IEC TS 60904-1-2:2019

Overview

IEC TS 60904-1-2:2019 specifies procedures for measuring the current‑voltage (I‑V) characteristics of bifacial photovoltaic (PV) devices under natural or simulated sunlight. It extends the general I‑V measurement principles of IEC 60904‑1 by defining the additional requirements needed when both the front and rear faces of a PV cell, sub‑assembly or complete module contribute to power generation. The Technical Specification also covers cases where devices are intended for concentrated irradiation if measured without concentration optics and corrected to a direct‑normal reference spectrum.

Key topics and technical requirements

• Scope of application: single cells, cell sub‑assemblies, and full PV modules that are bifacial.
• Measurement environments: natural sunlight and solar simulator testing (single‑side and double‑side illumination).
• Apparatus requirements: solar simulators with adjustable irradiance, non‑irradiated background control and background compensation to avoid measurement artifacts.
• Bifaciality metrics: definition and determination of bifaciality coefficients for ISC, VOC and Pmax (ratio of rear to front characteristics, typically at STC).
• Rear irradiance driven power gain (BiFi): methodology to quantify power gain per unit rear irradiance (expressed in W/(W·m‑2)) and procedures for outdoor and indoor measurements to derive BiFi.
• I‑V characterisation procedures: recommended sequences for measuring reference bifacial devices, using reference devices for comparative measurements, and deriving corrected Pmax values (e.g., Pmax,BiFi100/200).
• Reporting: standardized reporting items to ensure reproducibility and meaningful comparison of bifacial device performance.

Applications and who should use it

• PV test laboratories and accredited calibration facilities - for standardised I‑V testing and traceable performance data for bifacial modules.
• Module manufacturers and R&D teams - to characterise bifaciality, validate product claims, and optimise cell/module designs.
• Certification and conformity bodies - for consistent test methods when evaluating bifacial PV products.
• System designers and performance modelers - to translate measured bifacial metrics (BiFi, bifaciality) into expected field energy gains considering albedo and mounting.
• Component suppliers (encapsulants, glass) - for understanding rear‑side optical impacts on bifacial performance.

Related standards

Key normative references and complementary documents include:

• IEC 60904‑1, IEC 60904‑2, IEC 60904‑3, IEC 60904‑4, IEC 60904‑5, IEC 60904‑7, IEC 60904‑8, IEC 60904‑9
• IEC 60891 (temperature & irradiance corrections)
• IEC TS 61836 (terms and symbols), IEC TS 62446‑3, IEC 62788‑1‑4

IEC TS 60904‑1‑2:2019 is essential for anyone needing repeatable, comparable I‑V data for bifacial PV devices and for quantifying the additional power contribution from rear‑side irradiance.