| 1. |
- Luo, Zhenghui, et al.
(author)
-
Fine-Tuning Energy Levels via Asymmetric End Groups Enables Polymer Solar Cells with Efficiencies over 17%
- 2020
-
In: Joule. - : CELL PRESS. - 2542-4351. ; 4:6, s. 1236-1247
-
Journal article (peer-reviewed)abstract
- Generally, it is important to fine-tune the energy levels of donor and acceptor materials in the field of polymer solar cell (PSCs) to achieve a minimal highest occupied molecular orbital (HOMO) energy offset, which yet is still sufficient for charge separation. Based on the high-performance small-molecule acceptor (SMA) of BTP-4F, we modified the end groups of BTP-4F from IC-2F to CPTCN-Cl. It was found that when both end groups were substituted by CPTCN-Cl, the energy level upshift was too large that caused unfavorable energetic alignment, thus poor device performance. By using the strategy of asymmetric end groups, we were able to achieve near optimal energy level match, resulting in higher open-circuit voltage (V-OC) and power conversion efficiency (PCE) compared with those given by the PM6:BTP-4F system. Our strategy can be useful and potentially applied to othermaterial systems for maximizing efficiency of non-fullerene PSCs.
|
|
| 2. |
- Ma, Ruijie, et al.
(author)
-
Adding a Third Component with Reduced Miscibility and Higher LUMO Level Enables Efficient Ternary Organic Solar Cells
- 2020
-
In: ACS Energy Letters. - : American Chemical Society (ACS). - 2380-8195. ; 5:8, s. 2711-2720
-
Journal article (peer-reviewed)abstract
- It is widely known that the miscibility between donor and acceptor is a crucial factor that affects the morphology and thus device performance of nonfullerene organic solar cells (OSCs). In this Letter, we show that incorporating a third component with lower miscibility and higher lowest unoccupied molecular orbital (LUMO) level into the state-of-the-art PM6:Y6 system can significantly enhance the performance of devices. The best results of the ternary devices are achieved by adding a small molecular acceptor named ITCPTC (similar to 5% w/w), which significantly improves the power conversion efficiency (PCE) of the host system from 16.44% to 17.42%. The higher LUMO of the third component increases the open-circuit voltage (V-oc), while the low miscibility enlarges the domains and leads to improved short-circuit current density (J(sc)) and fill factor (FF). The efficacy of this strategy is supported by using other nonfullerene third components including an asymmetric small molecule (N7IT) and a polymer acceptor (PF2-DTC), which play the same role as ITCPTC and boost the PCEs to 16.96% and 17.04%, respectively. Our approach can be potentially applied to a wide range of OSC material systems and should facilitate the development of the OSC field.
|
|
| 3. |
- Sun, Huiliang, et al.
(author)
-
A Narrow-Bandgap n-Type Polymer with an Acceptor-Acceptor Backbone Enabling Efficient All-Polymer Solar Cells
- 2020
-
In: Advanced Materials. - : WILEY-V C H VERLAG GMBH. - 0935-9648 .- 1521-4095. ; 32
-
Journal article (peer-reviewed)abstract
- Narrow-bandgap polymer semiconductors are essential for advancing the development of organic solar cells. Here, a new narrow-bandgap polymer acceptor L14, featuring an acceptor-acceptor (A-A) type backbone, is synthesized by copolymerizing a dibrominated fused-ring electron acceptor (FREA) with distannylated bithiophene imide. Combining the advantages of both the FREA and the A-A polymer, L14 not only shows a narrow bandgap and high absorption coefficient, but also low-lying frontier molecular orbital (FMO) levels. Such FMO levels yield improved electron transfer character, but unexpectedly, without sacrificing open-circuit voltage (V-oc), which is attributed to a small nonradiative recombination loss (E-loss,E-nr) of 0.22 eV. Benefiting from the improved photocurrent along with the high fill factor andV(oc), an excellent efficiency of 14.3% is achieved, which is among the highest values for all-polymer solar cells (all-PSCs). The results demonstrate the superiority of narrow-bandgap A-A type polymers for improving all-PSC performance and pave a way toward developing high-performance polymer acceptors for all-PSCs.
|
|
| 4. |
- Sun, Huiliang, et al.
(author)
-
Reducing energy loss via tuning energy levels of polymer acceptors for efficient all-polymer solar cells
- 2020
-
In: Science China Chemistry. - : Springer Science and Business Media LLC. - 1869-1870 .- 1674-7291. ; 63:12, s. 1785-1792
-
Journal article (peer-reviewed)abstract
- The open-circuit voltage (Voc) of all-polymer solar cells (all-PSCs) is typically lower than 0.9 V even for the most efficient ones. Large energy loss is the main reason for limiting Voc and efficiency of all-PSCs. Herein, through materials design using electron deficient building blocks based on bithiophene imides, the lowest unoccupied molecular orbital (LUMO) energy levels of polymer acceptors can be effectively tuned, which resulted in a reduced energy loss induced by charge generation and recombination loss due to the suppressed charge-transfer (CT) state absorption. Despite a negligible driving force, all-PSC based on the polymer donor and acceptor combination with well-aligned energy levels exhibited efficient charge transfer and achieved an external quantum efficiency over 10% while maintaining a large Voc of 1.02 V, leading to a 9.21% efficiency. Through various spectroscopy approaches, this work sheds light on the mechanism of energy loss in all-PSCs, which paves an avenue to achieving efficient all-PSCs with large Voc and drives the further development of all-PSCs.
|
|
| 5. |
- Sun, Huiliang, et al.
