Solution‐Processed Polymer Solar Cells with over 17% Efficiency Enabled by an Iridium Complexation Approach

Abstract

as low-cost solution-processing, lightweight, and easy fabrication of flexible and semitransparent devices. [1][2][3][4][5][6] The device efficiencies have been continuously increasing in the last two decades, [7][8][9] enabled by crosscollaboration among material scientists, physicists, and device specialists; featured material synthesis (especially for nonfullerene acceptors (NFAs), [7,[10][11][12][13][14][15][16] ) optimized BHJ blend processing; [17,18] and detailed understanding on the physical mechanisms. [19][20][21][22][23][24] Very recently, benefiting from the new NFA material synthesis, the power conversion efficiency (PCEs) over 16% in binary solar cells have been realized, [25][26][27][28] which make the solution-processed BHJ PSCs viable for practical applications in the near future.In the active layers, the BHJ morphology architecture helps the photogenerated excitons to dissociate into charge carriers at the D/A interfaces. [29,30] The free carriers diffuse/drift by the built-in electric field and can be further collected at the relevant electrodes via a continuous network of D/A materials. In the process of converting photons to a flow of electricity, efficient charge generation, fast charge carrier extraction, and less carrier recombination loss are prerequisites for realizing high performance devices. [31] However, the requirements of these three competitors (including charge generation, carrier recombination, and extraction) with regard to the interface area of the D/A (morphology) and the active layer thickness are conflicting on the one hand. [32] On the other hand, the optoelectronic properties of the D/A materials, the processing conditions, and the device structures can also greatly determine the properties of the three competitors, which in turn affect device performance. [24,31,33] Thus, finding an effective strategy or approach for simultaneously facilitate charge generation, accelerate carrier extraction, and hinder carrier recombination is very important to further improve device performance.In the organic semiconductors, the excitons of many semiconducting polymers have lifetimes in the range of 10-100 ps, [34] and the relevant diffusion lengths of 5-10 nm, [35] which generally constrain the D/A domain sizes and layer thickness in the active layers. As expected, the above-mentioned three competitors are seriously sensitive to the interface area of the nanoscale morphology, the D/A domain size, and the active layer thickness in BHJs. Many studies demonstrated that photovoltaic materials incorporated with a small amount of complexes or components can improve the relevant blend morphology and photovoltaic performance, especiallyThe commercially available PM6 as donor materials are used widely in highly efficient nonfullerene polymer solar cells (PSCs). In this work, different concentrations of iridium (Ir) complexes (0, 0.5, 1, 2.5, and 5 mol%) are incorporated carefully into the polymer conjugated backbone of PM6 (PM6-Ir0), and a set of π-conjugated polymer donors (named PM6-Ir0.5, PM...

Understanding the Effect of End Group Halogenation in Tuning Miscibility and Morphology of High‐Performance Small Molecular Acceptors

“…[ 1–6 ] Nonfullerene small molecular acceptors (SMAs) [ 7–29 ] are the main driving force for the recent development of the field, with power conversion efficiencies (PCEs) over 17% reported by different teams. [ 30–43 ] SMAs have many attractive properties including their strong and tunable absorption, the easily adjustable energy levels and the enhanced chemical and device stability. Most of these excellent features are enabled by the flexible and feasible synthesis of the SMAs that leads to numerous judiciously designed molecular structures.…”

Machine learning for accelerating the discovery of high-performance donor/acceptor pairs in non-fullerene organic solar cells

“…However, these examples of the application of ML algorithms were mostly used in the fullerene-based OSCs, whereas the reports about the application of ML algorithms in the non-fullerene-based OSCs are limited [41][42][43] . As non-fullerene acceptors (NFAs) draw researchers' attention and have become research hotspots [44][45][46] , and most state of art OSCs with efficiency up to 13-17% were achieved by NFA OSCs in these few years 4,47,48 , we shoud pay more attention to the applications of ML approaches that would tackle broader and more complex non-fullerene OSCs. Notably, the main challenges associated with screening the ideal photovoltaic materials from diverse non-fullerene systems are not only the selection of optimal algorithms but also the construction of training data sets.…”

Isomerization Strategy of Nonfullerene Small‐Molecule Acceptors for Organic Solar Cells

“…[ 34–40 ] Among a myriad of NFAs, rylene imides/amides and acceptor–donor–acceptor (A–D–A) type acceptors are the most important classes and exhibit promising performance in current researches. [ 41–51 ] To date, OSCs have yielded power conversion efficiencies (PCE) over 11% [ 52 ] for PDI‐based devices and over 17% [ 53–63 ] for A–D–A‐type SMA‐based devices, even OSCs with efficiencies over 18% have been realized. [ 58 ]…”