A Dual Functional Polymer Interlayer Enables Near‐Infrared Absorbing Organic Photoanodes for Solar Water Oxidation (Adv. Energy Mater. 18/2022)

Lee, Tack Ho; Rao, Reshma R.; Pacalaj, Richard A.; Wilson, Anna A.; Durrant, James R.

doi:10.1002/aenm.202270073

Cited by 7 publications

(19 citation statements)

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“…[ 20 ] High‐quality PM6 films can be transferred on top of IT4F films without damage by this polymer film transfer technique, as reported in previous literature. [ 12a,21 ] This film transfer technique has also been highlighted as achieving the uniform and conformal formation of organic films on the various substrates. [ 22 ] The IT4F/PM6 planar heterointerface was clearly shown in high‐resolution transmission electron microscopy image (Figure S5, Supporting Information).The presence of a sharp IT4F/PM6 interface enables a clear investigation of the impact of IT4F layer thickness on PHJ photophysics and device performance.…”

Section: Resultsmentioning

confidence: 99%

Organic Planar Heterojunction Solar Cells and Photodetectors Tailored to the Exciton Diffusion Length Scale of a Non‐Fullerene Acceptor

Lee

Dong

Pacalaj

et al. 2022

Adv Funct Materials

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While non‐fullerene acceptors (NFAs) have recently been demonstrated to exhibit long‐range exciton diffusion, most organic photovoltaic and photodetector studies still focus on blended polymer: NFA systems. Herein, a 40 nm exciton diffusion length for IT4F excitons is determined, and it is demonstrated that sharp interface, planar heterojunction (PHJ) IT4F/PM6 devices with the IT4F layer thickness matched to this diffusion length yield optimized photovoltaic and photodetector performance. The PHJ devices yield an enhanced device open‐circuit voltage relative to bulk heterojunction (BHJ) devices, associated with suppressed bimolecular recombination losses. The PHJ architecture also results in a ≈100‐fold increase in electroluminescence (EL) quantum efficiency relative to the BHJ device, correlated with a shift from charge transfer state EL for the BHJ to IT4F exciton dominated EL for the PHJ, attributed to significant hole injection from PM6 into IT4F. Of particular note, the PHJ architecture is shown to suppress dark leakage current, resulting in 83 times higher photodetector detectivity at −2 V bias than the equivalent BHJ device.

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Section: Resultsmentioning

confidence: 99%

Organic Planar Heterojunction Solar Cells and Photodetectors Tailored to the Exciton Diffusion Length Scale of a Non‐Fullerene Acceptor

Lee

Dong

Pacalaj

et al. 2022

Adv Funct Materials

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“…[ 4 ] Highly efficient OPV devices have been developed based on bulk heterojunctions (BHJs) of a polymer donor and a small molecular acceptor. These are a promising alternative to the inorganic metal oxide semiconductors typically used in PEC devices, due in particular to their wide absorption range up to the near infrared (NIR), [ 5 ] whilst most metal oxides PEC can utilize only near‐ultraviolet or blue light. [ 6 ] Recent efficiency advances in OPVs have been driven by the development of non‐fullerene small molecular acceptors, with high performances attributed in particular to their longer exciton lifetimes; [ 7 ] however, the nanosecond–microsecond timescale of charges photogenerated in the BHJ is still much shorter than the millisecond–second timescales of photocatalysis.…”

Section: Introductionmentioning

confidence: 99%

“…We have previously used a polymer overlayer in an organic photoanode to improve operational stability and suppress accumulated hole recombination. [ 5 ] In that study, we optimized organic BHJ‐based photoanodes by sandwiching Y6:PM6 BHJ with ZnO nanoparticles and a PM6 overlayer, improving operational stability underwater. [ 5 ] After depositing Au/NiFe catalyst on the organic photoanode, a photocurrent density of 4.0 mA cm −2 at 1.23 V versus the reversible hydrogen electrode (1.23 V RHE ) was achieved with 100% Faradaic efficiency.…”

Section: Introductionmentioning

confidence: 99%

Long‐Lived Charges in Y6:PM6 Bulk‐Heterojunction Photoanodes with a Polymer Overlayer Improve Photoelectrocatalytic Performance

Lee

Hillman

González‐Carrero

et al. 2023

Advanced Energy Materials

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Photogenerating charges with long lifetimes to drive catalysis is challenging in organic semiconductors. Here, the role of a PM6 polymer overlayer on the photoexcited carrier dynamics is investigated in a Y6:PM6 bulk‐heterojunction (BHJ) photoanode undergoing ascorbic acid oxidation. With the additional polymer layer, the hole lifetime is increased in the solid state BHJ film. When the photoanode is electrically coupled to a hydrogen‐evolving platinum cathode, remarkably long‐lived hole polaron states are observed on the timescale of seconds under operational conditions. It is demonstrated that these long‐lived holes enable the organic photoanode with the polymer overlayer to show enhanced ascorbic acid oxidation performance, reaching ≈7 mA cm−2 at 1.23 VRHE without a co‐catalyst. An external quantum efficiency of 18% is observed using 850 nm excitation. It is proposed that the use of an organic overlayer can be an effective design strategy for generating longer charge carrier lifetimes in organic photoanodes for efficient oxidation catalysis.

