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Correlating nanoscale morphology with device performance in conventional and inverted PffBT4T-2OD:PC71BM polymer solar cells

DOI: 10.1021/acsaem.8b00727 DOI Help

Authors: Yu Yan (Wuhan University of Technology) , Wei Li (Wuhan University of Technology) , Feilong Cai (Wuhan University of Technology) , Jinlong Cai (Wuhan University of Technology) , Zhiwei Huang (Wuhan University of Technology) , Robert S. Gurney (Wuhan University of Technology) , Dan Liu (Wuhan University of Technology) , David G. Lidzey (University of Sheffield) , Andrew J. Pearson (University of Cambridge) , Tao Wang (Wuhan University of Technology)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Applied Energy Materials

State: Published (Approved)
Published: June 2018
Diamond Proposal Number(s): 17223

Abstract: Nanoscale morphology has been established as one of the controlling factors in the device performance of bulk heterojunction polymer solar cells. We report in this work morphology changes in both lateral and vertical directions in PffBT4T-2OD:PC71BM solar cells, as well as their effects on device performance. Thermal annealing was found to increase the crystallinity of PffBT4T-2OD and domain size of PC71BM clusters without any observable impact on vertical component redistribution, whilst methanol rinsing reduces the crystallinity of PffBT4T-2OD, encourages the migration of PC71BM towards the mixed polymer-rich phase as well as towards the film surface on both PEDOT:PSS and TiO2 substrates. The polymer-rich surface region in vacuum- and thermal annealing- treated conventional devices obstructs electron injection towards the cathode, and reduces the maximum achievable device efficiency, whilst this polymer-rich surface region is beneficial in the inverted devices. However, although a PC71BM-rich region will locate at the cathode or anode interface upon methanol rinsing treatment in conventional and inverted devices respectively, holes can still be effectively injected from both sides the device to ensure effective charge transport, as supported by a number of optoelectronic property investigations.

Journal Keywords: Polymer solar cell; organic photovoltaics; nanoscale morphology; vertical component distribution; device efficiency; PffBT4T-2OD

Subject Areas: Materials, Chemistry, Energy


Instruments: I07-Surface & interface diffraction

Other Facilities: Shanghai Synchrotron Radiation Facility