3D Lifetime Tomography Reveals How CdCl2 Improves Recombination Throughout CdTe Solar Cells

Spatially resolved 3D carrier-lifetime maps were measured using 2P tomography to uncover carrier dynamics at buried structures in CdTe thin-films photovoltaics. When thin-film CdTe solar cells are initially deposited, we observe increased nonradiative carrier recombination at GBs throughout the 3D volume of the film, which is most pronounced in the critical junction region where small nucleation grains form at the buried CdTe/CdS interface. The data on CdTe films treated by exposure to CdCl2vapor reveal that a critical function of the treatment is to reduce surface, interface and GB recombination throughout the entirety of these polycrystalline films. The CdCl2treatment may also compensate CdTe films, making it difficult to exceed a hole density of 1015m-3and achieve higher current density and efficiency.