Optimisation of a universal reference cell for the indoor light measurement of solar cells

The massive growth of the Internet of Things (IoT) and the unsustainable maintenance and environmental cost of tens-of-millions of battery changes per day is driving developments of indoor photovoltaic (IPV) technologies. These can harvest energy from indoor artificial light sources to power IoT and wearable devices avoiding the need for battery changes.

Development, commercialisation and volume production of IPV products requires characterisation tools like indoor light simulators to measure and compare device performance. Accurate output of such equipment needs to be confirmed. Until recently the development of IPV has been constrained by a lack of accepted standard performance characterisation methodologies and tools.

This has now been addressed with the recent publication of a new IEC standard document. Ensuring traceable measurements when using light simulators (e.g. Lightricity's LightBox or various bespoke laboratory rigs) requires appropriately calibrated reference devices to maintain traceability.

Lightricity's own IPV technology is uniquely stable and spectrally matched to indoor light spectra making it ideal as the basis of a reference cell. We have already developed and sold an IPV reference cell product which can be used as a reference cell for irradiance calibration for indoor light simulators, or integrated on our modular indoor light simulator product range (LightBox).

Nevertheless, due to the lack of standards for IPV reference cell requirements and calibration methodologies, this product cannot yet be used as a calibrated reference by customers. This proposed project aims to improve the reference cell product to better meet customer needs in a portable, more widely transferrable device design by addressing a series of measurement and methodology challenges.

Doing this requires access to expertise and equipment at the National Physical Laboratory which are beyond Lightricity's own capabilities and are not commercially available.