A nanoparticle ink printing process for all printed thin film copper-indium-selenide (CIS) solar cells

摘要

Copper indium selenide (CIS) or its derivatives (such as gallium doped CIS and sulfur substituted CIS) are considered the best optical absorber material used in polycrystalline thin film photovoltaic solar cells due to their favorable electrical and optical properties, and long term stability. To develop a low cost yet high throughput thin film deposition process with both composition and film uniformity control, precursor ink has been formulated using nanoparticle metal oxide of copper and indium in an organic solvent system dissolved with selenium or sulfur. Smooth thin film of precursor oxide mixture has been demonstrated by wet printing process. Upon heat treatment of the precursor thin film under atmosphere of selenium and/or sulfur, copper-indium selenide and/or sulfide (CIS) was formed. Several approaches of nanoparticle ink coating processes have been investigated through spin-coating, screen-printing and contact printing. For using glass substrate, contact printing demonstrated superior uniformity and composition control. By using a post-thermal treatment process on the nanoparticle-coated film, good morphology thin film with composition control was achieved. Both the chemical composition and physical morphology has been investigated using ICP-OES and XRD measurements. Based on molybdenum glass substrate, all-printed solar cells have been demonstrated.