Abstract
The influence of polymer solution concentration on the performance of chlorobenzene- (CB-) and chloroform- (CF-) based inverted-type organic solar cells has been investigated. The organic photoactive layers consisted of poly(2-methoxy-5-(2-ethyl hexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and (6,6)-phenyl C61butyric acid methyl ester (PCBM) were spin coated from CF with concentrations of 4, 6, and 8 mg/mL and from CB with concentrations of 6, 8, and 10 mg/mL onto Eosin-Y-coated ZnO nanorod arrays (NRAs). Fluorine doped tin oxide (FTO) and silver (Ag) were used as electron collecting electrode and hole collecting electrode, respectively. Experimental results showed that the short circuit current density and power conversion efficiency increased with decrease of solution concentration for both CB and CF devices, which could be attributed to reducing charge recombination in thinner photoactive layer and larger contact area between the rougher photoactive layer and Ag contact. However, the open circuit voltage decreased with decreasing solution concentration due to increase of leakage current from ZnO NRAs to Ag as the ZnO NRAs were not fully covered by the polymer blend. The highest power conversion efficiencies of0.54±0.10% and0.87±0.15% were achieved at the respective lowest solution concentrations of CB and CF.
Highlights
Rapid development in enhancing the performance of organic solar cells (OSCs) for the past few years by utilizing bulk heterojunction (BHJ) devices has enabled power conversion efficiency (PCE) up to 10.6% to be achieved [1]
Different solution concentrations of MEH-PPV and phenyl C61 butyric acid methyl ester (PCBM) were prepared from chlorobenzene (CB) and chloroform (CF). e short circuit current density and power conversion efficiency increased, whereas the open circuit voltage decreased with the reduction of solution concentration. e optimum power conversion efficiencies of 0.54 ± 0.10% and 0.87 ± 0.15% were achieved at the respective lowest solution concentration of CB and CF devices
(∼15 Ω/sq) substrates were ultrasonically cleaned by using acetone and 2-propanol each for 15 min. e ZnO seed layer was spin coated on top of precleaned substrates for 3 times from an equimolar solution (0.2 M) of zinc acetate dehydrate (Zn(O2CCH3)2⋅(H2O)2) and in ethanol followed by annealing diethanolamine (DEA) at 300∘C for one hour in air. e hydrothermal growth of ZnO nanorods arrays (NRAs) was done by immersing ZnO seed coated substrates into an equimolar aqueous solution (40 mM) of zinc nitrate hexahydrate
Summary
Rapid development in enhancing the performance of organic solar cells (OSCs) for the past few years by utilizing bulk heterojunction (BHJ) devices has enabled power conversion efficiency (PCE) up to 10.6% to be achieved [1]. Much effort has been focused on utilizing blend lm of poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl C61 butyric acid methyl ester (PCBM) as photoactive layer in ZnO NRAs-based inverted OSCs [19,20,21,22,23]. Takanezawa et al [25] reported that thicker organic photoactive layer deposited by using higher solution concentration or lower spin coating speed results in better power conversion efficiency as a consequence of improved optical absorption and short circuit current density. E present work reports on the effects of MEH-PPV and PCBM solution concentration on the performance of inverted-type OSCs based on Eosin-Y-coated ZnO NRAs. Eosin-Y organic dye, a low-cost alternative to expensive Rucomplexes dye, has good absorption property and is able to increase the wettability of ZnO surface [28]. Different solution concentrations of MEH-PPV and PCBM were prepared from chlorobenzene (CB) and chloroform (CF). e short circuit current density and power conversion efficiency increased, whereas the open circuit voltage decreased with the reduction of solution concentration. e optimum power conversion efficiencies of 0.54 ± 0.10% and 0.87 ± 0.15% were achieved at the respective lowest solution concentration of CB and CF devices
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