Solution-processable n-doped graphene-containing cathode interfacial materials for high-performance organic solar cells

Pan, Fei; Sun, Chenkai; Li, Yingfen; Tang, Dianyong; Zou, Yingping; Li, Xiaojun; Bai, Song; Wei, Xian; Lv, Menglan; Chen, Xiwen; Li, Yongfang

doi:10.1039/c9ee02433f

Cited by 140 publications

(91 citation statements)

References 54 publications

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“…However, the progress of conventional binary configuration has lagged behind that of ternary counterpart (Table S1, Supporting Information), albeit with additional advantage of easier manufacture process for OSCs . To date, the best efficiency reported based on binary configuration is 16.4%, which apparently deserves more efforts for further improvement …”

Section: Detailed Photovoltaic Parameters Of Devices Employing Pm6:y6mentioning

confidence: 99%

Graphdiyne Derivative as Multifunctional Solid Additive in Binary Organic Solar Cells with 17.3% Efficiency and High Reproductivity

et al. 2020

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Morphology tuning of the blend film in organic solar cells (OSCs) is a key approach to improve device efficiencies. Among various strategies, solid additive is proposed as a simple and new way to enable morphology tuning. However, there exist few solid additives reported to meet such expectations. Herein, chlorine‐functionalized graphdiyne (GCl) is successfully applied as a multifunctional solid additive to fine‐tune the morphology and improve device efficiency as well as reproductivity for the first time. Compared with 15.6% efficiency for control devices, a record high efficiency of 17.3% with the certified one of 17.1% is obtained along with the simultaneous increase of short‐circuit current (Jsc) and fill factor (FF), displaying the state‐of‐the‐art binary organic solar cells at present. The redshift of the film absorption, enhanced crystallinity, prominent phase separation, improved mobility, and decreased charge recombination synergistically account for the increase of Jsc and FF after introducing GCl into the blend film. Moreover, the addition of GCl dramatically reduces batch‐to‐batch variations benefiting mass production owing to the nonvolatile property of GCl. All these results confirm the efficacy of GCl to enhance device performance, demonstrating a promising application of GCl as a multifunctional solid additive in the field of OSCs.

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Section: Detailed Photovoltaic Parameters Of Devices Employing Pm6:y6mentioning

confidence: 99%

Graphdiyne Derivative as Multifunctional Solid Additive in Binary Organic Solar Cells with 17.3% Efficiency and High Reproductivity

et al. 2020

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“…246 Interfacial modification has been done in different thin-film photovoltaic cells. 114,248 In PSCs, engineering of the interface between different layers of the device, including the interface between the LHP film and ESL (metal oxides or other organics in planar PSCs or scaffold layer in mesoporous devices), LHP layer and HSL, and HSL and metal contact is critical for long-term stability of devices.…”

Section: Interfaces Between the Layersmentioning

confidence: 99%

The role of carbon-based materials in enhancing the stability of perovskite solar cells

Hadadian

Smått

Correa‐Baena

2020

Energy Environ. Sci.

178

113

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“…Combined with the wide‐bandgap polymer donor PBDB‐T or its fluorinated derivative PM6 (both having a high vertical E T1 of ≈1.70 eV), these acceptors achieved the highest PCEs of 11.2% for PBDB‐T:ITIC, 14.6% for PM6:IT‐4F, and 16.5% for PM6:Y6, and the Δ E CT in the corresponding devices were measured to be 0.18, 0.22, and 0.07 eV, respectively. [ 29,31,32,60,61 ] By making the difference between Δ E ST and Δ E CT , the Δ E BET for the three OPVs are derived to be 0.22, 0.13, and 0.23 eV, respectively. Then the rates of T1 back to T CT ( k T1 → CT ) can be estimated to be 10 7 –10 9 s −1 according to the Marcus−Levich−Jortner theory and other typical parameters (see the details in Supporting Information).…”

Section: Figurementioning

confidence: 99%

“…This is also beneficial to achieve high FFs (75‐80%) even under moderate charge mobilities of ≈10 −4 cm 2 V −1 s −1 . [ 29,32,60 ]…”

