Role of Polymer in Hybrid Polymer/PbS Quantum Dot Solar Cells

Hybrid nanocomposites (HCs) obtained by blend solutions of conjugated polymers and colloidal semiconductor nanocrystals are among the most promising materials to be exploited in solution-processed photovoltaic applications. The comprehension of the operating principles of solar cells based on HCs thus represents a crucial step toward the rational engineering of high performing photovoltaic devices. Here we investigate the effect of conjugated polymers on hybrid solar cell performances by taking advantage from an optimized morphology of the HCs comprising lead sulfide quantum dots (PbS QDs). Uncommonly, we find that larger photocurrent densities are achieved by HCs incorporating wide-bandgap polymers. A combination of spectroscopic and electro-optical measurements suggests that wide-bandgap polymers promote efficient charge/exciton transfer processes and hinder the population of midgap states on PbS QDs. Our findings underline the key role of the polymer in HC-based solar cells in the activation/deactivation of charge transfer/loss pathways.