New instrument measures organic solar cell thickness in real time
Layer uniformity and thickness are critical parameters defining solar cell performance. Conventional methods typically monitor layer thickness after the deposition process. THIME (Thinfilm measurements on organic photovoltaic layers) project's innovative solution offers an alternative to the currently used thickness metrology instruments or online single-point systems. The newly developed quality control system provides real-time measurements across the full web width, thereby obtaining a thickness map that has not been used in the printing industry to date. The tool can measure layer thicknesses down to 500 nm. Operation is based on two different optical techniques: optical interferometry and spectroscopic ellipsometry. The system's versatility and the possibility to adapt it to different materials and substrates with proper calibration and modelling are important features of THIME's solution. Sophisticated software allows the operator to analyse the system output through a graphic interface and record measurements of a printed web's thickness during printing for post-processing analysis. The THIME system was tested in three different industrial installations and proved to fulfil the operators' requirements. It was installed after the oven step in the printing machine, thereby allowing measurement of the dry thickness, which is unknown to most operators in solar cell printing. Real-time monitoring of the coated web properties enhances control of the printing process while helping to reduce faulty products and material waste. Project members demonstrated that the project's system provides more information with the same level of quality than conventional measurement instruments such as mechanical profilometers. This facilitates closed-loop control of the printing process, allowing a fully optimised production line. Setting the stage for cost-effective technology for high-volume manufacturing, printed large-area organic photovoltaics has started enjoying a lot of buzz in the solar cell industry. Commercialisation of the THIME system is expected to boost European leadership in this field. Watch the project’s video here.
Keywords
Solar cell, real time, thickness measurement, thin films, large-area organic photovoltaics, layer thickness, roll-to-roll, hyperspectral, ellipsometry
