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- Liao, Xunfan, et al.
(författare)
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The role of dipole moment in two fused-ring electron acceptor and one polymer donor based ternary organic solar cells
- 2020
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Ingår i: Materials Chemistry Frontiers. - : Royal Society of Chemistry. - 2052-1537. ; 4:5, s. 1507-1518
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Tidskriftsartikel (refereegranskat)abstract
- Fused-ring electron acceptor (FREA) based ternary organic solar cells (OSCs) have made significant progress and attracted considerable attention due to their simple device architecture and broad absorption range in devices. There are three key parameters that need to be fine-tuned in ternary OSCs including absorption, energy level and morphology in order to realize high efficiencies. Herein, a series of FREAs with diverse electron-rich cores or electron-deficient terminals are developed and rationally combined to achieve high performance ternary OSCs. The dipole moment of FREAs' terminals has been unveiled as an important factor and its working mechanism has been thoroughly investigated by systematically studying six ternary OSCs. These ternary blends all exhibit complementary absorption and cascade energy levels, which can facilitate efficient light-harvesting and charge transfer. Additionally, the morphological effects on ternary OSCs are eliminated through comparative studies while demonstrating distinctively different performance. The preliminary results show that compatible dipole moment between two FREAs is critical in ternary blends. Specifically, the performance of the ternary system with two FREAs having quite different dipole moment terminals is worse compared to that with similar terminal dipole moments. The pair with larger difference in the dipole moment will also negatively impact device performance. This interesting phenomenon is likely due to the fact that very different dipole moments of terminals in FREAs can significantly decrease the electron mobility as well as induce unbalanced hole/electron transport. Consequently, it results in increased charge recombination and reduced charge collection efficiency. This finding demonstrates that the dipole moment of FREAs should be taken into account in designing ternary OSCs.
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| 2. |
- Xu, Guodong, et al.
(författare)
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Reducing Energy Loss and Morphology Optimization Manipulated by Molecular Geometry Engineering for Hetero-junction Organic Solar Cells
- 2020
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Ingår i: Chinese journal of chemistry. - : WILEY-V C H VERLAG GMBH. - 1001-604X .- 1614-7065. ; 38:12, s. 1553-1559
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Tidskriftsartikel (refereegranskat)abstract
- A Summary of main observation and conclusion Molecular geometry engineering is an effective strategy to control the micromorphology and molecular energy level in organic photovoltaics (OPVs). Two novel copolymers based on alkylsilyl- and chloride-functionalized benzodithiophene (BDT) were designed and synthesized for wide bandgap copolymer donor materials in OPVs. It was found that the two copolymers exhibited distinctly different properties in active layer when blended with fullerene-free acceptor IT-4F. The chloride-functionalized copolymer PBDTCl-TZ with deeper molecular energy level and better coplanar structure induced more ordered aggregation in blend film. Thus, the device based on PBDTCl-TZ exhibits better energy alignment with IT-4F and smaller radiative recombination. Furthermore, the non-radiative recombination of PBDTCl-TZ:IT-4F based device is about 45 mV lower than the PBDTSi-TZ:IT-4F based device, contributing to a lower energy loss (E-loss), and a higher open-circut voltage (V-OC). As a result, the devices based on the blend of PBDTCl-TZ:IT-4F exhibit a high power conversion efficiency (PCE) of up to 12.2% with a highV(OC)of 0.837 V, higher than that of PBDTSi-TZ:IT-4F, of which the PCE is 11.2% with a V-OC of 0.781 V.
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