Role of the Seed and Electron Transport Layers in GeSe Thin Film Photovoltaics

This work investigates the use of closed‐spaced sublimation for deposition of GeSe thin films for photovoltaics. Film quality was optimised via an in situ substrate annealing process for the production of functioning devices. The influence of both and CdS electron transport layers (ETLs) was studied both with and without the addition of an seed layer. Besides enabling high power conversion efficiencies (PCEs), the role of the seed layer was studied and a beneficial modification to subsequent GeSe growth was found. In addition to this, a large contribution to light absorption and photocurrent generation was found for layers thicker than 50 nm. Devices with a reduced thickness seed layer down to 2 nm were fabricated in which ETL devices out‐performed those with CdS for PCE up to 1.75%.