A long-term operational stability over 1000 hours in the inverted type perovskite solar cells based on the MAPbI ₃ layer is demonstrated under ionic defect-free conditions.

Unlike typical inorganic semiconductors with a crystal structure, the charge dynamics of π-conjugated polymers (π-CPs) are severely limited by the presence of amorphous portions between the ordered crystalline regions. Thus, the formation of interconnected pathways along crystallites of π-CPs is desired to ensure highly efficient charge transport in printable electronics. Here we report the formation of nano-crystallite networks in π-CP films by employing novel template-mediated crystallization (TMC) via polaron formation and electrostatic interaction. The lateral and vertical charge transport of TMC-treated films increased by two orders of magnitude compared with pristine π-CPs. In particular, because of the unprecedented room temperature and solution-processing advantages of our TMC method, we achieve a field-effect mobility of 0.25 cm² V⁻¹ s⁻¹ using a plastic substrate, which corresponds to the highest value reported thus far. Because our findings can be applied to various π-conjugated semiconductors, our approach is universal and is expected to yield high-performance printable electronics.

Processing additives have been widely utilized for high-performance organic bulk-heterojunction (BHJ) photovoltaic devices. However, the role of processing additives remained unclear due to the limited information relying on the final BHJ film state rather than the intermediate film state during solvent evaporation. Here, by using in situ GIWAXS measurements on the intermediate BHJ film, we propose a possible phase separation mechanism in efficient BHJ solar cells consisting of a narrow band gap polymer (P1) and PC₇₁BM via the use of 1-chloronaphthalene (1-CN) as a processing additive. We found that adding small amounts of an additive, 1-CN, with a high boiling point and a high PC₇₁BM solubility can prolong the solvent evaporation time and dissolve many PC₇₁BM molecules, promoting the strong P1 polymer:solvent and PC₇₁BM:solvent interaction to produce pure domains of each component. Thus, the bi-continuous networks for both P1 and PC₇₁BM and their enlarged interfacial area are well fabricated in the BHJ films, inducing balanced photo-charge carrier densities for the electrons and holes and improving the overall photovoltaic performance. Therefore, our findings elucidate the kinetic motions of two organic phases affected by the physical properties of the solvents in the process of film formation and establish criteria for BHJ systems.