Apparatus for Optimizing Photovoltaic Solar Manufacturing Efficiency through Real-Time Process Feedback and Spectral Binning of Cells

Proposed is the development of a non-contact spectral response (Quantum Efficiency) system capable of monitoring critical process parameters in the solar manufacturing line. The development will leverage Tau Science Corporations extensive experience in photovoltaic metrology and its proprietary FlashQE product line. FlashQE is an LED-based, spectral response system capable of measuring the quantum efficiency (QE) of a photovoltaic solar cell in just 1 second (compared to 5-10 minutes for a conventional QE system). Quantum efficiency provides fundamental information about the performance and characteristics of the cell such as band gap, defectivity, and coating quality. It is of particular interest for thin film technologies, proving stoichiometric information about the mix of materials deposited to build the cell. FlashQE is fast enough to sample at the rate of a modern photovoltaic manufacturing line and was developed with that purpose in mind. However, in its current configuration, the system requires that electrical contact be made with the cell, thereby limiting its use to end-of-line test when the cell has been fully formed. For maximum utility the system could be modified through the development of a non-contact current sensing probe to provide real-time, fundamental information about the solar cell in early in the manufacturing process. These data can be leveraged into improvements in the manufacturing line efficiency as an input to short-loop process control, with the sensor positioned directly after each deposition step. Such information, not currently available to manufacturer, would allow optimization of the line in real-time using the data to identify excursions based on predefined control limits. This would represent a tremendous improvement in the time-to-data for process control by providing real-time feedback rather than waiting until end-of-line to send samples for analysis. Waiting twelve hours or more to evaluate the efficacy of a process step makes it difficult to keep deposition processes within a predefined process window, and leads to larger drift in critical parameters such as film composition. This Phase I proposal seeks funding to develop a proof-of-concept prototype of a non-contact, spectral response measurement system capable of operating within the cost, throughput, and facilities constraints of a modern photovoltaic cell manufacturing line. The development will involve modification of an existing Tau Science product from being contact (requiring leads to fly to the cell) to being non-contact (using a capacitive probe or similar sensing schema). Basic characterization and noise studies will be conducted using the prototype and industry input will be sought through Tau Sciences customer contacts.