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Microcracks at the device level in bulk solar cells are the current subject of substantial research by the photovoltaic (PV) industry. This review paper addresses nondestructive testing techniques that are used to detect microfacial and subfacial cracks. In this paper, we mainly focused on mono-and polycrystalline silicon PV devices and the root causes of the cracks in solar cells are described. We have categorized these cracks based on size and location in the wafer. The impact of the microcracks on electrical and mechanical performance of silicon solar cells is reviewed. For the first time, we have used the multi-attribute decision-making method to evaluate the different inspection tools that are available on the market. The decision-making tool is based on the analytical hierarchy process and our approach enables the ranking of the inspection tools for PV production stages, which have conflicting objectives and multi-attribute constraints.

SYNOPSISThe ultraviolet spectra of pure and lead salt-poly(viny1 alcohol) (PVA) composite films were studied at room temperature. Blending of PVA with lead acetate and lead nitrate cause a considerable change in the UV spectrum, indicating electronic structure modifications. The complex permittivity (c*) and the complex electric modulus ( M * ) of the pure PVA and the PVA-based composite films were investigated between 300 and 400 K in the 100 Hz-100 kHz frequency range. The frequency dependence of the permittivity is influenced by the space-charge polarization. The interfacial polarization is manifested a t high temperature and becomes important only above the PVA glass transition temperature and below 1 kHz. Dielectric properties of PVA-lead nitrate composite revealed that the salt is complexed with PVA through hydrogen bonding.

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A novel hybrid solar concentrated photovoltaic thermal (PV/T) collector is designed, simulated, and tested. The PV/T system uses a parabolic trough to focus sunlight towards a nonimaging compound parabolic concentrator (CPC) that is formed of single junction Gallium Arsenide (GaAs) solar cells to simultaneously generate electricity and high temperature thermal power. The GaAs cells generate electricity from high energy photons and reflect low energy photons towards the high temperature absorber, thus maximizing the exergy output of the system. The two-stage design also allows the thermal absorber to reach a geometric concentration ratio of ~60X, which is significantly higher than other PV/T systems and enables the absorber to reach high temperatures even under partial utilization of the solar spectrum. The modelled exergy efficiency with a thermal absorber operating at 500 °C is 37%. In the experimental setup, the maximum outlet temperature reached was 365 ºC with a thermal efficiency of around 37%. The direct solar to electric efficiency from the GaAs cells was 8%. This design is capable of producing electricity directly along with high temperature thermal energy that can be stored for dispatchable electricity production and has the potential to significantly improve the exergy efficiency of parabolic troughs plants.

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