Conjugated Polymer Nanowire-Based Bulk Heterojunction Solar Cells: Morphology and Photovoltaic Properties

摘要

Organic solar cells have shown great promises as a low-cost, flexible alternative to conventional inorganic solar cells, and bulk heterojunction solar cells have been the most studied organic solar cell architecture. However, because photogenerated excitons in polymer solar cells have relatively small diffusion lengths (5?20 nm), the active layer of bulk heterojunction (BHJ) cells must be structured on the same scale as the exciton diffusion length to achieve high power conversion efficiency (PCE). Our group has reported the use of self-assembled polymer semiconductor nanowires (NWs) in organic solar cells, and enhanced photovoltaic properties have been observed. For example, highly crystalline NWs of ca. 8?30 nm widths, 3?5 nm thickness, and lengths of up to 1?10 μm have been assembled from solutions of poly(3-butylthiophene) (P3BT), and exploited in the construction of efficient BHJ solar cells. Although the width and thickness of self- assembled NWs of poly(3-alkylthiophene)s fall in the range comparable to the exciton diffusion length, an understanding of how the NW length and thus aspect ratio (length/width) affects the photovoltaic efficiency of polymer-semiconductor NW-based solar cells is still missing. Here, we use diblock copolymer semiconductors to explore the control of NW aspect ratio and the effect of aspect ratio on the photovoltaic properties of polymer NWs/fullerene solar cells.