Enhanced charge transport in low temperature carbon-based n-i-p perovskite solar cells with NiOx-CNT hole transport material

Abstract

We report oleylamine functionalized NiOx (f-NiOx) and CNT composite (f-NiOx + CNT) as hole transport material in n-i-p low-temperature processed carbon counter electrode based perovskite solar cells. Oleylamine functionalization improves the dispersibility of NiOx, but it reduces the conductivity. We demonstrate the addition of a small amount of CNT significantly enhances the conductivity and charge transport properties. The morphological and optoelectrical properties of prepared nanoparticles were evaluated using transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and UV–Vis spectroscopy. The results suggest suitable energy band alignment of f-NiOx+CNT hole transport material with FA0.83Cs0.17PbI2.5Br0.5 perovskite absorber layer. Better hole extraction and transport were provided by f-NiOx + CNT hole transport material, with improved conductivity of 2.73 × 10−2 S cm−1. The fabricated device exhibits 11.36% efficiency with exceptional stability for more than 720 h (retaining ~ 60% of initial efficiency) in ambient without encapsulation. Additionally, we have also demonstrated the perovskite mini-module by connecting two small area cells in series, making the active area of 4 cm2 with 6.11% efficiency.