New D‐A‐A'‐Configured Small Molecule Donors Employing Conjugation to Red‐shift the Absorption for Photovoltaics. Issue 16 (6th July 2020)

• Record Type: Journal Article
• Authors: Wang, Chun‐Kai; Che, Xiaozhou; Lo, Yuan‐Chih; Li, Ya‐Ze; Wang, Yung‐Hao; Forrest, Stephen R.; Liu, Shun‐Wei; Wong, Ken‐Tsung
• Is Part Of: Chemistry, an Asian journal. Volume 15:Issue 16(2020)
• Page Start: 2520
• Page End: 2531
• Publication Date: 2020-07-06
• Subjects: organic photovoltaic -- vacuum process -- small molecule donor -- indoor photovoltaic; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/asia.202000635
• Languages: English
• ISSNs: 1861-4728

Abstract

Abstract: Four new donor‐acceptor‐acceptor' (D‐A‐A')‐configured donors, CPNT, DCPNT, CPNBT, and DCPNBT equipped with naphtho[1, 2 ‐c :5, 6 ‐c′ ]bis([1, 2, 5]‐thiadiazole) (NT) or naphtho[2, 3‐ c ][1, 2, 5]thiadiazole (NBT) as the central acceptor (A) unit bridging triarylamine donor (D) and cyano or dicyanovinylene acceptor (A'), were synthesized and characterized. All molecules exhibit bathochromic absorption shifts as compared to those of the benzothiadiazole (BT)‐based analogues owing to improved electron‐withdrawing and quinoidal character of NT and NBT cores that lead to stronger intramolecular charge transfer. Favorable energy level alignments with C70, together with the good thermal stability and the antiparallel dimeric packing render CPNT and DCPNT suitable donors for vacuum‐processed organic photovoltaics (OPV)s. OPVs based on DCPNT : C70 active layers displayed the best power conversion efficiency (PCE)=8.3%, along with an open circuit voltage of 0.92 V, a short circuit current of 14.5 mA cm −2 and a fill factor of 62% under 1 sun intensity, simulated AM1.5G illumination. Importantly, continuous light‐soaking with AM 1.5G illumination has verified the durability of the devices based on CPNT :C70 and DCPNT : C70 as the active blends. The devices were examined for their feasibility of indoor light harvesting under 500 lux illumination by a TLD‐840 fluorescent lamp, giving PCE =12.8% and 12.6%, respectively. These results indicate that the NT‐based D‐A‐A'‐type donors CPNT and DCPNT are potential candidates for high‐stability vacuum‐processed OPVs suitable for indoor energy harvesting. Abstract : New donor‐acceptor‐acceptor' (D‐A‐A')‐configured small molecule donors with extended π‐conjugation for red‐shifting the absorption were characterized. The OPV comprising the donor DCPNT bearing naphtho[1, 2 ‐c :5, 6 ‐c′ ]bis([1, 2, 5]‐thiadiazole) (NT) as A, cyano as A', and acceptor C70 displayed the power conversion efficiency of 8.3% under AM 1.5G and 12.8% under 500 lux of TLD‐840 lamp, indicating the potential for indoor photovoltaics application.