Search documents

Browse topics

Document details

High Resolution Linearity Measurements of Solar Cells Using Digital Light Processing Projection
G. Koutsourakis, T. Eales, I. Kröger, J.C. Blakesley
New Materials and Concepts for Photovoltaic Devices
Subtopic: Fundamental Studies
Event: 37th European Photovoltaic Solar Energy Conference and Exhibition
Session: 1AO.1.3
ISBN: 3-936338-73-6
0,00 EUR
Document(s): presentation


Although solar cells are rated at Standard Testing Conditions (STC), in reality outdoor irradiance levels are highly variable and STC conditions are rarely met. Thus, it is beneficial to fully characterise the linearity of the photovoltaic (PV) devices. In addition, high accuracy linearity measurements are essential for reference cells, as they ensure the precision of the measured irradiance. This work presents a new technique for linearity measurements of PV devices based on digital light processing (DLP). Instead of using meshes, neutral density filters or a series of similar light sources, a system which utilises a Digital Micromirror Device (DMD) coupled with projection optics and high-power LEDs is used. By creating a series of projections patterns on the device under test with a specific number of bright and dark pixels, linearity measurements can be implemented through a spatial dithering process. Since the dithering process is mechanical, it is expected that any spectral effects for the different dithering levels or electrical non-linearities of the light source are avoided. The developed system can provide thousands of measurement points on the linearity curve of a device in minutes, which is impossible with any currently established methods. Measurements of reference cells with known linearity curves are acquired, measurements are also validated by conventional methods. Results demonstrate that the DLP method provides equal if not better measurement accuracy compared to conventional systems, at significantly higher resolution (points on the linearity curve) and order of magnitude higher measurement speed.