Browsing by Author "Hsieh, Zong-Chun"

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Plasmonic Effects on Bulk Heterojunction Polymer Solar Cells: A Transient Photovoltage and Differential Charging Study
(2017-08-01)
Kok, Soon Yie
;
Hsieh, Zong-Chun
;
Chou, Chun-Hsien
;
Yang, Shun-Shing
;
Chuang, Ming-Kai
Transient photovoltage and differential charging experiments have been carried out to investigate the plasmonic effects in organic photovoltaic devices (OPVs). We observed that the carrier lifetimes became longer after the Au nanoparticles were blended into the OPVs. Additionally, the charge carrier densities also became higher in the bulk of the device. The carrier lifetime, however, usually follows an inverse power relationship with the increasing charge density in OPVs fabricated base on the concept of bulk heterojunctions. Therefore, we conclude that one of the limitations for the plasmonic approaches could be the strong bimolecular recombination.
Toward High-Performance Polymer Photovoltaic Devices for Low-Power Indoor Applications
(2017-12-01)
Yang, Shun-Shing
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Hsieh, Zong-Chun
;
Keshtov, Muchamed L.
;
Sharma, Ganesh D.
;
Chen, Fang-Chung
This article describes the performance of organic photovoltaic (OPV) devices, incorporating three different polymer/fullerene derivative blends, under low-level lighting conditions. The devices exhibit much higher power conversion efficiencies (PCEs) under indoor lighting conditions than they do under sunlight. The best-performing device is capable of delivering a power output of 22.57Wcm(-2), corresponding to a PCE of 13.76%, under illumination with indoor lighting conditions at 500 lux. Increasing the open-circuit voltage (V-oc) of the OPV devices is the most critical factor for achieving high device performance for low-power indoor applications. Therefore, the device power output will be maximized if we could obtain a larger energy difference between the highest occupied molecular orbital of the polymer donor and the lowest unoccupied molecular orbital of the electron acceptor, thereby ensuring a high value of V-oc.