Recent Developments in Quantum Dots/CNT Co-Sensitized Organic Solar Cells

Abstract

Polymer solar cells (PSCs) are emerging alternative candidates to the standard silicone technology for green and renewable energy generation owing to their flexibility and solution processability. Bulk heterojunction (BHJ) organic solar cells (OSCs) based on conjugated semiconducting polymers as donor (D) and fullerene derivatives as acceptor (A) offer large D/A interfacial area, which overcomes the short exciton diffusion length. Although, recent advances in narrow band gap semiconducting polymers have led to the improvement in power conversion efficiency of organic photovoltaics (OPVs) beyond 10%, inefficient charge separation and low carrier mobility as well as negligible photon harvesting in near-infrared (NIR) and/or infrared (IR) region of the solar spectrum have still remained as bottle neck for ultimate performance of OPVs. Most PSCs only absorb the UV-visible part of the solar spectrum, leading to the low light harvesting efficiency. Hence, solution processed photoactive materials comprising nanostructured semiconducting inorganic quantum dots (QDs) as sensitizer have attracted great attention to improve energy conversion efficiency of the OPVs. This is attributed to the outstanding optoelectronic properties of QDs such as band gap tunability, potential NIR photons harvesting and multi exciton generation (MEG). However, the main shortcoming of inorganic QDs based OSCs is randomly hopping charge transport among discrete QD particles, which can be tackled through hybridization with one dimensional (1D) electrically conductive nanostructured materials such as carbon nanotube (CNT). By this way, CNT particles would behave as support for anchoring the light harvesting semiconductor QDs, leading to the enhancement of the exciton dissociation and charge transport towards the corresponding electrodes. Recently, manufacturing PSCs co-sensitized by QD loaded CNT has been shown as a promising direction to maximize performance of the device. This article reviews the recent developments in enhancement of OPVs" performance by utilization of high efficient light harvesting QDs and/or their hybrid with 1D CNTs.