Incorporation of carbon quantum dots with PEDOT:PSS for high-performance inverted organic solar cells

Inverted organic solar cells (iOSCs) have attracted considerable attention because of their ease of fabrication and suitability for roll-to-roll processing. Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), with multiple favorable properties, is the most actively studied hole-transporting layer (HTL) material. However, the pristine state of PEDOT:PSS is limited by its inefficient, poor, and inhomogeneous conductivity. Herein, we demonstrate strategies to enhance the performance of iOSC devices by introducing carbon quantum dots (CQDs), which have controllable conductivity and band edges, into the PEDOT:PSS HTL. This is considered to be an efficient route for modifying the intrinsic properties and electrical conductivity of PEDOT:PSS. The CQDs were first synthesized through a microwave-assisted process by employing eco-friendly and low-cost material sources. By optimizing the ratio of CQDs incorporated into PEDOT:PSS (PH-G0.05), an iOSC with a remarkable enhancement of 3.90% in power conversion efficiency, was obtained. Using PH-G0.05 HTL helped to improve the contact quality and assisted the hole extraction/transport ability at the photoactive/top Ag anode interface with high electrical conductivity (2.80 S cm^–1), good surface morphology (RMS = 7.34 nm), and suitable work function (4.78 eV). Our efforts to develop a solution process for CQDs-incorporated PEDOT:PSS HTLs shows considerable promise for the potential replacement of vacuum-based methods in iOSC applications.