Energy levels in dilute-donor organic solar cell photocurrent generation: A thienothiophene donor molecule study

Murthy, Lakshmi N.S.; Kramer, Aaron; Zhang, Boya; Su, Jing-Mei; Chen, Yisheng; Wong, Ken‐Tsung; Vandenberghe, William G.; Hsu, Julia W. P.

doi:10.1016/j.orgel.2021.106137

Cited by 11 publications

(13 citation statements)

References 32 publications

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“…However, Figure d,e shows that V oc values for PC 71 BM and Y6 DD devices, respectively, with 5 wt % of different donors vary widely. While neat PC 71 BM device produces a V oc of 0.85 V, , adding 5 wt % of NBTT-Rho and PM6 increases V oc to above 0.9 V, while 5 wt % of PThDPP-FVF in PC 71 BM lowers the V oc to 0.65 V. Outside of this work, there was no published work on DD OPVs with solution-processable SM donors. V oc values of various SM donors in C 60 in vacuum-deposited DD devices are lower than those of neat C 60 devices. ,, PC 71 BM DD devices with several polymer donors were previously reported to exhibit similar V oc , leading to the proposal that V oc of DD devices was determined by Schottky barrier height. ,,, Our V oc results shown in Figure d clearly indicate the incompleteness of previous studies.…”

Section: Resultsmentioning

confidence: 94%

“…Instead of fitting the EQE PV spectra below the band gap with a Gaussian peak to determine E CT , , it was argued that a more accurate method to determine the E CT value is from the intersection point of Gaussian fits to the normalized EQE PV and EL spectra. , We apply this method to our PC 71 BM (Figure S3) and Y6 (Figure S4) DD devices and name the energy values at the intersection as E g int (Table ). ,, For Y6 DD devices, because the drop-off of the EQE PV signal is very steep (Figure c) with no discernible sub-band gap features, there are not as many decades in the EQE PV data for accurate fitting. Therefore, we determine the characteristic energy values using three methods: the intersection method described above, the energy at half of EQE PV maximum, and the energy at the maximum of the derivative of EQE PV .…”

Section: Resultsmentioning

confidence: 99%

“…However, Figure 2d,e shows that V oc values for PC 71 BM and Y6 DD devices, respectively, with 5 wt % of different donors vary widely. While neat PC 71 BM device produces a V oc of 0.85 V, 8,38 adding 5 wt % of NBTT-Rho and PM6 increases V oc to above 0.9 V, while 5 wt % of PThDPP- The standard deviations are calculated from at least 5 diodes from different runs. FVF in PC 71 BM lowers the V oc to 0.65 V. Outside of this work, there was no published work on DD OPVs with solutionprocessable SM donors.…”

Section: Methodsmentioning

confidence: 99%

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Re-Examining Open-Circuit Voltage in Dilute-Donor Organic Photovoltaics

et al. 2022

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Dilute-donor (DD) organic photovoltaic (OPV) devices comprise a low concentration of donor molecules in an acceptor matrix. The open-circuit voltage (V oc) of these devices is commonly higher than their bulk heterojunction (BHJ) counterparts and has been attributed to Schottky barrier heights between the anode and the acceptor matrix or reduced bimolecular recombination due to smaller donor/acceptor interfacial areas. Here, we examine the V oc of a variety of small-molecule and polymer donors, all at 5 wt %, in both fullerene and non-fullerene acceptors by performing photovoltaic (PV) and electroluminescence (EL) measurements on the same devices. We find a substantial V oc variation for different donors in the same acceptor matrix, indicating that DD V oc cannot be adequately explained by the Schottky barrier or interfacial area. V oc values of fullerene DD devices vary linearly with the band gap value as determined from the intercept of PV external quantum efficiency and EL spectra. In contrast, the non-fullerene acceptor (NFA) DD devices show V oc variation with donors despite having the same band gap. These results show that V oc of DD OPVs is predominantly determined by non-radiative voltage loss, similar to BHJ OPVs. NFA-based DD devices show promises for low voltage loss and high charge generation.

