Overview
IEC TS 63109:2022 “Photovoltaic (PV) modules and cells - Measurement of diode ideality factor by quantitative analysis of electroluminescence images” specifies a non‑contact method to measure the diode ideality factor (n) of crystalline‑silicon photovoltaic cells and modules using quantitative analysis of electroluminescence (EL) images. The Technical Specification defines n (the inverse of the incremental slope of ln(I) vs. V, normalized by thermal voltage), explains its relation to key performance metrics such as fill factor (FF), open‑circuit voltage (Voc) and short‑circuit current (Isc), and gives procedures for capturing and analysing EL intensity to derive n values.
Key topics and requirements
- Scope and applicability: Applicable to crystalline silicon PV cells and modules only; provides measurement and reporting requirements.
- Definition of diode ideality factor (n): Formal definition linked to dark I–V behaviour and thermal voltage.
- Quantitative EL analysis procedures: Guidance on EL image capturing, camera calibration, sample preparation and controlled injection current to obtain EL intensity vs. current data.
- Data analysis to derive n: Use of EL intensity dependence on injection current to infer the diode ideality factor (normative derivation in Annex A).
- Measurement reporting: Required content for reproducible results and traceability.
- Informative annexes: Examples of measurements (Annex B) and use of a practical single diode model to relate n to module output performance (Annex C).
- Referenced documents: Normative links to IEC TS 60904‑13 (EL of PV modules) and IEC TS 61836 (terms and symbols).
Practical applications
- Quality control and R&D: Manufacturers can monitor pn‑junction electronic quality during development and production using EL‑derived n as an indicator of junction recombination or transport mechanisms.
- Field diagnostics and asset management: Power producers and O&M teams can non‑destructively screen installed modules for degradation (e.g., increased recombination, PID, aging) without disassembling strings or isolating individual cells.
- Second‑hand module valuation and reuse: Buyers and refurbishers can assess remaining electronic performance of used modules beyond visual EL inspection by quantifying n.
- Research and failure analysis: Labs and researchers can correlate EL‑derived n with I–V characteristics and microscopic defects to study degradation mechanisms.
Who should use this standard
- PV manufacturers and module test engineers
- O&M and asset managers in solar power plants
- Photovoltaic test laboratories and certification bodies
- Researchers studying PV degradation and non‑destructive evaluation
Related standards
- IEC TS 60904‑13 - Electroluminescence of photovoltaic modules (normative reference)
- IEC TS 61836 - Solar photovoltaic energy systems - Terms, definitions and symbols
IEC TS 63109:2022 enables a practical, non‑contact, image‑based approach to quantify diode behaviour in PV cells and modules, making EL imaging a more quantitative diagnostic tool for performance assessment and lifecycle management.