Hybrid ZnO Electron Transport Layer by Down Conversion Complexes for Dual Improvements of Photovoltaic and Stable Performances in Polymer Solar Cells

Abstract

Polymer solar cells (PSCs) have shown excellent photovoltaic performance, however, extending the spectral response range to the ultraviolet (UV) region and enhancing the UV light stability remain two challenges to overcome in the development of PSCs. Lanthanide down-conversion materials can absorb the UV light and re-emit it at the visible region that matches well with the absorption of the active layer material PTB7-Th (poly[[2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene][3-fluoro-2[(2-ethylhexyl)carbony]thieno[3,4-b]thiophenediyl]]) and PBDB-T-2F, thus helping to enhance the photovoltaic performance and UV light stability of PSCs. In this research, a down-conversion material Eu(TTA)3phen (ETP) is introduced into the cathode transport layer (ZnO) in PSCs to manipulate its nanostructure morphology for its application in hyperfine structure of PSCs. The device based on the ZnO/ETP electron transport layer can obtain power conversion efficiencies (PCEs) of 9.22% (PTB7-Th–PC71BM ([6,6]-phenylC71-butyric acid methyl ester) device) and 13.12% (PBDB-T-2F–IT-4F device), respectively. Besides, in the research on PTB7-Th-PC71BM device, the stability of the device based on ZnO/ETP layer is prolonged by 70% compared with the ZnO device. The results suggest that the ZnO/ETP layer plays the role of enhanced photovoltaic performance and prolonged device stability, as well as reducing photo-loss and UV degradation for PSCs.

ZnO nanostructured materials for emerging solar cell applications

“…199 Lanthanide down-conversion material, with the ability to absorb UV light and re-emit it in the visible region, was added to the ZnO electron transport layer, so that the re-emitted light matches the absorption energy level of the active layer material. 200 Here, Eu(TTA) 3 phen (ETP) was used as the downconversion material, with PTB7-Th:PC 71 BM as the active layer, resulting in a cell with PCE of 9.22% and 70% higher stability compared to the cell with pristine ZnO. In 2020, Shen et al demonstrated the fabrication of ITO-less solar cells, using oxygen-doped Ag and plasmonic Ag@SiO 2 as a countermeasure for the lack of the ITO layer, taking advantage of both microresonant cavity and plasmonic effect.…”

“…210 The previously mentioned solar cell employing ETP as down-conversion material was also tested using this approach, replacing the PTB7-Th:PC71BM with PBDB-T-2F:IT-4F, increasing its efficiency from 9.22% to 13.12%. 200 Another non-fullerene active layer, PDBD-T-2F:Y6, has been utilized as a BHJ active layer, with the ZnO thin lm as the buffer layer. This time, however, the ligand was also used in the form of tetrahydroxy-perylene bismide (HO-PBI ligand), embedded onto a ZnO thin lm, improving the device efficiency up to 15.73%, making it one of the highest reported nonfullerene based OSCs to date.…”

Organic Eu3+-complex-anchored porous diatomite channels enable UV protection and down conversion in hybrid material

“…Recently, designing visible luminescence materials by lanthanide complexes has attracted increasing attention for various applications [ 15 , 16 ]. Europium(III) ion has abundant energy levels and unique 4 f electronic transitions that result in high-intensity photoluminescence (PL) and efficient quantum yield (Φ tot ) [ 17 ].…”

“…Europium(III) ion has abundant energy levels and unique 4 f electronic transitions that result in high-intensity photoluminescence (PL) and efficient quantum yield (Φ tot ) [ 17 ]. In order to achieve high-intensity PL, 1,10-phenanthroline (Phen) and 2-thenoyltrifluoroacetone (TTA) were introduced as the ligands to produce a complex, Eu(TTA) 3 Phen (ETP), with wide optical absorption [ 16–20 ]. Under UV radiation, this complex absorbs the energy and emits bright red light through relaxing the excited electrons in ligand (TTA) and transferring the energy to Eu(III) ions, which is known as the ‘antenna effect’ [ 17 , 19 , 20 ].…”

“…Under UV radiation, this complex absorbs the energy and emits bright red light through relaxing the excited electrons in ligand (TTA) and transferring the energy to Eu(III) ions, which is known as the ‘antenna effect’ [ 17 , 19 , 20 ]. In addition, the ETP complex has been reported to be an excellent luminescence material absorbing UV-A (315–400 nm) and UV-B (280–315 nm) [ 16 , 17 , 21 ]. Based on the facts mentioned above, ETP was chosen as UV absorber in this work.…”