Degradation in organic solar cells: A quantitative analysis

International Conference and Exhibition on Mesoscopic & Condensed Matter Physics

June 22-24, 2015 Boston, USA

Swati Arora

University of Delhi, India

Posters-Accepted Abstracts: J Material Sci Eng

Abstract :

Tremendous efforts have been made in improving the efficiency of organic solar cells; however, a systematic study to stabilize the solar cells still remains the need of the hour. The solar cells of ITO/PEDOT: PSS/Active layer/Al were fabricated and studied. The cell performance not only depended on the device architecture, but lowering of VOC and JSC with time could also be co-related with the shift in energy levels of active layer and work function of Al and ITO electrodes. The theoretical modelling to fit the experimental results indicated that as time passes, the activity at the electrode junctions becomes important and the junctions deteriorate. Thus, the interfaces start playing a dominant role leading to creation of new interface states (increase in density of states from 9Ã?Â?1011 to 1Ã?Â?1013 cm-2eV-1), increase in thickness of interface layer from 8 Ã?Â? to 13 Ã?Â?, and change in HOMO-LUMO levels of active layer. Lowering of mobility (from ~ 10-5 to 1Ã?Â?10-7 cm2V-1s-1) and carrier lifetime was also responsible for degradation. The hole extracting layer, PEDOT: PSS, was incorporated with MWCNT to improve the efficiency. Though the conductivity of PEDOT: PSS increased by an order of magnitude, but similar degradation patterns were observed as was for pristine solar cell. Degradation of PEDOT:PSS is mainly due to hygroscopic PSS. Therefore, the devices kept in vacuum and nitrogen gas environment showed better stability, i.e., approximately 80%, 50% and 40% fall in initial efficiency, respectively for devices kept in air, vacuum and nitrogen gas. MWCNT in the active layer (P3HT: PCBM) stabilizes the cell performance in contrast to pristine cell by ~ 20%. Further, PCDTBT: PCBM based solar cells were also investigated for stability and lifetime studies.

Biography :

Swati Arora did her PhD in thin films photovoltaic solar cells from University of Delhi in 1991, and is presently working as Associate Professor in University of Delhi. She has about 30 years of research experience. She was also associated with teaching and research work at EIT (Africa) and was Editor-in-Chief for the “Science Vision magazine” for popularization of science there. She has published a number of research papers in the International Journals/Conferences and is a part of several research projects. Her major field of interest is thin films solar cells and their degradation studies.

Email: drswatia@yahoo.com