Conditions for efficient charge generation preceded by energy transfer process in non-fullerene organic solar cells

Benatto, Leandro; Moraes, C. A. M.; Candiotto, Graziâni; Sousa, Karlisson Rodrigo de Almeida; Souza, J. P. A.; Roman, Lucimara S.; Koehler, Marlus

doi:10.1039/d1ta06698f

Cited by 21 publications

(20 citation statements)

References 104 publications

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“…This procedure was performed using the polarizable continuum model (PCM) to simulate the molecule in a dielectric medium. It was found that these methods were able to calculate molecular energies that are in better agreement with experimental values. ,, The dielectric constants of each molecule applied in the PCM calculation were obtained from ref . We also calculated the atomic charges via the electrostatic potential (ESP) method − to obtain the magnitude of the internal charge transfer (ICT) between the acceptor chemical units and the donor chemical unit of the molecules.…”

Section: Materials and Methodsmentioning

confidence: 96%

“…A lower driving force is important to increase the device’s open-circuit voltage, − favoring the energy transfer process from donor to NFAs . The energy transfer followed by hole transfer is an important mechanism for free charge generation that increases the relevance of NFAs in the photovoltaic process . There are also reports of OSCs based on NFAs that showed very interesting features such as ultrafast charge transfer, , low charge trapping, and high morphological stability .…”

Section: Introductionmentioning

confidence: 99%

“…26 The energy transfer followed by hole transfer is an important mechanism for free charge generation that increases the relevance of NFAs in the photovoltaic process. 27 There are also reports of OSCs based on NFAs that showed very interesting features such as ultrafast charge transfer, 28,29 low charge trapping, 30 and high morphological stability. 31 Despite these characteristics of NFAs, further improvements have been sought.…”

Section: Introductionmentioning

confidence: 99%

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Binding Energy of Triplet Excitons in Nonfullerene Acceptors: The Effects of Fluorination and Chlorination

et al. 2022

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One strategy to improve the photovoltaic properties of nonfullerene acceptors (NFAs), employed in state-of-art organic solar cells, is the rational fluorination or chlorination of these molecules. Although this modification improves important acceptor properties, little is known about the effects on the triplet states. Here, we combine the polarizable continuum model with an optimally tuned range-separated hybrid functional to investigate this issue. We find that fluorination or chlorination of NFAs decreases the degree of the highest occupied molecular orbital− lowest unoccupied molecular orbital (HOMO−LUMO) overlap along these molecules. Consequently, the energy gap between T 1 and S 1 states, ΔE ST = E S1 − E T1 , also decreases. This effect reduces the binding energy of triplet excitons, which favors their dissociation into free charges. Furthermore, the reduction of ΔE ST can contribute to mitigating the losses produced by the nonradiative deactivation of the T 1 excitons. Interestingly, although Cl has a lower electronegativity than F, chlorination is more effective to reduce ΔE ST . Since the chlorination of NFAs is easier than fluorination, Cl substitution can be a useful approach to enhance solar energy harvesting using triplet excitons.

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Section: Materials and Methodsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Binding Energy of Triplet Excitons in Nonfullerene Acceptors: The Effects of Fluorination and Chlorination

et al. 2022

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“…If we loosen restrictions of Δ G S1,CT on the yield of photocharge generation and Δ V nrad , the binary D/A blend simply behaves like the single-component photovoltaic materials. The costs are slower exciton dissociation and higher electric field sensitivity. , …”

Section: Introductionmentioning

confidence: 99%

“…The costs are slower exciton dissociation and higher electric field sensitivity. 16,17 Designing electronic structures of binary materials without the restrictions of ΔG S1,CT gives a boost to the theoretical PCE limit of OSCs. Hence, it attracts intensive studies on the negligible ΔG S1,CT material combinations.…”

Section: Introductionmentioning

confidence: 99%

Reducing the Excitonic Loss at Donor/Acceptor Heterojunction with Negligible Exciton Dissociation Driving Force

Xue

Zhang

et al. 2022

ACS Appl. Energy Mater.

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A breakthrough for non-fullerene acceptors (NFAs) is their efficient photocharge generation and low nonradiative voltage loss (ΔV nrad) in a condition of negligible energy offset (ΔG S1,CT) between the lowest singlet state (S1) and the relaxed charge transfer (CT) state. This inspires the idea of viewing the donor/acceptor (D/A) binary blend as a single component in organic solar cells (OSCs) and attracts tremendous studies on the D/A pairs with negligible ΔG S1,CT. Unfortunately, an arbitrarily chosen material combination usually results in severe photovoltaic performance loss. To solve this problem, we present a diffused heterojunction (DHJ) doping strategy at the D/A heterojunction with small ΔG S1,CT. The electronic doping alleviates the performance loss by accelerating the exciton dissociation rate and reducing the ΔV nrad. After examining the DHJ doping strategy in other six NFA material combinations, we are confident to point out that our work opens an avenue for pursuing intrinsic high OSC performance comparing with other single-component photovoltaic technologies.

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Solid Solvation Assisted Electrical Doping Conserves High‐Performance in 500 nm Active Layer Organic Solar Cells

Xue

Liang

Tang

et al. 2023

Adv Funct Materials

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Organic solar cells (OSCs) process fascinating solution‐printing capability to achieve low‐cost and large‐scale manufacture. However, the rapid power conversion efficiency (PCE) decay with active layer thickness enlargement inhibits the implement of OSCs’ potential advantages. To overcome the bottlenecks of PCE decay in thick active layer OSCs, the electrical doping with componential selectivity in bulk heterojunction (BHJ) film is achieved by introducing a solid solvation additive. Benefiting from the higher exciton splitting efficiency together with the longer drift (Ldr) and diffusion (Ldiff) lengths, an OSC with 100 nm BHJ film demonstrates a PCE increment from 16.44% to 18.24% with prolonged dark and illuminated storage stabilities. Applying the solid solvation assisted (SSA) doping method in the OSCs with 500 nm active layer, the PCE significantly increases by 31.9%, from the original value of 11.79% to 15.55%. It further improves to 15.84% in a ternary blend thick‐film device, which is the record value to the best of our knowledge. Besides, the SSA doping narrows the PCE gap between the 0.04 and 1 cm2 devices. All improvements demonstrate the great potential of SSA doping for OSC commercial manufacture, since it optimizes the photovoltaic performance under all practical conditions of long‐term, thick‐film, and large‐area.

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Conditions for efficient charge generation preceded by energy transfer process in non-fullerene organic solar cells

Abstract: Our results provide a simple relationship involving the driving force and binding energy of CT state to maximize charge generation in non-fullerene organic solar cells.

Cited by 21 publications

References 104 publications

Binding Energy of Triplet Excitons in Nonfullerene Acceptors: The Effects of Fluorination and Chlorination

Binding Energy of Triplet Excitons in Nonfullerene Acceptors: The Effects of Fluorination and Chlorination

Reducing the Excitonic Loss at Donor/Acceptor Heterojunction with Negligible Exciton Dissociation Driving Force

Solid Solvation Assisted Electrical Doping Conserves High‐Performance in 500 nm Active Layer Organic Solar Cells

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