Dual-functional cathode buffer layer for power conversion efficiency enhancement of bulk-heterojunction solar cells
SYNTHETIC METALS
Authors: Datt, Ram; Bishnoi, Swati; Gupta, Ramashanker; Haranath, D.; Sharma, Shailesh N.; Gupta, Govind; Arya, Sandeep; Kumar, S.; Gupta, Vinay
Abstract
Here, we report a luminescent cathode buffer layer (CBL) for power conversion efficiency (PCE) enhancement of organic solar cells (OSCs). ZnO doped with Aluminum (Al) and Europium (Eu) was cast as CBL by a solution-processed method. CBL serves a dual purpose by acting both as a spectral conversion and an electron transporting layer. The luminescent ZnO:Al,Eu CBL layer has broad absorption spanning the ultraviolet (300-400 nm) spectrum, contributing to absorption enhancement. Moreover, the emission of CBL layer overlaps with the absorption of poly [N -9'-heptadecanyl-2,7-carbazole- alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) polymer thus elevating the overall absorption of the active layer and improving the photocurrent With this ZnO:Al,Eu CBL in the inverted device configuration (ITO/CBL/active layer/MoOx/Al), an enhanced power conversion efficiency (PCE) of 6.9% was obtained while the device with pristine ZnO as CBL showed PCE of 5.9%. A blend of PCDTBT donor and [6,6]-phenyl C-71 butyric acid methyl ester (PC71BM) acceptor was used as an active layer in both the cases. In ZnO:Al,Eu CBL layer, Al doping improves the conductivity, while Eu doping significantly enhances the emission in the visible region by down-shifting the incoming solar UV light to the visible range which overlaps with the absorption of PCDTBT polymer resulting in energy transfer and improved overall device efficiency. The findings of the study show the significance of luminescent znO:ALEu nanoparticle CBL in enhancing the performance of organic solar cells.
Development of Case-Based Learning (CBL) in Engineering Technology Education
INTERNATIONAL JOURNAL OF ENGINEERING EDUCATION
Authors: Alani, Faiez
Abstract
Case-based learning (CBL) is an active learning technique that has traditionally been underutilized in engineering technology education research. Real-life case studies were developed and used in teaching and learning two biotechnology courses in winter 2019. The overall student evaluation of CBL was positive: 71% of students agreed that CBL enhanced their learning, while 13% disagreed and 16% of students were neutral. 74% of students found that CBL helped them in team working skill and 24% were neutral. Detailed evaluation and discussion of CBL enhancement on problem solving, critical thinking, learning experience and technical skills are carried out in this study.