Nondestructive inspection, testing and evaluation for Si-based, thin film and multi junction solar cells: An overview

Solar energy is one of the fastest growing renewable energy resources. It is extremely important to improve the reliability and availability of solar energy systems and to further reduce the operation and maintenance (O & M) cost. Solar cells and modules are considered as one of the most critical components in solar energy system because they convert solar energy into electricity. Flaws and damages are inevitable during either the fabrication or the service life of a solar cell or module. Thus, nondestructive inspection, testing and evaluation (NDI, NDT & NDE) for solar cells and modules are required in both manufacturing quality control and in-service inspection. In this work, a fully, in-depth and comprehensive review of NDT & E techniques for Si-based, thin film and multi-junction solar is reported based on an orderly and concise literature survey. Firstly, the developments and case comparison studies of electromagnetic, sonic and ultrasonic, optical, thermal, near-infrared, terahertz and mechanical test NDT & E for Si-based solar cells especially in the last three years are reviewed in detail. Next, the developments of NDT & E methods for film and multi-junction solar cells are also reviewed. After that, the strengths and limitations of these NDI and NDT techniques are concluded through comparison studies. Analytic hierarchy process (AHP) is used to compare 7 kinds of NDT methods which include photoluminescence (PL), electroluminescence (EL), illuminated lock-in thermography (ILIT), dark lock-in thermography (DLIT), resonance ultrasonic vibration (RUV), optical NDT and lamb wave air coupled ultrasonic testing (LAV-UT). In addition, the development tendencies for solar cell and related NDT & E are predicted. This work will serve as a guide for performance testing, failure analysis, quality control and health monitoring of Si-based cells, thin film and multi-junction solar cells and play an important role in solar energy safety control and cost saving.