17% Efficient Organic Solar Cells Based on Liquid Exfoliated WS₂ as a Replacement for PEDOT:PSS

Abstract

The application of liquid‐exfoliated 2D transition metal disulfides (TMDs) as the hole transport layers (HTLs) in nonfullerene‐based organic solar cells is reported. It is shown that solution processing of few‐layer WS2 or MoS2 suspensions directly onto transparent indium tin oxide (ITO) electrodes changes their work function without the need for any further treatment. HTLs comprising WS2 are found to exhibit higher uniformity on ITO than those of MoS2 and consistently yield solar cells with superior power conversion efficiency (PCE), improved fill factor (FF), enhanced short‐circuit current (JSC), and lower series resistance than devices based on poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) and MoS2. Cells based on the ternary bulk‐heterojunction PBDB‐T‐2F:Y6:PC71BM with WS2 as the HTL exhibit the highest PCE of 17%, with an FF of 78%, open‐circuit voltage of 0.84 V, and a JSC of 26 mA cm−2. Analysis of the cells' optical and carrier recombination characteristics indicates that the enhanced performance is most likely attributed to a combination of favorable photonic structure and reduced bimolecular recombination losses in WS2‐based cells. The achieved PCE is the highest reported to date for organic solar cells comprised of 2D charge transport interlayers and highlights the potential of TMDs as inexpensive HTLs for high‐efficiency organic photovoltaics.

17.1% Efficient Single‐Junction Organic Solar Cells Enabled by n‐Type Doping of the Bulk‐Heterojunction

“…In recent years, most efforts have been dedicated to the design of new materials with improved charge carrier mobility, optimized light absorption characteristics, and carefully tuned bulk heterojunction (BHJ) microstructures. As a result, power conversion efficiency (PCE) values of 17% for single‐junction and well over 17% for tandem OPVs, respectively, have been achieved 2–4. Despite the impressive progress, however, the aforementioned levels of performance are still lower than the practical PCE limits that are predicted to surpass 20% and 25% for single‐junction and tandem OPV cells, respectively 5.…”

Realizing Ultrahigh Mechanical Flexibility and >15% Efficiency of Flexible Organic Solar Cells via a “Welding” Flexible Transparent Electrode

“…[ 1–4 ] Flexible organic solar cells (OSCs) that employ a plastic substrate and organic active layer provide the feasibility for producing high specific power (the ratio of power to device weight) and excellent intrinsic mechanical flexibility. [ 4–13 ] So far, the highest reported power conversion efficiency (PCE) for flexible single‐junction OSCs is 14.06%, [ 14 ] which is lower than that of the corresponding rigid device with the highest PCE of over 17%, [ 15 ] and even the large‐area rigid OSCs (> 1 cm 2 ) demonstrate a higher PCE of 15.3%. [ 10 ] The reasons for the inferior performance of the flexible OSCs originate from the different optoelectronic and physical properties between glass and plastic substrate materials as well as the deposited transparent electrodes.…”

Fullerene‐Based Interlayers for Breaking Energy Barriers in Organic Solar Cells

“…This emerging photovoltaic technology has been the focus of academic and industrial community for decades, due to the great advantages in fabricating lightweight, flexible devices through inexpensive large area solution processing . The last two decades have seen dramatic increases of power conversion efficiencies (PCEs) from 1 % to >17 % in single‐junction devices due to tremendous efforts in device engineering and the synthetic tailoring on the chemical structure of organic semiconductors . One critical issue in OSCs is the charge extraction and transport between metal electrodes and organic semiconductors .…”