Enhancing Performance of Inverted Organic Solar Cells by　Nano-imprinting the Active Layer with a PDMS Template

摘要

The potential applications of organic materials in solar cells have been widely explored for the creation of inexpensiveand flexible modules compared with their inorganic counterparts. However, the power conversion efficiency (PCE) oforganic solar cells (OSCs) have been severely restricted on account of the insufficient light absorption in the organicactive layers. A simple method to achieve higher absorption efficiency is to increase the thickness of the active layer, butconsiderable electrical loss can occur during charge transport to the electrodes. Therefore, it is necessary to seek someeffective ways to enhance light absorption in active layer without increasing its thickness. OSCs with invertedconfiguration usually present higher PCE and longer lifetime than corresponding devices with regular configuration. Inthis study, we demonstrate an improvement in photovoltaic properties in inverted OSCs by introducing the patternedstructures in the active layer (PTB7:PC_(70)BM) using a nano-imprinting technique with a PDMS stamp. By adjustingpressure of imprinting the active layer, the imprinted OSCs were optimized, showing the optimal optoelectronicperformances. The results indicated when the imprinted cell was pressed by a 200 g weight, the absorption of the nanoimprintedcell dramatically increased compared with the control cell. Meanwhile, the fill factor (FF) also increased from68.0% for the control to 70.0% for the optimal imprinted cell. In addition, the open voltage (V_(oc)) was maintained in 0.73V. Overall, the PCE of 6.95% with a 6.0% enhancement compared to the control cell (6.54%) was achieved.