Colloidal Quantum Dots for Highly Efficient Photovoltaics

Abstract

Owing to strong quantum confinement, solution-processed colloidal quantum dots (CQDs) provide a unique route for fabrication of highly efficient photovoltaics to overcome the Shockley-Queisser limit through multiple exciton generation (MEG). Also, the CQDs PVs are cost-effective due to fabrication at low temperatures. Despite the high quantum limit of 42–44%, the highest experimental power conversion efficiency reported so far in PbS CQD PVs still remains at ~11.2%. Recent studies have shown that the performance of CQD solar cells is mainly limited by defects through different recombination channels. In this work, we identify the reasons for a large open circuit voltage (VOC) deficit, associated with short diffusion length and lifetime of minority carriers by different types of defect recombination pathways in the devices. We also summarize recent progress in improvement of device efficiency through treatment of defect. Surface modification is primarily intended to passivate surface defects in CQDs. Whereas, interface defects can be treated by engineering of transport layers or device architecture through, e.g., ionic doping or additional layers, entailing fast dissociation and smooth transport of charge carriers at junctions.