Optically probed the charge carrier lifetime below the surface of solar materials using two-photon (2P) time-resolved PL mapping, and demonstrated that the traditional one-photon (1P) technique can underestimate the bulk lifetime in CdTe by 10x.
Significance and Impact
Improving carrier lifetime is a critical component in boosting solar cell efficiencies, but accurately measuring the bulk carrier lifetime is one of the greatest challenges in evaluating solar materials. 2P tomography can non-destructively map bulk lifetime, surface recombination and other properties within photovoltaic materials to locate areas of reduced device performance.
- Current optical techniques such as 1P photoluminescence probe the surface of solar cells where surface defects can hide true bulk lifetime.
- 2P optical excitation allows excitation below the surface of the sample and thus enables non-destructive measurement of bulk properties.
- Multidimensional maps of lifetime and emission spectra were created. 3D lifetime tomography is now possible and currently under development.