Proceedings Article | 18 September 2018
KEYWORDS: Annealing, Molecules, Organic photovoltaics, Solar cells, Atomic force microscopy, Heterojunctions, Fermium, Frequency modulation, Bismuth, Tin
Here is presented the impact of thermal (TA) and solvent vapor annealing (SVA) post-treatments in bulk heterojunction (BHJ)-film formation of OSCs based on DRCN5T small molecule (based on oligothiophenes [1]) as electron donor and [70]PCBM as electron acceptor, under the direct architecture ITO/PEDOT:PSS/DRCN5T:[70]PCBM/PFN/FM, where FM is an eutectic alloy composed of 32.5% Bi, 51% In and 16.5% Sn, that melt at 65 °C and is easily deposited as top electrode at low temperature (~ 90 °C) [2-4]. The evolution of thin active layer formation treated by TA (120 ºC/10 min), SVA (in chloroform/60 s) and the combination TA+SVA was studied by atomic force microscopy (AFM) in phase contrast mode in order to determine the size domains for each post-treatment (TA, SVA or TA+SVA). The results show domains up to 500 nm wide for active layers without further post-treatment and the PCE achieved for devices fabricated with these active layers was 2.15%. On the other hand, both TA and SVA post-treatments show domains in the range of 100 to 150 nm wide as maximum, which is favorable for an efficient transport of electronic species. The PCEs for the devices were 4.96 and 4.91% for active layers treated with TA and SVA, respectively. Finally, devices with active layers treated by the combination of TA+SVA reached PCEs of 7.63 %.
References
[1] B. Kan et al, J. Am. Chem. Soc. 2015, 137, 3886-3893.
[2] E. Pérez-Gutiérrez, et al., ACS Appl. Mater. Interfaces 2016, 8, 28763.
[3] D. Romero-Borja, et al., Synth. Met. 2015, 200, 91-98.
[4] D. Barreiro-Argüelles et al., Solar Energy, accepted (2018).
Acknowledgements: Ce-MIE-Sol 207450/27, CONACyT-SENER 24575 and CONACyT 281164 (LNMG) Mexico.
