Benzo[1,2-b:4,5-b′]dithiophene-based conjugated polymers: band gap and energy level control and their application in polymer solar cells

Abstract

To pursue high power conversion efficiency (PCE) of polymer solar cells (PSCs), more and more new active layer materials, especially polymeric photovoltaic materials, have been developed in the past several years, and benzo[1,2-b:4,5-b 0 ]dithiophene (BDT) plays a very important role in these polymer materials. The applications of these new polymer materials boost the PCE of polymer solar cells greatly, and recent results indicate that 7-8% PCEs have been achieved by using BDT-based polymers. In this review, we summarize the recent works related to BDT-based polymers for the applications in PSCs and try to reveal the correlations of molecular structures of BDT-based polymers with their band gaps and molecular energy levels.

Structure and Morphology Control in Thin Films of Conjugated Polymers for an Improved Charge Transport

“…Firstly, extending the conjugation system and strengthening intra-chain and inter-chain interaction is a direct way to improve electronic properties. Based on the classic conjugated polymers such as P3ATs (P1), a straight strategy is inserting more conjugated moieties [3,82] such as carbon double bond (-HC=CH-, P2) [83][84][85], unsubstituted multiple or fused aromatic rings (i.e., thiophenes and thieno[3,2-b]thiophene, etc., P3-P7) [13,14,16,37,82,[86][87][88][89][90][91], other heterocyclic rings containing nitrogen(and sulfur) (P8 and P9) or selenium atoms (P10) [13,15,81,[92][93][94][95][96][97] and their combination (P11) [98]. Thus, the intra-chain conjugation is extended and strengthened by coupling with the more conjugated moieties, and the conjugation length is elongated due to the improved planarity.…”

“…Compared with inorganic semiconductors and organic π-conjugated small molecules, the family of conjugated polymers has great advantages in its low weight, easy solution-processing and suitability to industrial manufacturing of large-area devices such as roll-to-roll routes [8][9][10]. Thus, many groups of conjugated polymers have been synthesized [3,[11][12][13][14][15][16] and a extremely high carrier mobility of 12.04 cm in FETs without doping [17] and power conversion efficiency of 8.67% in single junction OPVs [18] have been realized among them, which shows a brilliant prospects of them as the next-generation electronic materials. Therefore, understanding the correlations between the intrinsic properties of conjugated polymers, the features of thin film and the performance of corresponding electronic devices become crucial to guide the synthesis of more excellent materials and achievement of better electronic properties.…”

Influence of the alkyl substitution position on photovoltaic properties of 2D-BDT-based conjugated polymers

“…Design, synthesis and applications of novel conjugated polymers for polymer solar cells (PSCs) have received substantial attention over the past decades [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Significant improvements have been achieved in understanding the correlations between polymer structure and photovoltaic performance, which have helped to boost the power conversion efficiency (PCE) over 7% in several well-known backbones, such as benzodithiophene (BDT) and thienothiophene (TT) (PBDT-TT) [15][16][17][18][19][20][21][22][23][24][25][26][27][28], BDT and benzothiadiazole (BT) (PBDT-BT) [29,30], BDT and thienopyrroledione (TPD) (PBDT-TPD) [31], etc.…”

Naphthodithiophene-Based Semiconducting Materials for Applications in Organic Solar Cells

“…Among various electron donor units, benzo[1,2-b:4,5-b′]dithiophene (BDT) [53] (Figure 1) has shown great sucess in creating high performance solar cell materials [54], the BDTcontaining materials represent one of the most important classes of organic semiconductors for OSC applications [2,31]. The fused and symmetric structure of BDT units leads to high degree of backbone coplanarity, and tight and regular packing.…”