Executive Summary

Although thin-film photovoltaic (PV) modules have been in production for decades, the
characterization of their performance, both outdoors and under artificial light, remains a topic
of active research. This is because the field contains a diverse set of PV technologies, each of
which has physical differences from conventional crystalline silicon PV. These differences
range from different temperature coefficients to complex short-term or seasonal transients in
performance. This report summarises the nature of these special behaviours and
demonstrates best practices for handling them in the context of several case studies.
The first portion of the report deals with the performance of thin-film PV modules in solar
simulators. Achieving repeatable performance measurements is challenging, even under
artificial light. Stable, spectrally matched reference modules are generally unavailable, which
can lead to errors in the effective illumination level. Some technologies have high capacitance,
leading to problematic dependence of results on the duration of illumination and of the I-V
curve sweep. Modules must be stabilised to avoid the influence of metastabilities on the
results. This is normally done by light exposure or “light soaking” and the report proposes an
approach for improving upon simple light soaking by applying bias….