Smart Materials

Photocarriers in semiconductors excited by modulated laser sources give rise to diffusion waves that can be used to study and characterize the electronic properties of materials and devices. In this talk the concept of carrier diffusion waves will be introduced. Then, lock-in carrierography (LIC), a near-infrared (NIR) - camerabased quantitative diffusionwave methodology developed in the CADIPT for non-destructive imaging of electronic materials and devices, will be presented. With the recent advent of the heterodyne mode (HeLIC), high-frequency imaging up to and beyond 1a00kHz has been achieved, which allows hundred-Hz frame-rate NIR cameras to map out carrier-diffusion-wave microsecond recombination dynamics in active optoelectronic devices like solar cells. Beyond today’s state-of-the-art single effective- lifetime imaging, the high-frequency information from HeLIC can help resolve multiple carrier recombination rates/ lifetimes.

 

 

Fig.1. Introducing the rate-window, a resonant time-gated modality applied to decaying photocarrier diffusion-wave temporal profiles in Si solar cells

 

 

 

Fig.2. the resulting time-resolved tomography (coined definition:“lifetime chronotomography”) will be shown to give rise to three- dimensional space-time reconstructions of superposed multiple lifetime modes in solar cells, thus providing novel penetrating physical insights into the solar energy conversion/loss mechanisms.