Circumventing UV Light Induced Nanomorphology Disorder to Achieve Long Lifetime PTB7-Th:PCBM Based Solar Cells

5 years ago

Circumventing UV Light Induced Nanomorphology Disorder to Achieve Long Lifetime PTB7-Th:PCBM Based Solar Cells

Quan Liu, Feng Liu, Thomas P. Russell, Miguel Montes Bajo, Jordi Martorell, Paola Mantilla-Perez, Johann Toudert

Large area flexible electronics rely on organic or hybrid materials prone to degradation limiting the device lifetime. For many years, photo-oxidation has been thought to be one of the major degradation pathways. However, intense illumination may lead to a burn-in or a rapid decrease in performance for devices completely isolated from corrosive elements as oxygen or moisture. The experimental studies which are presented in here indicate that a plausible triggering for the burn-in is a spin flip after a UV photon absorption leading to the accumulation of electrostatic potential energy that initiates a rapid destruction of the nanomorpholgy in the fullerene phase of a polymer cell. To circumvent this and achieve highly stable and efficient devices, a robust nanocrystalline ordering is induced in the PCBM phase prior to UV illumination. In that event, PTB7-Th:PC71BM cells are shown to exhibit T80 lifetimes larger than 1.6 years under a continuous UV-filtered 1-sun illumination, equivalent to 7 years for sunlight harvesting at optimal orientation and 10 years for vertical applications. In polymer cells, a spin flip at the donor/acceptor interface after the absorption of high energy photons leads to the accumulation of electrostatic potential energy initiating a rapid destruction of the fullerene nanomorpholgy. By inducing a robust nanocrystalline ordering in the fullerene phase, PTB7-Th cells with high efficiency (≈9%) and long lifetime (>7 and >10 years for optimal and vertical orientations, respectively) are fabricated.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/aenm.201701201