## 2 Materials and Methods
### Characterization  
SEM images were taken of DAD films formed using different spin rates and/or different deposition volumes. To achieve all SEM images, an Inspect FEI F50 SEM (Hillsboro, OR, USA) was used with beam spot size and high voltage adjusted to optimize the image quality. The image resolution was generally \(2048\times 1768\) with an imaging speed of 30 \(\upmu\)s. The SEM was calibrated using silicon calibration grids (Bruker model numbers PG: 1 \(\upmu\)m pitch, 110 nm depth and VGRP: 10 \(\upmu\)m pitch, 180 nm depth).  
An issue with SEM imaging of thin films is that unless they exhibit a degree of surface roughness, their presence can often be hard to detect as they will appear visually similar to a bare substrate. To overcome this issue, it was decided to manually damage the film either via light scratching with a scalpel or using the laser beam in a Raman microscopy system. The scalpel will remove any polymer layer present on the surface but will have no effect on the much denser silicon underneath. These scratches were useful for AFM imaging to determine film thickness. In the case of the laser-based removal of material, the laser was focussed on the DAD film producing a spectrum with large silicon peaks accompanied by significant noise interference. Over time, the noise reduced to become negligible. At this point, the laser was stopped as it was interpreted that a clean silicon spectrum indicated that essentially all the DAD in the laser area was burnt from the surface. The laser used to remove material was from a Witec alpha300R Raman microscope (Witec, Ulm, Germany) at an excitation wavelength of 532 nm using a \(\times\)40 objective with a numerical aperture of 0.60. The power level used was to remove material and was the maximum available on the system which was approximately 30 mW.  
Atomic force microscopy (AFM) was performed on solution-processed interlayers on solar device substrates to image the morphology of the films. The thickness of the solution-processed interlayers was measured using AFM by imaging the channels formed in the film with the scalpel, the height of which could be measured from cross sections using the section tool in the analysis software which allows determination of the thickness of the film. Alternatively, thickness could be determined using the depth analysis function in the AFM software and allows an analysis of the height distributions in the images where the level of the substrate and the top of the films could be determined to allow determination of film thickness.  
AFM was performed in air using a Bruker multimode 8 AFM with Nanoscope V controller, operating in standard tapping mode. The AFM probes used were silicon HQNSC15/AlBS Mikromasch probes (nominal tip diameter and spring constant is 16 nm and 40 N m\({}^{-1}\) respectively). Set-point, scan rate, and gain values were chosen to optimize image quality. The AFM scanner was calibrated in x, y, and z directions using silicon calibration grids (Bruker model numbers PG: 1 \(\upmu\)m pitch, 110 nm depth and VGRP: 10 \(\upmu\)m pitch, 180 nm depth). AFM topography images have been flattened and thickness measurements taken using Nanoscope Analysis 1.4.  
Photoelectron spectroscopy in air (PESA) measurements were conducted using an AC-2 photoelectron spectrometer (Riken-Keiki Co., Tokyo, Japan).