The WCT-120 is a tabletop silicon lifetime and wafer metrology system- suitable for both device research and industrial process control. It uses the quasi-steady-state photoconductance (QSSPC) lifetime measurement method for monitoring multicrystalline wafers- dopant diffusions- and low-lifetime samples. This method complements the use of the transient photoconductance technique that is also standard on this instrument. The QSSPC lifetime measurement also yields the implied open-circuit voltage (versus illumination) curve- which is comparable to an I-V curve at each stage of a solar cell process. The Suns-Voc stage is used for measuring wafers after Al firing- and then again after front-grid firing. This allows the optimization and monitoring of these steps to maintain voltage- obtain good ohmic contacts- and avoid shunting. By either probing the p+ and n+ regions directly or probing the metallization layer (if present)- the illumination-Voc curve can be measured. This curve can be displayed as a Suns-Voc plot or in the form of a standard photovoltaic curve which can be used to characterize shunting. The entire curve is measured at open circuit- so it is free from the effects of series resistance.
Instrument specifications are provided on labs portal https://labs.masdar.ac.ae