Nanoscale characterization of squaraine-fullerene-based photovoltaic active layers by atomic force microscopy mechanical and electrical property mapping

Nanoscale Polarization‐Resolved Surface Photovoltage of a Pleochroic Squaraine Thin Film

“…Such a layered architecture is accessible via self‐assembly only because there are no orthogonal solvents for SQIB and PCBM available to facilitate subsequent spincoating steps. Such a bilayer design contrasts the separation into small intermixed domains for modest annealing temperatures typically anticipated for conventional bulk‐heterojunction solar cells …”

Measurement and Theoretical Interpretation of Exciton Diffusion as a Function of Intermolecular Separation for Squaraines Targeted for Bulk Heterojunction Solar Cells

“…Our recent work shows how short-range ICT coupling and long-range Coulombic coupling are influenced by sample morphology and phase separation, driven by chemical compatibility between SQ and fullerene and control of crystallinity in thin films either upon spin-casting or after subsequent annealing treatment. 35 As stated above, increased exciton diffusion rates and charge mobility, and thus improved PCE, are expected to result from highly crystalline SQ films. 36,37 However, our work also expressed the need to maintain small domain sizes 21,24 when exciton diffusion lengths are intrinsically small, and we also recognize in our data that some degree of aggregate disruption may actually lead to an increase in overall PCE.…”

Nano-films of carbo-benzene derivatives: Scanning probe microscopy analysis and prospects of use in organic solar cells

“…For instance, STM has been used for imaging the process of selfassembled molecular systems, revealing the parameters involved in monolayer formation: physical parameters (i.e., concentration of solutes, wettability, contact angles, surface tension, temperature) and chemical parameters (i.e., molecular structure, orbital configuration) [3]. On the other hand, AFM is regularly used to characterize morphology of the bulk heterojunction (BHJ) blend in organic solar cells (OSCs) [4]. Besides AFM surface topography measurements, various electrical modes of AFM, such as Kelvin probe force microscopy (KPFM) and conductive-AFM (c-AFM), play an increasing role in understanding the influence of the nanoscale morphology of optoelectronics devices [4].…”

“…On the other hand, AFM is regularly used to characterize morphology of the bulk heterojunction (BHJ) blend in organic solar cells (OSCs) [4]. Besides AFM surface topography measurements, various electrical modes of AFM, such as Kelvin probe force microscopy (KPFM) and conductive-AFM (c-AFM), play an increasing role in understanding the influence of the nanoscale morphology of optoelectronics devices [4]. J. Lee et al [5], used KPFM to study the internal potential distribution of the PCDTBT:PCBM-based OSCs active film, demonstrating the usefulness of this non-invasive approach for quantifying and mapping local differences in electrical performance due to structural heterogeneities.…”