highest power conversion efficiency (PCE) of 6.51%, and PBDB-T:V-FDI2 device realizes the highest VOC of 1.00 V. This contribution indicates that annulation of PDI dimers in outside or inside bay regions is a feasible method to modulate the properties of PDI-based non-fullerene acceptors.

Conductive glass free carbon nanotube micro yarn based perovskite solar cells

Perovskite solar cells (PSCs) have emerged as a promising photovoltaic technology on the lab scale due to their high power conversion efficiency, simple device fabrication, all solid-state structure and the possibility to integrate traditional devices into fiber format. In this work, a three-dimensional (3D) perovskite solar cell is demonstrated using functionalized carbon nanotube (CNT) yarn as both the cathode and anode material. TiO2 and 2,2,7,-7-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) are used as the electron transporting and hole transporting material respectively. The TiO2 oxide layer is deposited on the top of the twisted carbon nanotube yarn and annealed with TiCl4 to generate the uniform electron transport layer. A dip coating process is employed to produce a uniform perovskite layer on top of the TiO2 oxide layer. Platinized carbon nanotube yarn is wrapped around on the top of the hole transporting layer and serves as the counter electrode. The photovoltaic characterization of the prepared cells was carried out at different cell lengths. Under AM 1.5 (100 mW cm−2) illumination it shows an enhanced power conversion efficiency (PCE) with a high open current voltage (VOC) of 0.825 V. This three-dimensional all solid-state perovskite solar cell shows a promising prospect in portable and wearable textile electronics.

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.

A review of crystalline silicon bifacial photovoltaic performance characterisation and simulation

This paper presents a review on crystalline silicon bifacial PV performance characterisation and simulation to facilitate new research developments for bifacial PV technology and implementation in the global market.

Correction: A review of crystalline silicon bifacial photovoltaic performance characterisation and simulation

Correction for ‘A review of crystalline silicon bifacial photovoltaic performance characterisation and simulation’ by Tian Shen Liang et al., Energy Environ. Sci., 2019, DOI: 10.1039/c8ee02184h.

Photophysical and Photovoltaic Characterization of Flourene-Anthracene-Benzothiadiazole Based Donor–Acceptor Type Copolymers for Bulk Heterojunction Polymer Solar Cells

Photophysical and Photovoltaic Characterization of Flourene-Anthracene-Benzothiadiazole Based Donor–Acceptor Type Copolymers for Bulk Heterojunction Polymer Solar Cells

Comparative Studies on the Efficiency, Reproducibility and Stability of Perovskite Solar Cells

Abstract In literature, many studies based on planar inverted structure using either CH3NH3PbI3 and CH3NH3PbI3-xClx perovskite absorbers have reported as high-efficiency solid-state perovskite solar cells. This study includes the comparison of photovoltaic characterizations, reproducibility and stability results of solar cells fabricated by using CH3NH3PbI3 and CH3NH3PbI3-xClx perovskite compounds. Herein, the results showed that CH3NH3PbI3 perovskite solar cells gave a lower photovoltaic performance as-fabricated when compared with CH3NH3PbI3-xClx perovskite solar cells. However, after 24 hours, CH3NH3PbI3 perovskite compound showed a higher photovoltaic performance and better time stability in inert atmosphere and more reproducible results

Module Temperature Dispersion Within a Large PV Array: Observations at the Amareleja PV Plant

In-field photovoltaic (PV) module and array characterization is becoming increasingly important within the particular framework of quality assurance procedures at large commercial PV plants. In this context, the correct measurement of the module temperature is critical in order to reduce uncertainty and increase repeatability of results. In the case of large PV array characterization, the measurement provided by the sensors may not be representative of the PV array as a whole given the great diversity of operating conditions occurring throughout its surface area. Spatial temperature differences within a PV array of less than 5 K are typically considered in practice. However, the temperature differences observed at a commercial PV plant in Amareleja (Portugal) are more than twice those typically assumed. Such high differences may considerably increase the uncertainty in the determination of the PV array operating temperature and, hence, in its standard test conditions power characterization. This paper quantifies the uncertainty associated with the in-field measurement of the operating temperature of large PV arrays and their individual PV modules as a function of the type, number, and location of the temperature sensors used. Furthermore, the incident irradiance and particular wind speed conditions over the PV array have been clearly identified as the main causes of these temperature differences, showing that the optimum conditions to perform the PV array characterization do not correspond to low wind speed conditions, as recommended by many authors.

