Solvent-Resistant Organic Transistors and Thermally Stable Organic Photovoltaics Based on Cross-linkable Conjugated Polymers

Abstract

Conjugated polymers, in general, are unstable when exposed to air, solvent, or thermal treatment, and these challenges limit their practical applications. Therefore, it is of great importance to develop new materials or methodologies that can enable organic electronics with air stability, solvent resistance, and thermal stability. Herein, we have developed a simple but powerful approach to achieve solvent-resistant and thermally stable organic electronic devices with a remarkably improved air stability, by introducing an azide cross-linkable group into a conjugated polymer. To demonstrate this concept, we have synthesized polythiophene with azide groups attached to end of the alkyl chain (P3HT-azide). Photo-cross-linking of P3HT-azide copolymers dramatically improves the solvent resistance of the active layer without disrupting the molecular ordering and charge transport. This is the first demonstration of solvent-resistant organic transistors. Furthermore, the bulk-heterojunction organic photovoltaics (BHJ OPVs) containing P3HTazide copolymers show an average efficiency higher than 3.3% after 40 h annealing at an elevated temperature of 150 °C, which represents one of the most thermally stable OPV devices reported to date. This enhanced stability is due to an in situ compatibilizer that forms at the P3HT/PCBM interface and suppresses macrophase separation. Our approach paves a way toward organic electronics with robust and stable operations.

Benzocyclobutene-fullerene bisadducts as novel electron acceptors for enhancing open-circuit voltage in polymer solar cells

“…In addition, the (010) reflection peaks from the π-π stacking of P3HTs in two different active layers appeared in both in-plane (edge-on) and out-of-plane (face-on) directions, which is commonly observed in previous works [45,46]. The π-π stacking distance (010) of P3HT in both BCBCBA and bis-PCBM mixed film was calculated to be 0.38 nm (q z ¼1.65 Å À 1 ) from the out-of-plane plot, consistent with the literature values for well-ordered P3HT crystals [47][48][49]. For quantitative analysis of the crystalline order of P3HT, the crystal size of P3HT in each active layer was calculated using Scherrer equation [48,[50][51][52][53].…”

Morphological study of polymer/fullerene interfaces via benzene–PCBM interaction

“…The parent copolymer and all random copolymers exhibited high thermal stabilities (see Table 1) with decomposition temperatures (5% weight loss = T d ) ranging from 320 to 475°C (RP1, T d = 383°C; RP2, T d = 374°C; and RP3, T d = 344°C; and P1, T d = 355°C). Thus, the synthesized random copolymers are potential candidates for fabricating optoelectronic devices [33,34]. Furthermore, the DSC measurements obtained from the copolymers revealed that P1 and RP1-RP3 were amorphous and did not display noticeable glass transition temperatures (i.e., no melting and no recrystallization points) over the temperature range 30-400°C under a nitrogen atmosphere (see Fig.…”

Novel Approaches in the Design of Donor-Acceptor Oligomeric and Polymeric Materials for Photovoltaic Applications: D/A Blend versus Self-assembly of D/A by Covalent or Non-Covalent Interaction

“…The photovoltaic performance of single component solar cell of D-A copolymer once again showed higher PCE of 2.46% compared to the random copolymer [110]. Most of the reports on D-A block copolymers employ them as compatibilizer rather than as the active layer component of solar cell, where they are used in small amounts along with P3HT: PC 61 BM blend [111][112][113]. Although covalent linkage of the fullerene with donor polymer blocks did not yield high device efficiencies compared to the blend, latest research in this area highlighted the vital role of the D-A block copolymers in improving the thermal stability of P3HT: PC 61 BM blend solar cell devices by reducing interfacial energy between donor (P3HT) and acceptor (PC 61 BM) which ultimately reduced their phase separation.…”