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We have designed and synthesized two wide bandgap new donor‐acceptor (D‐A) copolymers consisting of the same alkylthiazole‐substituted benzo[1,2‐b;4,5‐b′]dithiophene (BDTTz) donor unit and but different acceptor units, i.e., thiazolo[5,4‐d]thiazole (TTZ) (P122) and 1,3,‐4 thiadiazole (TDz) (P123) and investigated their optical and electrochemical properties. We have employed these copolymers as donor and fullerene (PC71BM) and narrow bandgap non‐fullerene (Y6) as acceptor, to fabricate binary and ternary bulk heterojunction polymer solar cells (PSCs). The overall power conversion efficiency (PCE) of optimized binary bulk heterojunction PSCs based on P122:Y6 and P123:Y6 is 12.60% and 13.16%, respectively. The higher PCE for PSCs based on P123than P122counterparts may be associated with the broader absorption profile of the P123and more charge carrier mobilities than that for the P122active layer. With the incorporation of small amount of PC71BM into either P122:Y6 or P123:Y6 binary blend, the corresponding ternary PSCs showed an overall PCE of 14.89% and 15.52%, respectively, which is higher than the binary counterparts using either Y6 or PC71BM as acceptor. Incorporating the PC71BM in the binary host blend increases the absorption in the 300–500 nm wavelength region, generating more excitons in the active ternary layer and helping to dissociate the excitons into free charge carriers more effectively. The more appropriate nanoscale phase separation in the active ternary layer than the binary counterpart may be one of the reasons for higher PCE.

Herein we report the synthesis of a novel A-D-A-D-A non-fullerene small-molecule acceptor (NFSMA) bearing a diketopyrrolopyrrole (DPP) acceptor central core coupled to terminal rhodanine acceptors via a thiophene donor linker (denoted as MPU1) for use in non-fullerene polymer solar cells (PSCs). This NFSMA exhibits a narrow optical band gap (1.48 eV), strong absorption in the 600–800 nm wavelength region of the solar spectrum, and a lowest unoccupied energy level of −3.99 eV. When the mixture of a medium band gap D–A copolymer P (1.75 eV) was used as donor and MPU1 as acceptor, the blend film showed a broad absorption profile from 400 to 850 nm, beneficial for light harvesting efficiency of the resulted polymer solar cell. After optimization of the donor-to-acceptor weight ratios and concentration of solvent additive, the P–MPU1-based PSC exhibited a power conversion efficiency of 7.52% (Jsc= 12.37 mA/cm2, Voc= 0.98 V, and fill factor = 0.62), which is much higher than that for a P3HT–MPU1-based device (2.16%) prepared under identical conditions. The higher value for the P–MPU1-based device relative to the P3HT–MPU1-based one is related to the low energy loss and more balanced charge transport in the device based on the P donor. These results indicate that alteration of the absorption spectra and electrochemical energy levels of non-fullerene acceptors, and appropriate selection of the polymer donor with complementary absorption profile, is a promising means to further boost the performance of PSCs.

Two donor–acceptor (D–A) backbone copolymers with different fused ring acceptors, i.e., dithieno [2,3‐e:3′,2′‐g]isoindole‐7,9(8 H)‐dione (DTID) and dithieno[3′,2′:5,6;2″,3″:7,8]naphtho[2,3‐d]imidazol‐9(10 H)‐one (DTNID) and same benzo[1,2‐b:4,5‐b′]dithiophene with alkylated aromatic side as side chains (BDTT) donor, denoted as P133and P135are synthesized and used as donor along with narrow bandgap nonfullerene Y6 acceptor for the preparation of polymer solar cells (PSCs). The dielectric constant of P135:Y6 is higher than that of P133:Y6 due to the strong electron deficient ability of DTNID compared to DTID, which fostered exciton dissociation and charge transport, constrained charge recombination, and ultimately boosted the power conversion efficiency of P135:Y6 to 15.11%, which is higher than P133:Y6 (10.24%). Therefore, these investigations confirm the pronounced potential of fused ring DTNID as an acceptor unit for emerging D–A copolymers for PSCs with high efficiency. The power conversion efficiency for P135:Y6 (15.11%) is higher than that for P133:Y6 (10.24%), which is attributed to the efficient charge separation and transport due to the high dielectric constant of the former blend, owing to the reduced exciton binding energy due to the two polar carbonyl groups in P135 donor–acceptor copolymer.

