Abstract
In this study, a new type of low-bandgap small molecule has been synthesized with a thieno[3,4-c]pyrrole-4,6-dione (TPD) derivative for application in bulk heterojunction (BJH) solar cells. The series of solar cells were fabricated by blending the TPD-based small molecule (M1) and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM). In order to optimize the performance of solar cells, the nanoscale morphologies of the BHJ layers were controlled via processing additives with 1,8-diiodooctane (DIO) and 1-chloronaphthalene (CN). Therefore, we demonstrated that the use of CN successively suppressed molecular aggregation and demonstrated suitable phase separation, in addition to increasing the power conversion efficiency from 0.36% to 1.86%.
Highlights
Solution-processed organic solar cells have been studied due to the social demand of low-cost, lightweight, flexible, and printable devices in large scale [1,2,3,4,5]
Significant progress of organic solar cells has been demonstrated by utilizing a bulk heterojunction (BHJ) strategy consisting of narrow-bandgap conjugated polymers as p-type semiconductors and fullerene derivatives as n-type semiconductors, [6,7,8,9,10,11,12,13] leading to desirable, nanoscale phase separation of the two organic components and the achievement of a high power conversion efficiency (PCE) [14,15,16,17]
In order to optimize such a BHJ solar cell system, many efforts have been mainly focused on developing novel, p-type conjugated polymers because of their unique light-harvesting properties, good film formation, and extended electron delocalization through their backbone structures synthesized by alternative copolymerization with electron donor (D) and acceptor (A) units, which can lead to good charge carrier mobilities and narrow energy band gaps [18,19,20,21,22,23,24]
Summary
Solution-processed organic solar cells have been studied due to the social demand of low-cost, lightweight, flexible, and printable devices in large scale [1,2,3,4,5]. In order to optimize such a BHJ solar cell system, many efforts have been mainly focused on developing novel, p-type conjugated polymers because of their unique light-harvesting properties, good film formation, and extended electron delocalization through their backbone structures synthesized by alternative copolymerization with electron donor (D) and acceptor (A) units, which can lead to good charge carrier mobilities and narrow energy band gaps [18,19,20,21,22,23,24]. Solution-processed conjugated small molecules have attracted significant attention as candidates for active materials in BHJ solar cells as p-type semiconductor components due to their well-defined molecular structures and molecular weights and their easy purification methods [25,26,27,28,29,30]. Various types of small molecules such as organic dyes, [31,32,33,34,35] oligothiophenes, [36,37,38,39,40] and D-A type molecules have been designed and synthesized to optimize the BHJ solar cell systems [41,42,43,44,45]
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