An Inorganic Hole Conductor for Organo-Lead Halide Perovskite Solar Cells. Improved Hole Conductivity with Copper Iodide

TLDR

Organo‑lead halide perovskite solar cells are promising next‑generation devices, yet they rely on expensive, low‑mobility organic hole conductors, and reducing recombination could make inorganic CuI a cost‑effective alternative. The study investigates copper iodide as a new inorganic hole conductor for perovskite thin‑film photovoltaics. Copper iodide achieved a 6.0 % power‑conversion efficiency with stable photocurrent, higher conductivity than spiro‑OMeTAD, and improved fill factor, though its open‑circuit voltage remains low due to increased recombination.

Abstract

Organo-lead halide perovskite solar cells have emerged as one of the most promising candidates for the next generation of solar cells. To date, these perovskite thin film solar cells have exclusively employed organic hole conducting polymers which are often expensive and have low hole mobility. In a quest to explore new inorganic hole conducting materials for these perovskite-based thin film photovoltaics, we have identified copper iodide as a possible alternative. Using copper iodide, we have succeeded in achieving a promising power conversion efficiency of 6.0% with excellent photocurrent stability. The open-circuit voltage, compared to the best spiro-OMeTAD devices, remains low and is attributed to higher recombination in CuI devices as determined by impedance spectroscopy. However, impedance spectroscopy revealed that CuI exhibits 2 orders of magnitude higher electrical conductivity than spiro-OMeTAD which allows for significantly higher fill factors. Reducing the recombination in these devices could render CuI as a cost-effective competitor to spiro-OMeTAD in perovskite solar cells.