Two novel regular terpolymers that are of D-A1–D-A2 type and contain benzothiadiazole and 2,5-dibromo-8-dodecanoylbenzo[1,2-b:3,4-b′:5,6-d″]trithiophene (P1) or 2,8-dibromo-5-dodecanoylbenzene[1,2-b:3,4-b′:5,6-d″]trithiophene (P2) acceptor units with the same thiophene donor were synthesized through Stille coupling, and their optical and electrochemical properties were investigated. The highest occupied molecular orbital (HOMO) and lowest unoccupied (LUMO) molecular orbital energy levels of these terpolymers indicate that there is sufficient LUMO offset with PCBM for efficient exciton dissociation, and their deeper HOMO levels ensure the high open-circuit voltage for the resultant bulk heterojunction solar cells. Measurements on the solar cell devices also confirm that compared to those based on P2the devices based on P1possess a higher short-circuit photocurrent (Jsc) as well as a higher fill factor (FF), which is attributed to the lower bandgap and higher hole mobility for P1, whereas the Vocis higher for the devices that are based on P2, which may be a result of P2 having a lower HOMO energy level than P1. The optimized polymer solar cells fabricated using P1:PC71BM (DIO/CF) and P2:PC71BM (CF/DIO) for the active layers showed a PCE of 7.19% and 6.34%, respectively. Atomic force microscopy (AFM) images of P1:PC71BM blend films show that they exhibit more suitable morphology with favorable interpenetrating networks, which favors high Jscand FF. Moreover, P1exhibits a more crystalline nature than P2that also favors the charge transport. This may be a result of better molecular packing, more distinct phase separation of the blended films, as well as a reduction of charge recombination.

Hybrid organic/inorganic perovskites are promising candidate materials for use in photovoltaic applications. More recently, they have also become highly attractive as active materials for other optoelectronic devices, including lasers, light-emitting diodes, and photodetectors. Nevertheless, difficulties in forming continuous and uniform films and the existence of a charge-injection barrier between the perovskite layer and the electrodes have hindered the development of high-performance perovskite light-emitting diodes (PeLEDs). In this study, a cross-linked hole-transport layer (HTL) is introduced to improve the hole-injection efficiency of PeLEDs. Furthermore, this layer simultaneously facilitates the formation of smooth perovskite layers, presumably because of the different surface energies. More interestingly, the HTL also exhibits strong solvent effects on the device performance. When the processing solvent for fabricating the HTLs is changed from chlorobenzene to N,N-dimethylformamide (DMF), the perovskite layer becomes more uniform and continuous, leading to better surface coverage and higher device efficiency, presumably because DMF has strong affinity toward the perovskite precursors. The approach presented herein could become a general method for decreasing the hole-injection barrier of PeLEDs and, eventually, lead to higher device performance.

The series of new bis(naphthalic anhydrides) was prepared through Diels‐Alder cycloaddition. The Diels‐Alder cycloaddition was used as a synthetic route to new phenylated monomers as well as to polymers. All polymers synthesized revealed to be soluble in a wide range of organic solvents such as toluene, THF, chloroform, and displayed high thermostability. Therefore, they can be processed easily and are promising candidates for advanced coating systems as well as for electrooptical applications.

Herein, ternary active layer‐based polymer solar cells using two donor (D)–acceptor (A) conjugated polymers P1 and P3 having same A unit and different D units as donor along with the nonfullerene small molecule acceptor, BThIND‐Cl, are fabricated. The polymer solar cells based on P1:BThIND‐Cl and P3:BThIND‐Cl binary show power conversion efficiency of 12.13% and 13.08% with energy loss of 0.60 and 0.51 eV, respectively. The open circuit voltage of the P3 based polymer solar cells is higher than that for P1 counterpart associated with the deeper highest occupied molecular orbital (HOMO) energy level of P3 as compared to the P1. The small energy loss for P3 may be attributed to low HOMO offset between P3 and BThIND‐Cl. Moreover, the short circuit current density is higher for the P1 based polymer solar cell. Taking the advantages of high valve of short circuit current for P1 and larger value of open circuit voltage for P3 counterpart, optimized polymer solar cells using these two polymers and BThIND‐Cl as acceptor and after the optimization, the polymer solar cells based on P1:P3:BThIND‐Cl showed overall power conversion efficiency of 15.78% with energy loss of 0.55 eV. Ternary polymer solar cells using two polymers P1 and P3 with similar chemical structures and a nonfullerene acceptor are fabricated. The attained power conversion efficiency is over 15.5% with low energy loss of 0.55 eV, which is larger than that for binary counterparts processed under identical conditions.