Formation of vertical concentration gradients in poly(3-hexylthiophene-2,5-diyl): Phenyl-C61-butyric acid methyl ester-graded bilayer solar cells

Layer-by-layer fabrication of organic photovoltaic devices: material selection and processing conditions

“…22 The P3HT/PC 61 BM system has since been investigated by numerous groups, using a similar methodology to achieve efficiencies comparable or greater than their BHJ counterparts. 24,40,[135][136][137][138][139][140][141][142][143][144][145][146][147][148][149][150][151][152][153][154][156][157][158][159][160][161][162][163][164][165][166][167][168][169][170][171][172] The best reported efficiency of this donor/acceptor system in LbL devices is 5.1%, realized by formation of a bicontinuous donor/acceptor network which resulted in significantly reduced bimolecular recombination. 24 However, these literature reports consistently determined that even without optimization of these processing conditions, interdiffusion between P3HT and PC 61 BM was occurring.…”

“…59 Numerous studies have since shown the pseudo-bilayer morphology is susceptible to variations in the solvent or cosolvent, 130,[144][145][146]157,167,168,170,173,175,177,187,189 but is also influenced by other parameters such as thermal annealing, 24,132,134,137,152,153,155,156,160,161,181,184,191,193,194 use of additives, 26,166,168,171,176,180,182 or addition of binary components to the donor polymer. 141,143,148,158,161 Cho et al explored how solvent choice influenced morphology and phase separation in P3HT layers. Chlorobenzene (CB), DCB, chloroform (CF) and p-xylene (p-XY) were all investigated for processing the P3HT layer, with p-XY also utilized for the PC 61 BM acceptor layer.…”

“…141,161 Film nanostructures can also be controlled through the addition of polyethylene glycol (PEG) or polysterene (PS) in P3HT solutions. 148,158 After extraction of the PS or PEG, the resulting P3HT films contain porous circular depressions whose diameter and depth can be controlled by modification of the polymer ratios during film deposition. Optimization of the PEG content up to 6 wt% increased the PCE from 2.80 to 3.71% for P3HT/PC 61 BM devices.…”

Controlling the concentration gradient in sequentially deposited bilayer organic solar cells via rubbing and annealing

“…9,10 BLs also offer the opportunity to form adequate donor/acceptor vertical concentration gradients in active layers for regular architecture OSCs, which can facilitate charge percolation to the electrodes and reduce leak currents. 11 Unlike BHJ active layers that rely on highly unstable donor/acceptor intermixed networks, the phase separated active layer morphologies of BLs generally leads to longer device lifetimes. 12,13 Furthermore, controlling the BHJ active layer nanomorphology during large-area coating may be difficult and thus the BL strategy is much more attractive for commercial production of OSCs.…”

Transfer-printing of active layers to achieve high quality interfaces in sequentially deposited multilayer inverted polymer solar cells fabricated in air

“…[17–20] In fact, one of the most efficient methods to increase their PCE is to include electron-donor or electron-acceptor only buffer layers between the active layer and the anode or cathode, respectively. Some solution-processed sequential layer deposition processes have been previously introduced and resulted in successfully achieving the adequate morphologies for high efficiency solar cells.…”