Charge Transport between Coaxial Polymer Nanorods and Grafted All-Inorganic Perovskite Nanocrystals for Hybrid Organic Solar Cells with Enhanced Photoconversion Efficiency

Abstract

The versatile optoelectronic properties of perovskite nanocrystals (NCs) have provided a strong surge for their utilization in different classes of solar cells, with organic photovoltaic systems being no exception. In an unprecedented approach, a hybrid solar cell with CsPbBr1.5I1.5 NCs strategically grafted on poly(3-hexylthiophene-2,5-diyl) (P3HT) nanorods (NRs) is shown to have a photoconversion efficiency of 9.72 ± 0.4%, with only 1.5 wt % NCs. The improvement is twice more than the P3HT:PCBM reference devices (4.09 ± 0.2%). The choice of NC composition is validated by density functional theory calculations, which show decent charge carrier mobility in CsPbBr1.5I1.5, besides having better stability than CsPbI3, making CsPbBr1.5I1.5 NCs a suitable contender for hybrid device architecture. A trivial blending of the NCs in the P3HT:PCBM matrix results in their nonuniform distribution, escalating charge carrier trapping, albeit maintaining a device efficiency of 8.07 ± 0.3% with 1 wt % NCs. Uniform NC grafting is propitious over inhomogeneous blending because CsPbBr1.5I1.5 NCs not only act as additional light harvesters, but their chemical grafting onto the P3HT NRs improves the charge transport by creating better charge percolation pathways. The higher crystallinity of the P3HT NRs than P3HT also helps in reducing the trap states.