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Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Re-Examining Open-Circuit Voltage in Dilute-Donor Organic Photovoltaics

et al. 2022

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“…Highly diluted polymer donor chains may not form a percolating network for charge extraction, in contrast to the common morphological picture for BHJ solar cells. Theoretical and experimental work aims to explain successful photocurrent generation in such highly diluted donor (fullerene) OPVs with isolated donor molecules by a hole back-transfer mechanism that is dependent on the HOMO-HOMO offset between donor and acceptor [113,116,117].…”

Section: Current Performance and Strategies To Increase Luementioning

confidence: 99%

A Review on the Materials Science and Device Physics of Semitransparent Organic Photovoltaics

Schopp

Брус

2022

Energies

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In this review, the current state of materials science and the device physics of semitransparent organic solar cells is summarized. Relevant synthetic strategies to narrow the band gap of organic semiconducting molecules are outlined, and recent developments in the polymer donor and near-infrared absorbing acceptor materials are discussed. Next, an overview of transparent electrodes is given, including oxides, multi-stacks, thin metal, and solution processed electrodes, as well as considerations that are unique to ST-OPVs. The remainder of this review focuses on the device engineering of ST-OPVs. The figures of merit and the theoretical limitations of ST-OPVs are covered, as well as strategies to improve the light utilization efficiency. Lastly, the importance of creating an in-depth understanding of the device physics of ST-OPVs is emphasized and the existing works that answer fundamental questions about the inherent changes in the optoelectronic processes in transparent devices are presented in a condensed way. This last part outlines the changes that are unique for devices with increased transparency and the resulting implications, serving as a point of reference for the systematic development of next-generation ST-OPVs.

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“…Dilute donor organic solar cells (DDOSCs), which have active layers containing a low concentration of donor molecules in an acceptor matrix, are intriguing because they can achieve a high open-circuit voltage ( V oc ) and a high short-circuit current density ( J sc ) simultaneously. − Most DDOSC research utilizes fullerene-based acceptors. ,,− However, fullerene-based acceptors have low optical absorption in the visible region and low hole mobility, both detrimental to photocurrent generation. In contrast, several non-fullerene acceptors (NFAs) exhibit strong absorption across a larger portion of the solar spectrum and high mobilities with ambipolar characteristics .…”

Section: Introductionmentioning

confidence: 99%

Contributions of Charge Generation Versus Transport to Photocurrent in Dilute-Donor Organic Solar Cells with Non-fullerene Acceptors

Zhang

Bonner

et al. 2022

J. Phys. Chem. C

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The photocurrent generation in dilute donor organic solar cells (DDOSCs) based on fullerene and non-fullerene acceptors is compared. The donor concentration is kept under 5 wt % to avoid the formation of a percolation pathway for hole transport, as verified by studying the hole mobilities in an insulating polymer matrix. The short-circuit current densities (J sc ) in DDOSCs for three common acceptors are quantified in terms of charge generation, transport, and collection, which are probed using ideal J sc calculated from the transfer matrix method, hole mobility measured from space charge limited current method, and charge collection efficiency, respectively. Using non-fullerene acceptors improves both charge generation and transport, with charge transport being more important in determining J sc in DDOSCs.

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Energy levels in dilute-donor organic solar cell photocurrent generation: A thienothiophene donor molecule study

Cited by 11 publications

References 32 publications

Re-Examining Open-Circuit Voltage in Dilute-Donor Organic Photovoltaics

Re-Examining Open-Circuit Voltage in Dilute-Donor Organic Photovoltaics

A Review on the Materials Science and Device Physics of Semitransparent Organic Photovoltaics

Contributions of Charge Generation Versus Transport to Photocurrent in Dilute-Donor Organic Solar Cells with Non-fullerene Acceptors

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