A thiolate/disulfide liquid crystalline electrolyte for dye-sensitized solar cells: Promotion of the Grotthuss-type charge transport through lamellar nanostructures

Smectic 1-dodecyl-3-methyl-1H-imidazol-3-ium 1-methyl-1H-tetrazole-5thiolate ([C12MIm][T]) has been prepared for dye-sensitized solar cells (DSSCs). The electrolyte consisting of [C12MIm][T] and di-5-(1-methyltetrazole) disulfide (T2) with mole ratio 2:1 exhibited smectic A (SA) liquid crystal phase over a temperature range from 12.5–75.5 °C. A bilayer nanostructure formed in the SA phase and the T−/T2 redox couple was intercalated between the smectic layers. Photovoltaic characterization revealed that the power conversion efficiency of the smectic T−/T2 DSSC increased with the increase in temperature and reached 4.1% at 70 °C under simulated AM1.5G solar light. Regression analysis of temperature dependent charge diffusion coefficients and viscosities suggested that the charge transport in the T−/T2 electrolyte was dominated by the Grotthuss-type exchange reaction. The lamellar nanostructure of T−/T2 promoted the Grotthuss-type charge transport and improved the DSSC performance. The ordered arrangement of the redox couple offers an effective way to enhance the charge transport for the DSSC electrolytes unfavorable for physical ion diffusion.

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.

Semi-Transparent Energy-Harvesting Solar Concentrator Windows Employing Infrared Transmission-Enhanced Glass and Large-Area Microstructured Diffractive Elements

We report on the study of energy-harvesting performance in medium-size (400 cm2) glass-based semitransparent solar concentrators employing edge-mounted photovoltaic modules. Systems using several different types of glazing system architecture and containing embedded diffractive structures are prepared and characterized. The technological approaches to the rapid manufacture of large-area diffractive elements suitable for use in solar window-type concentrators are described. These elements enable the internal deflection and partial trapping of light inside glass-based concentrator windows. We focus on uncovering the potential of pattern-transfer polymer-based soft lithography for enabling both the improved photon collection probability at solar cell surfaces, and the up-scaling of semitransparent solar window dimensions. Results of photovoltaic characterization of several solar concentrators employing different internal glazing-system structure and diffractive elements produced using different technologies are reported and discussed.

High isotropic dispiro structure hole transporting materials for planar perovskite solar cells

Abstract Two novel fluorene-based hole transporting materials (HTMs) were synthesized to be used in perovskite solar cells (PSCs). C102 was designed based on C101 by simply linking the two carbon–carbon single bonds to compose a “dispiro” structure. Their typically similar structures cause them sharing almost the same energy levels. However, their photovoltaic performances are quite different due to the small variations. The PSC that contained the “dispiro” structure, C102, reached a power conversion efficiency (PCE) of 17.4%, while the device contained C101, obtained a lower PCE of 15.5%. Electrochemical properties and Photovoltaic characterization of the two materials have been investigated to explain the result. It is shown that C102 has a stronger ability to transport holes and resist the charge recombination. Thus, the dispiro structure should be more appropriate being used as HTM in PSCs.

