A simple method to adjust the morphology of gradient three-dimensional PTB7-Th:PC₇₁BM polymer solar cells

Abstract

Multiple interfaces are necessary for exciton separation in bulk heterojunction (BHJ) solar cells and continuous pathways for carrier transportation in donor : acceptor blend films, especially along the vertical direction, for efficient charge collection. Therefore film morphology is critically important to satisfy both in the construction of high performance organic solar cells (OSCs). In this work, the cooperative effect of solvent additives and solvent flux treatment on film morphology was confirmed. Furthermore, the correlation between a single processing parameter and the resulting morphology has been investigated. Our results show that film morphology can be tuned by changing the volume fraction of the solvent additive. Beyond that, after methanol fluxing, the OSC performance improves significantly, as short circuit current density (JSC) increases from 13.85 mA cm(-2) to 15.17 mA cm(-2) and fill factor (FF) from 62.9% to 65.7%, simultaneously. As a result, power conversion efficiency (PCE) increases from 6.79% to 7.67%. The favorable morphology was further investigated using time-of-flight secondary-ion mass spectroscopy (TOF-SIMS), and atomic force microscopy (AFM).

Restricting the liquid–liquid phase separation of PTB7-Th:PF12TBT:PC71BM by enhanced PTB7-Th solution aggregation to optimize the interpenetrating network

“…The performance of PTB7-Th:PC 71 BM devices is largely determined by the nanoscopic and mesoscopic active layer morphology according to extensive studies. [31][32][33][34] When PF12TBT was introduced, more variables were brought in. Thus, the ternary solar cells need to be carefully investigated to achieve a successful case.…”

Design, fabrication and charge recombination analysis of an interdigitated heterojunction nanomorphology in P3HT/PC70BM solar cells

“…10,11,[13][14][15][16][17] It is well known that power conversion efficiency is limited, among other factors by the diffusion length of excitons in the photoactive layer after they have been generated (typically this length is in the range of tens of nanometers in most organic semiconductors). 19,24,25 The main progress in IHJN has been achieved by new fabrication techniques and technologies. The free electrons and holes after the exciton dissociation, they are transported by their corresponding material and collected at the metal electrodes.…”

Tuning crystalline ordering by annealing and additives to study its effect on exciton diffusion in a polyalkylthiophene copolymer

“…S6d-g, ESI †). This may be due to trapped traces of DIO 43,44 (even though the samples were kept at 10 À5 mbar vacuum for 4-5 hours). Interestingly, when such films were thermally or melt annealed their roughness got significantly reduced (Fig.…”