Electrodeposition of poly and nanocrystalline Cu-In-Se absorbers for optoelectronic devices

Abstract

Coupling semiconductors with electrochemical processes can lead to unusual materials, and attractive, practical device configurations. This work examines the reaction mechanism for single-step electrodeposition approach that creates device quality copper-indiumselenide (CISe) films with either polycrystalline or nanocrystalline morphologies on Cu and steel foils, respectively. The polycrystalline CISe film grows from In ⁺/Se ⁺ solution on Cu foil as Cu→ Cu_xSe→ CuInSe₂; it may be used in standard planar pn devices. The nanocrystalline CISe film grown from Cu⁺/In³⁺/Se⁴⁺ solution follows the CuSe(In) → CuInSe₂→ CuIn₃Se₅ sequence. The latter approach leads to naturally ordered, spacefilling nanocrystals, comprising interconnected 3-dimensional network of sharp, abrupt, p-CISe/n-CISe bulk homojunctions with extraordinary electro-optical attributes. Sandwiching these films between band-aligned contact electrodes can lead to high performance third generation devices for solar cells, light emitting diodes or photoelectrodes for fuel cells. Both approaches produce self-stabilized CISe absorbers that avoid recrystallization steps and can be roll-to-roll processed in simple flexible thin-film form factor for easy scale-up.