Short-period fluctuation and spatial distribution of solar irradiance under clouds

Recently, outdoor photovoltaic (PV) module performance characterizations have been carried out mainly for testing installed PV modules. For high-accuracy outdoor measurement, solar irradiance with stability in time and uniformity in space are required. Short-period temporal instability and spatial nonuniformity of solar irradiance are observed using a series of PV module sensors (PVMSs). The speed and direction of cloud shadows moving on PVMSs are evaluated from the fluctuations of irradiance detected by several PVMSs. On the basis of cloud distribution, weather conditions are classified into four types, and the characteristics of solar irradiance fluctuations are examined for each type. The irradiance changes quickly under cumulous clouds. On the other hand, the irradiance becomes weak, but its short-period fluctuations are not evident under layered clouds. The amplitude of irradiance fluctuations reaches 70% of clear-day irradiance at noon in this observation. The spatial nonuniformity evaluated on the basis of the instantaneous difference in irradiance intensity between two PVMSs also reaches 1.8%/m of clear-day irradiance.

Filtering method of detecting solar irradiance conditions for photovoltaic module performance characterization under unstable and nonuniform irradiance

The temporal instability and spatial nonuniformity of solar irradiance, and their relationship are analyzed by field observations, and a method of detecting the events in which irradiance is stable and uniform is proposed for outdoor photovoltaic (PV) module performance characterizations. The relationships of instability and nonuniformity of irradiance with measurement conditions are discussed, e.g., a long measurement time worsens instability. When events are observed with repeated measurements under certain conditions and selected under the condition that the instability is low afterwards, the nonuniformity of the selected events is low. This means that for measuring and detecting uniform events well, two sensors are required, but they can also be detected with a single sensor by repeated measurements and selecting with instability. This suggests that repeated measurements may be a filtering method for finding stable and uniform events, which is required for high-accuracy outdoor PV module performance characterizations.

Chemical state of chlorine in perovskite solar cell and its effect on the photovoltaic performance

Inorganic–organic hybrid perovskite solar cells have become of interest due to their high solar-to-electric power conversion efficiency and low fabrication costs. Recently, it is reported that chlorine doping is an effective means of improving the conversion efficiency and stability of these cells. However, the role played by chlorine and the chemical state of chlorine in the MAPbI3−xClx perovskite is still the subject of much debate. In the present work, we fabricate Cl-containing perovskite films by spin coating a mixed solution of CH3NH3Cl and CH3NH3I on PbI2 films in air. The chemical state of Cl in these films is investigated by X-ray diffraction and X-ray photoelectron spectroscopy. It is found that the Cl is present in different chemical states depending on the concentration of CH3NH3Cl used in the original synthesis. XPS depth profile results demonstrate that Cl is present throughout the samples rather than solely at the perovskite/TiO2 interface as has been reported previously. However, the Cl located at the interface is more stable during thermal treatment of the films. Photovoltaic characterization reveals that strong relationship between the chemical state of chlorine and photovoltaic performance exists.

Optical, spectral and photovoltaic characterization of natural dyes extracted from leaves of Peltophorum pterocarpum and Acalypha amentacea used as sensitizers for ZnO based dye sensitized solar cells

The ZnO nanorods were synthesized using hydrothermal method. The morphologies, crystalline nature and optical properties of the synthesized ZnO nanorods were characterized by X-ray diffractometer, High-resolution scanning electron microscopy [HRSEM], and UV–Vis absorption spectroscopic studies. A thin layer of ZnO nanorods were spread on transparent conducting FTO coated glass plate using Doctor Blade method. Natural dyes extracted from Peltophorum pterocarpum and Acalypha amentacea leaves with solvents such as water and ethanol were used as sensitizers to fabricate dye sensitized solar cells (DSSCs). The extracted dyes were characterized by Fourier transform infrared (FTIR) and UV–Visible absorption spectroscopy. The FTIR confirms the presence of anthocyanin, carotene and chlorophyll molecules in the dye extracts. The influence on the different parameters such as open circuit voltage (VOC) short circuit current (JSC), fill factor (FF), and power conversion efficiency (η) of the dye sensitized solar cells (DSSCs) were analyzed. The ZnO nanorods provide high specific surface area for dye adsorption and the pathway is efficient for electron transportation.