| 1. |
- He, Chengliang, et al.
(author)
-
Asymmetric electron acceptor enables highly luminescent organic solar cells with certified efficiency over 18%
- 2022
-
In: Nature Communications. - : NATURE PORTFOLIO. - 2041-1723. ; 13:1
-
Journal article (peer-reviewed)abstract
- Enhancing the luminescence property without sacrificing the charge collection is one key to high-performance organic solar cells (OSCs), while limited by the severe non-radiative charge recombination. Here, we demonstrate efficient OSCs with high luminescence via the design and synthesis of an asymmetric non-fullerene acceptor, BO-5Cl. Blending BO-5Cl with the PM6 donor leads to a record-high electroluminescence external quantum efficiency of 0.1%, which results in a low non-radiative voltage loss of 0.178 eV and a power conversion efficiency (PCE) over 15%. Importantly, incorporating BO-5Cl as the third component into a widely-studied donor:acceptor (D:A) blend, PM6:BO-4Cl, allows device displaying a high certified PCE of 18.2%. Our joint experimental and theoretical studies unveil that more diverse D:A interfacial conformations formed by asymmetric acceptor induce optimized blend interfacial energetics, which contributes to the improved device performance via balancing charge generation and recombination. High-performance organic solar cells call for novel designs of acceptor molecules. Here, He et al. design and synthesize a non-fullerene acceptor with an asymmetric structure for diverse donor:acceptor interfacial conformations and report a certificated power conversion efficiency of 18.2%.
|
|
| 2. |
- He, Chengliang, et al.
(author)
-
Near infrared electron acceptors with a photoresponse beyond 1000 nm for highly efficient organic solar cells
- 2020
-
In: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 8:35, s. 18154-18161
-
Journal article (peer-reviewed)abstract
- Developing near infrared (NIR) organic semiconductors is indispensable for promoting the performance of organic solar cells (OSCs), but addressing the trade-off between voltage and current density thus achieving high efficiency with low energy loss is still an urgent challenge. Herein, NIR acceptors (H1, H2 and H3) with a photoresponse beyond 1000 nm were developed by conjugating dithienopyrrolobenzothiadiazole to 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrileviavaried alkyl thiophene bridges. It was found that the linear outward chains in thiophene bridges could mitigate both the conformation disorder of H3 and the electronic disorder of the PBDB-T:H3 blends, which could help to form a favorable blend morphology, facilitating highly efficient photoelectric conversion in the resultant OSCs. As a result, devices based on PBDB-T:H3 achieve a high efficiency of 13.75% with a low energy loss of 0.55 eV, which is one of the highest efficiencies and the lowest energy loss among OSCs with an optoelectronic response near 1000 nm. This work provides a new design strategy towards NIR acceptors for efficient OSCs and future exploration of functional optoelectronics.
|
|
| 3. |
- Li, Shuixing, et al.
(author)
-
Unveiling structure-performance relationships from multi-scales in non-fullerene organic photovoltaics
- 2021
-
In: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 12:1
-
Journal article (peer-reviewed)abstract
- Unveiling the correlations among molecular structures, morphological characteristics, macroscopic properties and device performances is crucial for developing better photovoltaic materials and achieving higher efficiencies. To achieve this goal, a comprehensive study is performed based on four state-of-the-art non-fullerene acceptors (NFAs), which allows to systematically examine the above-mentioned correlations from different scales. Its found that extending conjugation of NFA shows positive effects on charge separation promotion and non-radiative loss reduction, while asymmetric terminals can maximize benefits from both terminals. Another molecular optimization is from alkyl chain tuning. The shortened alkyl side chain results in strengthened terminal packing and decreased pi-pi distance, which contribute high carrier mobility and finally the high charge collection efficiency. With the most-acquired benefits from molecular structure and macroscopic factors, PM6:BTP-S9-based organic photovoltaics (OPVs) exhibit the optimal efficiency of 17.56% (certified: 17.4%) with a high fill factor of 78.44%, representing the best among asymmetric acceptor based OPVs. This work provides insight into the structure-performance relationships, and paves the way toward high-performance OPVs via molecular design. Understanding correlations between molecular structures and macroscopic properties is critical in realising highly efficient organic photovoltaics. Here, the authors conduct a comprehensive study based on four non-fullerene acceptors revealing how the extended conjugation, asymmetric terminals and alkyl chain length can affect device performance.
|
|
| 4. |
- Li, Yaokai, et al.
