Copper Bromide as an Efficient Solution-Processable Hole TransportLayer for Organic Solar Cells: Effect of Solvents

摘要

In this work, we report copper bromide (CuBr) as an efficient, inexpensive, and solution-processable hole transport layer (HTL) for organic solar cells (OSCs) for the first time. To examine the effectiveness of the material in general, three different solvents such as acetonitrile (MeCN), dimethyl sulfoxide (DMSO), and dimethylformamide (DMF) are used for solution-processing thin-film deposition of CuBr. CuBr thin films deposited from different solvents show high transparency and no significant difference has been observed in absorption in the visible and near-IR range, whereas a slight difference has been found in the near-UV range by changing the solvents. Furthermore, two most studied combinations of the active layer such as PTB7/PC71BM and PCDTBT:/PC71BM are used for device fabrication with geometry of ITO/CuBr(HTL) active layer/Al. By using CuBr as a HTL in OSCs, the power conversion efficiencies (PCEs) have been achieved to up to 5.16 and 4.72% with PTB7/PC71BM and PCDTBT/PC71BM active layers, respectively. The CuBr film from DMF solvent shows highest PCE as compared to films deposited from DMSO and MeCN solvents.Different solvents used for HTL deposition have a major effect onthe fill factor (FF), while very little difference on open circuitvoltage (Voc) and short circuit current(Jsc) has been observed. It may be mentionedhere that a small difference of device parameters (PCE, FF, Jsc, and Voc) hasbeen observed in the devices using the HTL deposited from DMF andDMSO solvents, whereas a significant difference of the device parametershas been found in devices using the HTL from MeCN solvent.