Section: Figurementioning

confidence: 99%

Reducing the Singlet−Triplet Energy Gap by End‐Group π−π Stacking Toward High‐Efficiency Organic Photovoltaics

2020

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S CT) or triplet ( T CT) character in a 1:3 ratio following the spin statistics. [8] These nearly energetically degenerate S CT and T CT excitons will recombine or separate again into FC. The recombination of S CT to the ground state (S0) can be effectively suppressed because of the high enough S CT energy (E CT ), according to the energygap law ( Figure S1a, Supporting Information). [9−12] Although the recombination from T CT to S0 is spin-forbidden, T CT can relax to the lower-lying triplet state (T1) on the material with lower S1 excitation energy (E S1 , which determines optical gap of the device, E g ) via back electron transfer (BET). [13−18] The singlet−triplet energy gap (ΔE ST = E S1 -E T1 , where E T1 is the T1 excitation energy) is usually very large (≈0.7 eV) in the organic π-conjugated molecules and polymers with strong optical absorption and emission. [19−21] If the CT driving force (ΔE CT = E S1 -E CT ) is small (as required to maximize open-circuit voltage, V OC ), the speed of T1 to thermalize back into T CT will be limited due to the large difference between E CT and E T1 (ΔE BET = E CT -E T1 , Figure S1b, Supporting Information); the decay of T1 to S0 via intersystem crossing (ISC) and tripletcharge annihilation can thus constitute a major terminal loss channel of photocurrent. [13−18] Therefore, in order to reduce both voltage loss and NG recombination, the ΔE ST needs to be minimized ( Figure 1b). [22,23] Here, we have investigated the critical role of end-group π−π stacking in reducing ΔE ST in the state-of-the-art narrowbandgap nonfullerene (NF) acceptors (ITIC, IT-4F, and Y6, [24−26] Figure 2a) by means of (time-dependent) density functional theory (TD)DFT calculations in combination with molecular dynamics (MD) simulations (see Supporting Information for details). Owing to a modest degree of intramolecular push−pull effect, these acceptors show moderate ΔE ST while large oscillator strength ( f, ≈3) in the isolated molecules. Importantly, the ΔE ST is further reduced to 0.3−0.4 eV in the end-group π−π stacking dimers that are frequently present in the films. Such small ΔE ST proves to be able to suppress the T1 decay even in the case of very low ΔE CT of 0.1−0.2 eV. Accordingly, high J SC (>20 mA cm −2 ) and fill factor (FF, 75-80%) as well as low ΔV OC (≈ 0.6 V) have been achieved simultaneously, leading to high power conversion efficiencies (PCEs) of 13-18% in the OPVs based on these acceptors. [25−40] In principle, the ΔE ST value is determined by the electron exchange energy. Normally, the S1 and T1 states are both To improve the power conversion efficiencies for organic solar cells, it is necessary to enhance light absorption and reduce energy loss simultaneously. Both the lowest singlet (S1) and triplet (T1) excited states need to energertically approach the charge-transfer state to reduce the energy loss in exciton dissociation and by triplet recombination. Meanwhile, the S1 energy needs to be decreased to broaden light absorption. Therefore, it is imperative to reduce the...

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Solution-processable n-doped graphene-containing cathode interfacial materials for high-performance organic solar cells

Abstract: Solution-processable n-doped graphene-containing cathode interfacial material with a low work function demonstrates 16.52% power conversion efficiency in organic solar cells.

Cited by 140 publications

References 54 publications

Graphdiyne Derivative as Multifunctional Solid Additive in Binary Organic Solar Cells with 17.3% Efficiency and High Reproductivity

Graphdiyne Derivative as Multifunctional Solid Additive in Binary Organic Solar Cells with 17.3% Efficiency and High Reproductivity

The role of carbon-based materials in enhancing the stability of perovskite solar cells

Reducing the Singlet−Triplet Energy Gap by End‐Group π−π Stacking Toward High‐Efficiency Organic Photovoltaics

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