(author)
-
Mechanism study on organic ternary photovoltaics with 18.3% certified efficiency: from molecule to device
- 2022
-
In: Energy & Environmental Science. - : ROYAL SOC CHEMISTRY. - 1754-5692 .- 1754-5706. ; 15:2, s. 855-865
-
Journal article (peer-reviewed)abstract
- Multi-component organic photovoltaics (OPVs), e.g., ternary blends, are effective for high performance, while the fundamental understanding from the molecular to device level is lacking. To address this issue, we here systematically study the working mechanism of ternary OPVs based on non-fullerene acceptors (NFAs). With both molecular dynamics simulations and morphology characterization, we identify that when adding another larger band gap and highly miscible NFA, namely IT-4F or BTP-S2, into the PBDB-TF:BTP-eC9 blend, the NFAs undergo molecular intermixing selectively with BTP-eC9. This causes the composition-dependent band gap and charge recombination, and hence the composition-dependent V-OC. While the charge recombination still dominantly occurs at the PBDB-TF:BTP-eC9 interface, BTP-S2 or IT-4F plays an auxiliary role in facilitating charge transfer and suppressing non-radiative decay. Interestingly, intermolecular end-group packing in the intermixed blend is improved compared to that in pristine films, leading to higher carrier mobility. These synergistic effects significantly improve the power conversion efficiency of the device to an outstanding value of 18.7% (certified value of 18.3%).
|
|
| 5. |
- Wang, Chengliang, et al.
(author)
-
Hybrid-cavity fabry-perot interferometer for multi-point relative humidity and temperature sensing
- 2018
-
In: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 255, s. 1937-1944
-
Journal article (peer-reviewed)abstract
- A novel hybrid-cavity Fabry-Perot interferometer (HFPI) is theoretically proposed and experimentally demonstrated. The hybrid micro-cavity structure is consisted of a short segment of four-hole suspended-core fiber (SCF) and attaching moderate optical adhesive as the hygroscopic material. Due to the different sensitivities of the hybrid Fabry-Perot (F-P) cavities to the relative humidity (RH) and temperature, both information can be simultaneously demodulated by utilizing the phase-shift tracking scheme in the Fast Fourier Transform (FFT) spectra. The precise micromanipulation of each cavity length ensures the separation of each amplitude peak in the FFT spectra, which renders this HFPI multi-point sensing capability. Experimental tests were carried out, and the results indicate that the proposed HFPI with excellent sensing performance is a promising platform for multi-point RH and temperature sensing applications.
|
|
| 6. |
- Xia, Xinxin, et al.
(author)
-
Revealing the crystalline packing structure of Y6 in the active layer of organic solar cells: the critical role of solvent additives
- 2023
-
In: Journal of Materials Chemistry A. - : ROYAL SOC CHEMISTRY. - 2050-7488 .- 2050-7496. ; 11:40, s. 21895-21907
-
Journal article (peer-reviewed)abstract
- The bulk heterojunction (BHJ) morphology of photovoltaic materials is crucial to the fundamental optoelectronic properties of organic solar cells (OSCs). However, in the photoactive layer, the intrinsic crystalline packing structure of Y6, currently the hallmark molecule among Y-series non-fullerene acceptors (NFAs), has not been unambiguously determined. Here, employing grazing-incidence wide-angle X-ray scattering (GIWAXS), we managed to uncover the intrinsic crystalline packing structure of Y6 in the BHJ active layer of OSCs, which is found to be different from its single-crystal structure reported previously. Moreover, we find that solvent additive 1-chloronaphthalene (CN) can induce highly ordered packing of Y6 in BHJ thin films. With the help of atomistic molecular dynamics simulations, it is revealed that pi-pi interactions generally exist between naphthalene derivatives and IC terminals of Y6 analogues, which would essentially improve their long-range ordering. Our work reveals the intrinsic crystalline packing structure of Y6 in the BHJ active layer as well as its crystallization mechanism in thin films, thus providing direct correlations between this crystalline packing and the device characteristics and photophysical properties.
|
|
