Decoupling Thin Film CdTe Growth from Packaging: Toward Record Specific Power in Low Cost Polycrystalline PV

There are critical material and scientific barriers to producing high efficiency, flexible, lightweight solar cells that maximize specific power in a cost-effective manner. III-V solar cells have produced the highest specific power of any photovoltaic technology due to their extremely high efficiency, however, they are also among the most expensive to produce. This work explores a novel lift-off approach with thin-film solar cells, particularly CdTe, to achieve high specific power at low costs. Thin-film devices can be delaminated from their heavy, glass growth substrates post-growth by exploiting a mismatch in coefficient of thermal expansion between the two. This allows thin-film PV to be decoupled from high temperature growth requirements and repackaged using lightweight materials. In this work we evaluate different materials and approaches for achieving large area delamination of CdTe films from their glass superstrates. It is found that epoxy bonded to a rigid handle provides robust and reproducible delamination at the TCO/CdS interface upon submersion in liquid nitrogen. Following delamination, a transparent front contact is re-deposited and selectively etched to expose the back contact to produce a functioning device. Effects of delamination and contributions to device functionality from CdCl 2 and CdS layers are discussed. Reproducible delamination of high efficiency, thin-film solar cells over large areas will enable work to further improve device efficiency through passivation and reconstruction of the previously buried interface between the transparent contact and CdS.