Fluidic Manipulating of Printable Zinc Oxide for Flexible Organic Solar Cells

Abstract

As a representative electron transporting layer in organic solar cells, zinc oxide (ZnO) can be fabricated by the meniscus‐guided coating with the promotion of sol–gel technology. In order to fabricate stable and flexible organic solar cells (OSCs) based on the printable ZnO layers, here, a new method for simultaneously manipulating fluidics of the sol–gel ZnO precursor and optimizing processability of the ZnO layer for flexible OSCs is developed. It is found that the Marangoni recirculation in meniscus and the annealing temperature of the sol–gel ZnO precursor can be effectively modulated by changing the Lewis base. With the use of propylamine, the high‐quality ZnO layer that is suitable for flexible OSCs can be fabricated through blade coating. Under such a condition, the formation of polar facet in ZnO layer is well restrained, which favors the photostability of the cells. As a result, the best 1.00 cm2 flexible cell outputs a power conversion efficiency of 16.71%, which is the best value till now.

Hole/Electron Transporting Materials for Nonfullerene Organic Solar Cells

“…[11] Most recently, Hou et al developed a new method of printable ZnO as the ETL for flexible OSCs. [12] They used three amines, ethanolamine (EA), n-propylamine (PA), and triethylamine (TEA), as Lewis base in the precursors to get three types of ZnO (EA-, PA-, and TEA-ZnO) (Figure 2). They showed the morphology of the ZnO film was mainly determined by the recirculation in the liquid wedges.…”

“…Furthermore, the stronger Lewis base led to higher growing draw ratio, higher proportion of valid intermediate in precursor, and lower proportion of the polar facets in final ZnO. [12] As a result, a lower thermal annealing (TA) temperature (130 °C) was needed to convert the PA-based gel into ZnO, making PA-ZnO an ideal candidate to be used as ETL in flexible OSCs.…”

“…(j) The Guinier fitting (solid lines) in low q regions of the SAXS patterns (scatters). Reproduced with permission [12]. Copyright 2022, Wiley-VCH.…”

High‐Efficiency ITO‐Free Organic Photovoltaics with Superior Flexibility and Upscalability

“…Thus, the upscaling of OPVs requires comprehensive optimizations on interface, morphology, and device geometry design. [34,35,37,[39][40][41][42][43][44][45][46][47] Particularly, the interfacial contact has been demonstrated to affect the homogeneity or quality of films and the interfacial resistance, and these effects will be magnified on large scale, as demonstrated by Jeong et al [48] Though with the challenges mentioned above, rapid progress on large-area flexibility has been made. For example, a 1 cm 2 OPV device with 16% efficiency has been built on polyethylene naphthalate/ITO substrates.…”

“…For example, a 1 cm 2 OPV device with 16% efficiency has been built on polyethylene naphthalate/ITO substrates. [42] Unfortunately, the device efficiency dropped by more than 20% even after bending 1 time with a radius of 5 mm, suggesting that the ITO is an inferior transparent electrode for flexible OPVs. For ITO replacement, the Ag NWs have been widely used for large-area flexible OPVs.…”