Hole Transporting Layers in Solar Cells: Stabilizing NiO Perovskite Inks with Organic Capping Agents

Abstract

Increasing global demand for inexpensive energy has stimulated the development of sustainable alternative energy sources. One approach is the development of artificial water splitting electrocatalysts based on solid state materials, such as utilizing solar energy generated by perovskites for efficient O2 and H2 production from water. Perovskite solar cells is a growing field of efficient and affordable photovoltaic devises. Current systems use expensive organic poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) for hole transporting layers when constructed in the nip configuration. NiO is potentially an efficient alternative to PEDOT:PSS but cannot be used directly because its solubility in various solvent is similar to perovskites. Previous work has shown that capping agents can be added to NiO during in situ synthesis. Addition of organic capping agents to NiO should improve its solubility in alternative organic solvents enabling deposition on perovskite surfaces. NiO coated perovskite inks are cheaper than the PEDOT:PSS materials currently used and are ideal for mass production of perovskite solar cells. In this study, we will demonstrate a process for adding capping agents to pre-synthesized NiO particles. Earlier capping agents included long chain carboxylic acids and xanthates. Herein, we evaluated the effect of chain length reduction on the conductivity of NiO materials. In addition, we will demonstrate using PXRD, IR, and SEM that the addition of these capping agents maintains the NiO crystallinity and conductivity.