Thermally Stable Bulk Heterojunction Prepared by Sequential Deposition of Nanostructured Polymer and Fullerene

Abstract

Abstract:A morphologically-stable polymer/fullerene heterojunction has been prepared by minimizing the intermixing between polymer and fullerene via sequential deposition (SqD) of a polymer and a fullerene solution. A low crystalline conjugated polymer of PCPDTBT (poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b ]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]) has been utilized for the polymer layer and PC 71 BM (phenyl-C 71 -butyric-acid-methyl ester) for the fullerene layer, respectively. Firstly, a nanostructured PCPDTBT bottom layer was developed by utilizing various additives to increase the surface area of the polymer film. The PC 71 BM solution was prepared by dissolving it in the 1,2-dichloroethane (DCE), exhibiting a lower vapor pressure and slower diffusion into the polymer layer. The deposition of the PC 71 BM solution on the nanostructured PCPDTBT layer forms an inter-digitated bulk heterojunction (ID-BHJ) with minimized intermixing. The organic photovoltaic (OPV) device utilizing the ID-BHJ photoactive layer exhibits a highly reproducible solar cell performance. In spite of restricted intermixing between the PC 71 BM and the PCPDTBT, the efficiency of ID-BHJ OPVs (3.36%) is comparable to that of OPVs (3.87%) prepared by the conventional method (deposition of a blended solution of polymer:fullerene). The thermal stability of the ID-BHJ is superior to the bulk heterojunction (BHJ) prepared by the conventional method. The ID-BHJ OPV maintains 70% of its initial efficiency after thermal stress application for twelve days at 80 • C, whereas the conventional BHJ OPV maintains only 40% of its initial efficiency.

Efficient non-fullerene organic solar cells employing sequentially deposited donor–acceptor layers

“…This structure, termed a sequentially deposited BHJ (sq-BHJ), has been used in fullerene-based OSCs, sometimes yielding quantum efficiencies comparable to an as-cast BHJ (c-BHJ) based on D:A co-deposition. 17,18,[27][28][29][30][19][20][21][22][23][24][25][26] For example, the state-of-the-art sq- With fullerene-based semiconductors remaining the archetypal electron acceptor for OSCs, the recent fast advancement of high-performance non-fullerene acceptors (NFAs) has motivated a careful evaluation of the future direction of OSC research. [31][32][33][34][35] Beginning in 2015, the PCEs of champion NFA-based single-junction OSCs have been higher than those fabricated using fullerenes, and now stands at an impressive 14%.…”

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

“…1, a8-9) fullerene small molecules, paired with lower band gap conjugated polymers, permitting increased efficiencies up to almost 9%. 23,25,26,30,155,[173][174][175][176][177][178][179][180][181][182][183][184][185][186] Recently, NFAs have been integrated into spin casted bilayer devices, enabling PCEs in excess of 10%. 28,29,44,49,59,123,125,126,129,130,133,[187][188][189][190] One example of a NFA system is PBTB-TFS1 ( Fig.…”

“…59 Cui et al demonstrated that solubility and solvent choice are key for high performing LbL OPV devices. 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.…”

Investigations of Novel High-Temperature Resistant Polymers for Electro-Optical Applications in Signal Processing Systems

“…The whole set of spectroscopic characteristics (both steady-state and time-resolved) will be performed to select the most promising constituents for host-guest systems. Second-order nonlinear susceptibility of poled metal-polymers, organo-polysilanes and their composites will be measured by SHG and electro-optical techniques [15]. Quantum-chemical calculations will be performed to estimate the first hyperpolarizability of the polymer's sub-units.…”