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“…[ 21 ] Indeed, this BHJ concept has recently been leveraged with photoelectrodes and photocatalysts to achieve breakthrough performance in either solar‐driven water reduction [ 22–24 ] or water oxidation. [ 25,26 ] Moreover, the stability of the OS‐based PEC devices has been addressed. [ 24 ] Despite this progress, overall water splitting has not been demonstrated with OS‐based PEC or PC systems that leverage the BHJ concept.…”

Section: Introductionmentioning

confidence: 99%

An Organic Semiconductor Photoelectrochemical Tandem Cell for Solar Water Splitting

Zhang

Cho

Yum

et al. 2022

Advanced Energy Materials

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PC) systems can potentially realize green H 2 in an economically competitive and scalable manner. Indeed, since the lightharvesting semiconductor material is placed in direct contact with water in the PEC and PC approaches the system complexity is minimized. [2][3][4] Because an ideal single semiconductor whose energy band positions straddle the water reduction and oxidation potentials while maximizing solar energy collection remains elusive, the dual-absorber approaches (i.e., the PEC tandem cell [5][6][7] and PC Z-scheme [8][9][10] ) are currently under intense development. In a PEC tandem cell, a photocathode and a photoanode are configured in series, and both absorb part of the incident sunlight to drive the water reduction and oxidation reactions, respectively, while exchanging charges via a direct electrical connection. Analogously in a PC Z-Scheme, hydrogen evolution particles and oxygen evolution particles drive the water splitting reactions while electronically communicating via a redox shuttle.Despite decades of research in these systems, the demonstration of high-performance solar water splitting with inexpensive and scalable systems remains challenging in part due to the absence of ideal semiconductor materials. [11] Organic semiconductors (OSs) are rapidly emerging as promising candidates to tackle this challenge. [12][13][14][15][16][17] OSs are characterized by polymers or small molecules with extended pi-conjugation of carbon bonds and possess many promising properties including energy levels that can be easily tailored through molecular engineering, and excellent light harvesting properties derived from relatively high molar extinction coefficients. [18] In addition, OSs can be solution-processed at ambient temperatures, which facilitates the economical fabrication of large-area thin film devices [19] or the scalable production of nanoparticle photocatalysts. [20] Furthermore, as well established in the field of organic photovoltaics, when an electron donating OS is placed in contact with an electron accepting OS to form a bulk heterojunction (BHJ) structure (where they are well-intermixed at a ≈10 nm length scale), free charge carriers are efficiently photogenerated and separated-a process that can be easily adjusted by varying the combination of donor and acceptor. [21] Indeed, this BHJ concept has recently been leveraged with photoelectrodes and photocatalysts to achieve breakthrough performance in either solar-driven water reduction [22][23][24] or water oxidation. [25,26] Moreover, the stability of the OS-based PEC devices has been addressed. [24] Despite this progress, overall water splitting has not been demonstrated with OS-based PEC or PC systems that leverage the BHJ concept.Photoelectrochemical cells employing organic semiconductors (OS) are promising for solar-to-fuel conversion via water splitting. However, despite encouraging advances with the half reactions, complete overall water splitting remains a challenge. Herein, a robust organic photocathode operating in near-neutral pH elec...

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A Dual Functional Polymer Interlayer Enables Near‐Infrared Absorbing Organic Photoanodes for Solar Water Oxidation (Adv. Energy Mater. 18/2022)

Cited by 7 publications

References 0 publications

Organic Planar Heterojunction Solar Cells and Photodetectors Tailored to the Exciton Diffusion Length Scale of a Non‐Fullerene Acceptor

Organic Planar Heterojunction Solar Cells and Photodetectors Tailored to the Exciton Diffusion Length Scale of a Non‐Fullerene Acceptor

Long‐Lived Charges in Y6:PM6 Bulk‐Heterojunction Photoanodes with a Polymer Overlayer Improve Photoelectrocatalytic Performance

An Organic Semiconductor Photoelectrochemical Tandem Cell for Solar Water Splitting

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