Abstract:A series of P3HT-b-P3PHT diblock copolymers were designed and used as additives to improve the performance of P3HT:PC61BM-based photovoltaic devices.
“…Notably, superior compatibilizing performance is confirmed for the ABA triblock copolymer (PCE increased by 6.6%) when compared to the AB diblock material, due to a change in the crystalline domain orientation from "edge-on" to "isotropic" in the area where PCBM domains are more separated. Improvements in these studies are brought by another block copolymer, P3HT-b-P3PHT [139], which is able to diffuse at the P3HT:PCBM interface and enhance the miscibility between the two blend constituents, inducing an increase in the interfacial area between the P3HT phase and the smaller but more abundant PCBM isles ( Figure 6). Here, the pivotal role has to be attributed to the introduction of the phosphonate group in the hexyl side chains, which provide an amphiphilic nature to the block copolymer, lower melting temperature, and a reduction in the rod-rod interactions, aiming at better dispersion into the blend matrix.…”
Organic Photovoltaics (OPVs) based on Bulk Heterojunction (BHJ) blends are a mature technology. Having started their intensive development two decades ago, their low cost, processability and flexibility rapidly funneled the interest of the scientific community, searching for new solutions to expand solar photovoltaics market and promote sustainable development. However, their robust implementation is hampered by some issues, concerning the choice of the donor/acceptor materials, the device thermal/photo-stability, and, last but not least, their morphology. Indeed, the morphological profile of BHJs has a strong impact over charge generation, collection, and recombination processes; control over nano/microstructural morphology would be desirable, aiming at finely tuning the device performance and overcoming those previously mentioned critical issues. The employ of compatibilizers has emerged as a promising, economically sustainable, and widely applicable approach for the donor/acceptor interface (D/A-I) optimization. Thus, improvements in the global performance of the devices can be achieved without making use of more complex architectures. Even though several materials have been deeply documented and reported as effective compatibilizing agents, scientific reports are quite fragmentary. Here we would like to offer a panoramic overview of the literature on compatibilizers, focusing on the progression documented in the last decade.
“…Notably, superior compatibilizing performance is confirmed for the ABA triblock copolymer (PCE increased by 6.6%) when compared to the AB diblock material, due to a change in the crystalline domain orientation from "edge-on" to "isotropic" in the area where PCBM domains are more separated. Improvements in these studies are brought by another block copolymer, P3HT-b-P3PHT [139], which is able to diffuse at the P3HT:PCBM interface and enhance the miscibility between the two blend constituents, inducing an increase in the interfacial area between the P3HT phase and the smaller but more abundant PCBM isles ( Figure 6). Here, the pivotal role has to be attributed to the introduction of the phosphonate group in the hexyl side chains, which provide an amphiphilic nature to the block copolymer, lower melting temperature, and a reduction in the rod-rod interactions, aiming at better dispersion into the blend matrix.…”
Organic Photovoltaics (OPVs) based on Bulk Heterojunction (BHJ) blends are a mature technology. Having started their intensive development two decades ago, their low cost, processability and flexibility rapidly funneled the interest of the scientific community, searching for new solutions to expand solar photovoltaics market and promote sustainable development. However, their robust implementation is hampered by some issues, concerning the choice of the donor/acceptor materials, the device thermal/photo-stability, and, last but not least, their morphology. Indeed, the morphological profile of BHJs has a strong impact over charge generation, collection, and recombination processes; control over nano/microstructural morphology would be desirable, aiming at finely tuning the device performance and overcoming those previously mentioned critical issues. The employ of compatibilizers has emerged as a promising, economically sustainable, and widely applicable approach for the donor/acceptor interface (D/A-I) optimization. Thus, improvements in the global performance of the devices can be achieved without making use of more complex architectures. Even though several materials have been deeply documented and reported as effective compatibilizing agents, scientific reports are quite fragmentary. Here we would like to offer a panoramic overview of the literature on compatibilizers, focusing on the progression documented in the last decade.
“…It is well known that the electrical and photonic properties of conjugated polymers are not only determined by molecular structure but also strongly affected by processing conditions, during which multiple phase transitions such as collapse transition, phase separation, and crystallization give rise to complex structures and morphologies . Regarding the prototypical organic bulk heterojunction solar cell of P3HT: 1‐(3‐methoxycarbonyl) propyl‐1‐phenyl [6,6] C 61 with similar device configurations, the reported power conversion efficiencies in literature varied over a wide distribution from 0.2 to 6.5%, reflecting extreme dependence of the device performance on microstructural morphologies of the active films . The conjugated polymer‐based device is generally processed from solution via two steps, namely film formation and postannealing .…”
“…For example, in bulk heterojunction (BHJ) solar cells, P3HT is a model compound as the electron donor and a fullerene derivative (e.g., [6,6]‐phenyl‐C 61 ‐butyric acid methyl ester (PCBM)) is as the electron acceptor. The power conversion efficiency (PCE) of the model system (P3HT/PCBM) can be 3–5% with the performance highly related to the P3HT crystallinity and nanoscale morphology of the active layer composed of P3HT/PCBM . Therefore, a lot of work has been done to control the crystalline structure of P3HT.…”
An intriguing morphological transition from poly(3-hexylthiophene) (P3HT) 1D nanofibers to 2D nanoribbons enabled by the addition of a series of alkylthiols is reported. First, P3HT 1D nanofibers are formed due to strong anisotropic π-π stacking between planar rigid backbones. Upon the addition of alkylthiols, P3HT nanofibers are transformed into nanoribbons associated with the crystallographic transition from edge-on orientation to flat-on orientation. The content of alkylthiols has a great influence on the P3HT morphology in the solution. The mechanism of such a morphological transformation is discussed based on the interaction between alkylthiols and P3HT chains. This work offers an effective strategy to tailor the crystal morphology and dimension of P3HT, which not only improves the understanding of P3HT crystallization but also may enable such discovery into conjugated polymer-based optoelectronic devices.
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