Highly Efficient Non‐Fullerene Polymer Solar Cells Enabled by Wide Bandgap Copolymers With Conjugated Selenyl Side Chains

Abstract

In this work, the authors design and synthesize two novel wide bandgap copolymers based on selenophene substituted benzo[1,2‐b:4,5‐b']dithiophene (BDTSe) as the donor unit and fluorinated benzotriazole as the acceptor unit for high performance non‐fullerene polymer solar cells (NF‐PSCs). A larger maximum molar extinction coefficient (ϵ) of 8.54 × 104 M−1 cm−1 is achieved when introducing sulfur atom onto the two‐dimensional (2D) BDTSe units, which should realize the better complementary absorption with ITIC as the acceptor, leading to a higher Jsc of 19.51 mA cm−2. Furthermore, a lower highest occupied molecular orbital (HOMO) energy level with almost no change in bandgap can be also achieved after inserting the sulfur atoms, thus resulting in an enhanced open‐circuit voltage (Voc) of 0.84 V without sacrificing the short‐current density (Jsc). In addition, the higher crystallinity and optimized morphology are found to be beneficial to more efficient exciton dissociation and charge transport, giving rise to a higher fill factor (FF) of 75.1% and an elevated power conversion efficiency (PCE) of 12.31%. The results indicate that the strategy of alkylthioselenyl side chains on the BDT unit for constructing the donor‐acceptor (D‐A) copolymer donor materials is an excellent approach for realizing highly efficient NF‐PSCs.

Wide bandgap polymer donors for high efficiency non-fullerene acceptor based organic solar cells

“…7d) 18 were replaced with selenophene side chains, the obtained PN10 (PBDT-Se-TAZ) exhibited similar E HOMO (-5.23 vs. -5.26 eV) and E g (1.92 vs. 1.91 eV) to those of J51. 146 However, the PN10:ITIC blend showed much higher D h and D e of 13.3 × 10 -4 cm 2 v _% s _% /8.7 × 10 -4 cm 2 v _% s _% compared to J51 (4.32 × 10 -4 cm 2 v _% s _% /3.74 × 10 -4 cm 2 v _% s _% ), indicating the much improved charge transport in PN10 due to the presence of selenophene side chains. Consequently, devices based on PN10:ITIC showed improved performance (J SC = 18.63 mA cm -2 ; V OC = 0.81 V; FF = 66.7%; PCE = 10.07%) compared to the devices based on J51:ITIC (J SC = 16.47 mA cm -2 ; V OC = 0.82 V; FF = 0.69; PCE = 9.26%).…”

Recent Advances Toward Highly Efficient Tandem Organic Solar Cells

“…The lone-pair electron on the 2-position nitrogen atom is more basic than the lone pairs on sulfur (in BT), which is prone to donate onto the triazole ring and results in higher LUMO levels and larger bandgaps of BTA-based polymers. [47][48][49] In 2013, our group reported a novel BTA-based polymer poly[(4,8-bis((2-butyloctyl)thio)benzo [1,2-…”

Structural engineering of pyrrolo[3,4-f]benzotriazole-5,7(2H,6H)-dione-based polymers for non-fullerene organic solar cells with an efficiency over 12%

“…It is known that balanced hole and electron mobilities can reduce bimolecular recombination to give high photocurrent and FF, which supports the higher J sc and FF of PBDT-F-TzBI:ITIC-based solar cells. 10,44,47,48 Exciton dissociation and charge recombination behavior…”