Owing to their high designability over properties, solution-processibility and flexibility, conjugated polymers have been regarded as a class of promising materials for new generation optoelectronics. Herein, we present an efficient molecular engineering approach on conjugated side chains for highly sensitive polymer photodetector and high performance solar cells. First, 3,4-ethylenedioxythiophene (EDOT) is introduced as conjugated side chain to functionalize the backbone of the semiconducting polymers. The EDOT functionalization has little effect on the photovoltaic performance, but significantly depresses the dark current density of the photodetector at reverse bias when comparing to thiophene counterparts. These EDOT polymer based photodetectors exhibit high rectification ratio of over 6 order for dark current density at ±2.0 V and good photodetectivity of around 1013 Jones, and are able to detect weak light linearly down to sub pW/cm2. It is found that the EDOT unit increases the interaction between the polymer and PEDOT layer, forming polymer rich layer near the PEDOT surface, which could account for the dark current reduction at reverse bias. To improve the photovoltaic performance of benzo[1,2-b:4,5-b']dithiophene (BDT) based polymers, 4-methoxy group modified thiophene (MOT) is employed as the conjugated side chain. Deeper HOMO levels and stronger interchain interactions are observed for BDT-MOT polymers compared with thiophene control polymers. Therefore, the corresponding PSCs exhibit enhanced open-circuit voltage and improved power conversion efficiency (PCE) compared to the thiophene counterparts. Over 11% PCE has been demonstrated in our polymer solar cell systems.

Molecular engineering on conjugated side chains for high performance polymer photodetectors and solar cells

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.