We describe a simple and low-cost wet-chemical route for the synthesis of ZnO nanowire/nanoparticle composite electrodes. The integration of such nanocomposite photoanodes in dye-sensitized solar ...cells (DSSCs) leads to much better photovoltaic properties than for bare nanowire or nanoparticle ensembles with a photoconversion efficiency as high as 4.7%. Importantly, beneficial effects of thermal heat treatments are investigated in terms of ZnO nanoparticle formation and DSSC photovoltaic properties. In particular, we reveal the presence of a zinc oxoacetate intermediate phase from 120 °C, which drastically reduces the electron leakages at the ZnO/dye/electrolyte interface, while retaining a large specific surface area and a relatively good electron injection efficiency.
Photoluminescence (PL) imaging is a powerful inspection technique that has found widespread applications in photovoltaic research and in high volume production. Recently, the use of this technology ...has been expanded to include the inspection of field-deployed solar modules under full sunlight conditions. However, the methods demonstrated so far require electrical switching of the tested modules between two electrical operating points, the PL signal given as the difference between two near-infrared images. In the current work we propose a simplified approach in which PL images are taken without the need for toggling between two operating points. The principles of the technique, which has significant practical advantages, are discussed and experimental proof of concept data are provided.
Kesterite-based Cu
ZnSn(S,Se)
semiconductors are emerging as promising materials for low-cost, environment-benign, and high-efficiency thin-film photovoltaics. However, the current state-of-the-art ...Cu
ZnSn(S,Se)
devices suffer from cation-disordering defects and defect clusters, which generally result in severe potential fluctuation, low minority carrier lifetime, and ultimately unsatisfactory performance. Herein, critical growth conditions are reported for obtaining high-quality Cu
ZnSnSe
absorber layers with the formation of detrimental intrinsic defects largely suppressed. By controlling the oxidation states of cations and modifying the local chemical composition, the local chemical environment is essentially modified during the synthesis of kesterite phase, thereby effectively suppressing detrimental intrinsic defects and activating desirable shallow acceptor Cu vacancies. Consequently, a confirmed 12.5% efficiency is demonstrated with a high V
of 491 mV, which is the new record efficiency of pure-selenide Cu
ZnSnSe
cells with lowest V
deficit in the kesterite family by E
/q-Voc. These encouraging results demonstrate an essential route to overcome the long-standing challenge of defect control in kesterite semiconductors, which may also be generally applicable to other multinary compound semiconductors.
All PV modules must maintain their performance for years once deployed in the field. Understanding the impact of new processing and materials on the long-term reliability of panels is thus crucial. ...This paper demonstrates the use of line scan photoluminescence (PL) imaging to study the impact of heat stress on two types of Cu(In,Ga)(S,Se)2 (CIGS) modules. The spatial information provided by the images, which allows separation of recombination and series resistance effects, is shown to provide insight into the root causes of degradation in high efficiency thin film modules.
Spectroscopic ellipsometry is applied to investigate the effect of Cu/Zn disorder in a Cu2ZnSnSe4 crystal on the optical transitions. We observe that the degree of order has an impact not only on the ...first optical transition E0 at the gamma point, which is the commonly discussed direct band gap in kesterites. It also varies the further optical transition E1 away from the gamma point. While E0 shows an increasing trend with higher degree of order, the transition E1 shows an opposite behavior, indicating a fundamental impact of disorder on the shape of the electronic bands of kesterite material.
•SE was used to investigate the effect of different degrees of Cu-Zn order in Cu2ZnSnSe4 crystal on the optical transitions.•Cu/Zn ordering not only effects the fundamental band gap E0, it also effects the further optical transition E1.•While E0 is increasing with increasing Cu/Zn ordering level in Cu2ZnSnSe4 crystal, E1 shows an opposite behavior.•Relative energy differences between ordered and disordered state in this study are in good agreement with previous reports.
Recent improvements in Cu(In,Ga)Se 2 (CIGS) solar cells have made use of thinner CdS layers. The homogeneity of this layer is critical to maintain a high-quality CdS/CIGS heterojunction. We present ...an imaging method based on photoluminescence (PL) intensity ratios using UV and red excitation. UV light is partially absorbed by the CdS, while it is transparent to red photons. Hence, inhomogeneity in the CdS layer thickness produces different UV excitation of the underneath CIGS layer, while the red excitation is uniform, leading to contrast in the PL image ratio. The method is highly sensitive to detect defects or pinholes in the CdS layer and can be used as a rapid method for CdS deposition quality control.
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