Highly photostable and efficient semitransparent quantum dot solar cells by using solution-phase ligand exchange

Abstract

For semitransparent solar cells (SSCs) the photovoltaic efficiency and the transparency are the two primary objectives for utilization in for example building integrated photovoltaics. Solution-processed PbS colloidal quantum dot (CQD) has strong light absorption in the ultraviolent region and possess the advantages of tunable bandgap in the visible and infrared region. Herein we report a PbS CQD-SSC with tunable infrared light absorption and high photostability by combining experimental studies and numerical theoretical simulations. Through fine-controlling the electro-optics in the CQD-SSC and by using a solution-phase ligand exchange for the CQD solid film deposition, the power loss in the device is significantly decreased, yielding a CQD-SSC with a power conversion efficiency of 8.4% and an average visible transmittance of 21.4%, respectively. After 540 h continuous 100 mW cm−2 illumination the solar cell still shows ~ 85% of its initial power conversion efficiency, and then recovers to the initial performance after storage in dark. This work provides a strong progress and an approach toward the development of low-cost, highly efficient and stable semitransparent CQD solar cells. Meanwhile this study also provides insight and quantitative guidelines for further improving the SSC photovoltaic efficiency and transparency in general.