This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record . Please cite this article as doi: 10.1002/solr.201900120 This article is protected by copyright. All rights reserved Enhanced Stability and Optimized Morphology Induced by Electric Field Assisted Annealing of Bulk Heterojunction Solar Cells Raaghesh Vijayan, Abdul Azeez, and K.S. Narayan* Raaghesh Vijayan, Abdul Azeez, and Prof. K.S. Narayan Chemistry and Physics of Materials Unit (CPMU), School of Advanced Materials (SAMat), Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, P.O., Jakkur, Bengaluru 560064, India. Email: narayan@jncasr.ac.in Keywords: Organic solar cells, stability, vertical phase segregation, electric-field assisted annealing, noise spectroscopy Abstract: The utility of electric field during the bulk heterojunction (BHJ) film drying process for tuning the morphology and stability of the device is demonstrated. An external electric field assisted annealing (EFTA) treatment is used to engineer stability of amorphous donor polymer based BHJs without compromising the device performance. Residual additive in the device post fabrication is a major source for degradation. Thermal annealing of active layer has shown to effectively remove residual additive, which in case of amorphous polymer donor based BHJs however leads to unfavourable change in morphology. The detrimental effect of thermal annealing in amorphous donor polymer based solar cells is mitigated by the Accepted Article h h Vijayan, Ab Vijayan, A y and Physics nd Phys al Nehru Cent al Nehru C ndia ia. arayan@jncas arayan@jn A s: Organic so s: Organic g, noise spectr oise spe ty of electric of elect e morphology orphol annealing nealing (E based BHJs sed BHJ w ost ost fabrication fabric wn to effectiv effec