Constructing Desired Vertical Component Distribution Within a PBDB-T:ITIC-M Photoactive Layer via Fine-Tuning the Surface Free Energy of a Titanium Chelate Cathode Buffer Layer

Abstract

Rationally controlling the vertical component distribution within a photoactive layer is crucial for efficient polymer solar cells (PSCs). Herein, fine-tuning the surface free energy (SFE) of the titanium(IV) oxide bis(2,4-pentanedionate) (TOPD) cathode buffer layer is proposed to achieve a desired perpendicular component distribution for the PBDB-T:ITIC-M photoactive layer. The Owens-Wendt method is adopted to precisely calculate the SFE of TOPD film jointly based on the water contact angle and the diiodomethane contact angle. We find that the SFE of TOPD film increases as the annealing temperature rises, and the subtle SFE change causes the profound vertical component distribution within the bulk region of PBDB-T:ITIC-M. The results of secondary-ion mass spectroscopy visibly demonstrate that the TOPD film with an SFE of 48.71 mJ/cm2, which is very close to that of the ITIC film (43.98 mJ/cm2), tends to form desired vertical component distribution. Consequently, compared with conventional bulk heterojunction devices, the power conversion efficiency increases from 9.00 to 10.20% benefiting from the short circuit current density increase from 14.76 to 16.88 mA/cm2. Our findings confirm that the SFE adjustment is an effective way of constructing the desired vertical component distribution and therefore achieving high-efficiency PSCs.

Nonhalogenated Solvent‐Processed Thick‐Film Ternary Nonfullerene Organic Solar Cells with Power Conversion Efficiency >13% Enabled by a New Wide‐Bandgap Polymer

“…Therefore, γ s was evaluated using the O–W geometric equation method. [ 56–58 ] As shown in the images, the WCAs did not considerably differ. The hydrophobicity demonstrates the efficient charge transport between the active layers due to the effects of the halogenated atoms.…”

Recent progress in cathode interlayer materials for non‐fullerene organic solar cells

“…(C) Three‐dimensional concentration profiles of S 2 − and CN − in the PBDB‐T:ITIC‐M blend films, and the TOPD layer is annealed at 90°C. Reproduced with permission: Copyright 2018, Frontier Media SA 141 (D) Pictures of IT‐4F thin films on glass, glass/ZnO, and glass/SnO 2 substrates under different‐time continuous UV illumination (365 nm, 5 mW cm −2 ).…”

“…It was found that optimum surface free energy (48.7 mJcm −2 ) close to IT‐M can achieve when the annealing temperature of titanium(IV) oxide bis(acetylacetonate) increased to 90°C resulting in the desired face distribution in the active layer based on PBDB‐T:ITIC‐M film which improves the photovoltaic parameters (Voc, Jsc, FF, and PCE) (Figure 6B,C). 141 Shi et al 153 used Ti(i‐OPr) 2 (acac) 2 as CIL in inverted NF‐OSCs. The PCE was increased from 9.6% to 11.7% benefiting from reduced charge recombination.…”

Push-Pull Zinc Porphyrins as Light-Harvesters for Efficient Dye-Sensitized Solar Cells

“…For example, some electron-donating groups in organic sensitizer were successfully applied in porphyrin, such as N-annulated perylene ( 26 in Figure 4 ) (Jiao et al, 2011 ; Luo et al, 2013 , 2016 ), 2-diphenylaminothiophene ( 23 in Figure 4 ) (Wang et al, 2014d ), indoline ( 24 in Figure 4 ) (Pellej et al, 2014 ), phenothiazine ( 31 in Figure 4 ) (Xie et al, 2015 ), and even ferrocene (van der Salm et al, 2015 ). Some concepts from low-band-gap polymer were successfully applied in adjusting the absorption area and energy alignment of the porphyrins, such as weak donor-strong acceptor (Zhou et al, 2012 ; Bai et al, 2018 ; Lin et al, 2018 ; Xie et al, 2018 ), which will be discussed in the following part.…”