Effect of Dual Cathode Buffer Layer on the Charge Carrier Dynamics of rrP3HT:PCBM Based Bulk Heterojunction Solar Cell

• Published in: ACS applied materials & interfaces Vol. 8; no. 17; pp. 10904 - 10910
• Main Authors: Singh, Ashish, Dey, Anamika, Das, Dipjyoti, Iyer, Parameswar Krishnan
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 04.05.2016
• Subjects: aluminum; cathodes; energy; photovoltaic cells; polymers; photovoltaic devices; bulk heterojunction (BHJ) solar cells; charge transport; dual cathode buffer electrode; regioregular poly(3-hexylthiophene)
• ISSN: 1944-8244; 1944-8252; 1944-8252
• DOI: 10.1021/acsami.6b03102

In bulk heterojunction (BHJ) solar cells, the buffer layer plays a vital role in enhancing the power conversion efficiency (PCE) by improving the charge carrier dynamics. A comprehensive understanding of the contacts is especially essential in order to optimize the performance of organic solar cells (OSCs). Although there are several fundamental reports on this subject, a proper correlation of the physical processes with experimental evidence at the photoactive layer and contact materials is essential. In this work, we incorporated three different additional buffer layers, namely, tris­(8-hydroxyquinolinato) aluminum (Alq3), bathophenanthroline (BPhen) or bathocuproine (BCP) with LiF/Al as conventional cathode contact in both rrP3HT:PC61BM and rrP3HT:PC71BM blend BHJ solar cells and their corresponding photovoltaic performances were systematically correlated with their energy level diagram. The device with dual cathode buffer layer having ITO/PEDOT:PSS/blend polymer/BCP/LiF/Al configuration showed the best device performance with PCE, η = 4.96%, J sc = 13.53 mA/cm2, V oc = 0.60 V and FF= 61% for rrP3HT:PC71BM and PCE, η = 4.5% with J sc = 13.3 mA/cm2, V oc = 0.59 V and FF = 59% for rrP3HT:PC61BM. This drastic improvement in PCE in both the device configurations are due to the combined effects of better hole-blocking capacity of BCP and low work function provided by LiF/Al with the blend polymer. These results successfully explain the role of dual cathode buffer layers and their contribution to the PCE improvement and overall device performance with rrP3HT:PCBM based BHJ solar cell.