Vertical Concentration Distribution Engineering And Electrode Interfacial Layer Optimization In Polymer Solar Cells

Bulk-heterojunction polymer solar cells(BHJ-PSCs)have been considered as an attractive and promising approach to solve the energy and environment issues,due to their light-weight,low-cost,flexibility and high-throughput roll-to-roll manufacturing.The power conversion efficiency(PCE)of single juction BHJ-PSCs based on a conjugated polymer and a fullerene derivative has been exceeded by 13%.However,in order to realize the commercial application of polymer soalr cells,the efficiency and stability need to be further improved.The decive performance is greatly influenced by the morphology and the concentration distribution of the BHJ blends.An ideal BHJ blend should not only prompt exciton drift towards the interface of the donor and acceptor for efficient dissociation,but also offer continuous and unhindered pathways for easy carrier transport to the corresponding electrode.In this paper,we focused on the vertical concentration distribution of the photoactive layer in the fullerene and non fullerene polymer solar cells.The main contents are as follows:1.2-Chlorophenol was introduced to optimize the vertical concentration distribution of the donor and acceptor in the photoactive layer of fullerene-based polymer solar cells.2-chlorophenol was used to remove the PCBM on the top surface of the photoactive layer due to its selective solubility in PCBM and PTB7-Th.Compared with the control device without modulation of the concentration distribution,the short circuit current density(Jsc)increased from 13.19 to 18.50 mA cm-2 and the power conversion efficiency(PCE)increased from 6.18%to 10.15%for the inverted device with 2-chlorophenol flush treatment due to the greatly enhanced charge transportation and reduced exciton recombination.2.We investigated the donor and acceptor distribution within the non-fullerene photoactive layer based on PBDTTT-ET:IEICO by time-of-flight secondary-ion mass spectroscopy(TOF-SIMS)and scanning Kelvin probe microscopy(SKPM),indicating that more IEICO enriches on the surface of the photoactive layer.This distribution is more benificial to the charge transportation and collection in conventional device structure.To further understand the effect of the inhomogeneous component distribution on the photovoltaic performance,both conventional and inverted polymer solar cells were fabricated.As a result,the conventional device shows a power conversion efficiency(PCE)of 8.83%which is 41%higher than that of inverted one(6.26%).