Three novel pyrido [2,3,4,5-lmn]phenanthridine derivatives of 4, 9-dialkylpyrido[2,3,4,5-lmn]phenanthridine-5,10-dione, 10-alkoxy-4-alkylpyrido[2,3,4,5-lmn]phenanthridin-5-one, and 5,10-dialkoxypyrido[2,3,4,5lmn]phenanthridine were synthesized as building blocks of copolymers Pa, Pb and Pc, giving relatively large band gaps of 2.13, 2.19 and 2.21 eV, respectively. Bulk-heterojunction (BHJ) solar cells were fabricated in a typical device configuration by utilizing the resulting polymers as the donor of the active layer. A power conversion efficiency (PCE) of 3.47% was achieved from the Pa-based device without any additives or thermal annealing. A further improved PCE of 4.54% was achieved in inverted device architecture, and it is hitherto the highest efficiency of BHJ polymer solar cells using a donor polymer with a band gap above 2.1 eV.

Biodiesel is a high‐quality diesel alternative fuel, but it can get easily oxidized on long‐term storage. The addition of antioxidants can effectively improve the oxidation stability of biodiesel. In this study, the mechanism of phenolic antioxidants to inhibit the oxidation of biodiesel and reduce the NOX emission is discussed based on the experimental investigation. Antioxidants (0.8 wt%) 3‐tert‐butyl‐4‐methoxyphenol (BHA), rosemary (K1), and tea polyphenols (K2) were added to biodiesel B100. The antioxidant test was carried out at atmospheric temperature for 4320 h, and the peroxide value, acid values were measured. Then, 0.8 wt% of K1, K2, and BHA were added to B20, named as K1B20, K2B20, and BHAB20. The 186F diesel engine bench test was carried out under 10%, 25%, 50%, 75%, and 100% load at 3000 rpm, with HC, CO, NOX, and smoke emissions of various types of fuel (B20, BHAB20, K1B20, and K2B20) were measured. The results of antioxidant test showed that the antioxidant effect of rosemary was best, displaying a decrease in acid and peroxide values by 25% and 48%, respectively. The diesel engine bench test results showed that antioxidants had little effect on HC, CO, and smoke emission; however, the antioxidants significantly reduced NOX emission. The effect of natural antioxidant rosemary to reduce NOX emission is the best one. At 3000 rpm and 75% load, the NOx of B20 reduced by 9.4%. Among the three antioxidants, the experimental results verified the mechanistic analysis and provided the basis for the selection of antioxidants for biodiesel. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019