Photocurrent and electroluminescence mapping system for optoelectronic device characterization using a PC sound card for data acquisition

A compact photocurrent and electroluminescence imaging system has been developed using high precision linear translation stages and an electronic signal detection based on a low-cost PC sound card and a simple front-end electronics including a voltage controlled oscillator. The system has been used for the characterization of the photoresponse and of the light emission properties of crystalline silicon and GaAs solar cells. A direct comparison of the photocurrent and electroluminescence maps, as obtained by the developed system, with a conventional data acquisition using a IEEE 488 controlled picoamperemeter, showed basically no differences in the measurement results. In this way we could demonstrate, that PC sound card based acquisition systems can also be used for highly sensitive measurement applications. In the case of the electroluminescence mapping of solar cells, with interesting applications for example for defect imaging, we could easily detect optical powers in the nW range with the sound card based system. Good linearity and temporal stability of the frequency detection based data acquisition has been demonstrated. This opens the way to low-cost portable photovoltaic characterization equipment without the need to transport bulky and costly measurement instruments.