The effect of tuning molecular weight (M n) in poly­[bis­(4-phenyl)­(2,4,6-trimethylphenyl)­amine] (PTAA) to increase both mechanical properties of the film and electrical properties of perovskite solar cells is reported. Perovskite solar cell devices are fabricated to investigate the effect of M n on power conversion efficiency. Moisture stability for various M n is also studied in PTAA films exposed to mechanical loads in humid environments. Furthermore, cohesion and tensile tests are employed to determine the mechanical properties of PTAA, where higher M n leads to more robust films. To elucidate the effect of M n on the debonding kinetics, a viscoelastic fracture kinetic model is proposed as a function of M n, and the debonding mechanism is found to be dependent on M n. Finally, the effect of small-molecule-based dopants on the mechanical stability of PTAA is investigated.

The aggregation in conjugated polyelectrolytes (CPs) can be effectively reduced by the formation of CP/nanoparticle assemblies. The photophysical properties of various nanoassemblies were studied by means of UV-visible and fluorescence spectroscopy in solution and as thin films. The dissociation of the polymer chains is caused by favorable electrostatic interactions between the cationic substituents of the CPs and the anionic charges present on the surface of the nanoparticles. Such an efficient displacement of pi-stacking by competitive positive interactions constitutes the first example of positive aggregation modulation.

Organic thin-film optoelectronic devices, unlike inorganic analogues, offer the attractive prospect of large, flexible, and inexpensive arrays made by simple procedures such as roll-to-roll printing. In current organic thin-film devices, layers of tin-doped indium oxide (ITO) are widely used as electrodes. Motivated by the increasing price of indium and the high cost of ITO-coated substrates, we have examined ways to recover and recycle ITO substrates in typical devices by environmentally benign methods. A process using only water yields recovered ITO substrates that can be reused at least 10 times to prepare new devices without loss of efficiency.

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