Charge-Transfer State Energy and Its Relationship with Open-Circuit Voltage in an Organic Photovoltaic Device

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• 作者：Zhiqiang Guan ; Ho-Wa Li ; Yuanhang Cheng ; Qingdan Yang ; Ming-Fai Lo ; Tsz-Wai Ng ; Sai-Wing Tsang ; Chun-Sing Lee
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：July 7, 2016
• 年：2016
• 卷：120
• 期：26
• 页码：14059-14068
• 全文大小：592K
• 年卷期：0
• ISSN：1932-7455

文摘

Charge-transfer state (CTS) plays a very important role in organic photovoltaic (OPV) devices. Especially the relationship between open-circuit voltage (V_OC) and CTS has been widely discussed. It is proposed that the CTS energy (E_CT) directly determines the V_OC value; however, the E_CTs measured from different techniques often show considerable discrepancy. Here four methods are applied to probe the E_CT values in five different bulk-heterojunction polymer:fullerene OPVs. It is found that linear relationships exist between different E_CT’s and V_OC values. The detailed energetic meanings of the E_CT values measured from different techniques are discussed, and the origin of their discrepancy is analyzed. Lastly, based on a proposed energy model, a relationship is summarized to estimate V_OC loss by considering the energetic broadening of CTS, bimolecular recombination, and dielectric effect. The results provide a guideline to forecast the V_OC and investigate its loss in OPV.