(author)
-
Reducing energy lossviatuning energy levels of polymer acceptors for efficient all-polymer solar cells
- 2020
-
In: Science China Chemistry. - : Science China Press and Springer-Verlag GmbH Germany. - 1674-7291 .- 1869-1870. ; 63, s. 1785-1792
-
Journal article (peer-reviewed)abstract
- The open-circuit voltage (V-oc) of all-polymer solar cells (all-PSCs) is typically lower than 0.9 V even for the most efficient ones. Large energy loss is the main reason for limitingV(oc)and efficiency of all-PSCs. Herein, through materials design using electron deficient building blocks based on bithiophene imides, the lowest unoccupied molecular orbital (LUMO) energy levels of polymer acceptors can be effectively tuned, which resulted in a reduced energy loss induced by charge generation and recombination loss due to the suppressed charge-transfer (CT) state absorption. Despite a negligible driving force, all-PSC based on the polymer donor and acceptor combination with well-aligned energy levels exhibited efficient charge transfer and achieved an external quantum efficiency over 10% while maintaining a largeV(oc)of 1.02 V, leading to a 9.21% efficiency. Through various spectroscopy approaches, this work sheds light on the mechanism of energy loss in all-PSCs, which paves an avenue to achieving efficient all-PSCs with largeV(oc)and drives the further development of all-PSCs.
|
|
| 6. |
- Tang, Yumin, et al.
(author)
-
Two Compatible Polymer Donors Enabling Ternary Organic Solar Cells with a Small Nonradiative Energy Loss and Broad Composition Tolerance
- 2020
-
In: Solar RRL. - : Wiley-VCH Verlagsgesellschaft. - 2367-198X. ; 4:11
-
Journal article (peer-reviewed)abstract
- High-performance nonfullerene ternary organic solar cells (OSCs) with two polymer donors are less frequently reported because of the limited numbers of efficient polymer donors with good compatibility. Herein, a wide-bandgap polymer P1 with a deep-lying highest occupied molecular orbital (HOMO) level is incorporated as the third component into the benchmark PM6:Y6 binary system to fabricate ternary OSCs. The introduction of P1 not only leads to extended absorption coverage and forms a cascade-like energy level alignment but also shows excellent compatibility with PM6, resulting in a favorable morphology in the ternary blend. More importantly, P1 possesses a deeper HOMO level (-5.6 eV) than most well-known donor polymers, which enables resulting ternary OSCs with an improved open-circuit voltage. As a result, the optimized ternary OSCs with 40 wt% P1 in donors achieve a power conversion efficiency (PCE) of 16.2% with a small nonradiative recombination loss of 0.23 eV, which is among the highest values of ternary OSCs based on two polymer donors. In addition, the ternary OSCs show a broad composition tolerance with a high PCE of over 14% throughout the whole blend ratios. These results provide an effective approach to fabricate efficient ternary OSCs by synergizing two wide-bandgap polymer donors.
|
|
| 7. |
- Yao, Huatong, et al.
(author)
-
All-Polymer Solar Cells with over 12% Efficiency and a Small Voltage Loss Enabled by a Polymer Acceptor Based on an Extended Fused Ring Core
- 2020
-
In: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840. ; 10
-
Journal article (peer-reviewed)abstract
- Although the field of all-polymer solar cells (all-PSCs) has seen rapid progress in device efficiencies during the past few years, there are limited choices of polymer acceptors that exhibit strong absorption in the near-IR region and achieve high open-circuit voltage (V-OC) at the same time. In this paper, an all-PSC device is demonstrated with a 12.06% efficiency based on a new polymer acceptor (named PT-IDTTIC) that exhibits strong absorption (maximum absorption coefficient: 2.41 x 10(5)cm(-1)) and a narrow optical bandgap (1.49 eV). Compared to previously reported polymer acceptors such as those based on the indacenodithiophene (IDT) core, the indacenodithienothiophene (IDTT) core has further extended fused ring, providing the polymer with extended absorption into the near-IR region and also increases the electron mobility of the polymer. By blending PT-IDTTIC with the donor polymer, PM6, a high-efficiency all-PSC is achieved with a small voltage loss of 0.52 V, without sacrificingJ(SC)and FF, which demonstrates the great potential of high-performance all-PSCs.
|
|
