Synthesis of Poly(benzothiadiazole‐co‐dithienobenzodithiophenes) and Effect of Thiophene Insertion for High‐Performance Polymer Solar Cells

Abstract

We describe herein the synthesis of novel donor-acceptor conjugated polymers with dithienobenzodithiophenes (DTBDT) as the electron donor and 2,1,3-benzothiadiazole as the electron acceptor for high-performance organic photovoltaics (OPVs). We studied the effects of strategically inserting thiophene into the DTBDT as a substituent on the skeletal structure on the opto-electronic performances of fabricated devices. From UV/Vis absorption, electrochemical, and field-effect transistor analyses, we found that the thiophene-containing DTBDT derivative can substantially increase the orbital overlap area between adjacent conjugated chains and thus dramatically enhance charge-carrier mobility up to 0.55 cm(2) V(-1) s(-1). The outstanding charge-transport characteristics of this polymer allowed the realization of high-performance organic solar cells with a power conversion efficiency (PCE) of 5.1 %. Detailed studies on the morphological factors that enable the maximum PCE of the polymer solar cells are discussed along with a hole/electron mobility analysis based on the space-charge-limited current model.

Dithieno[2,3‐d:2',3'‐d']benzo[1,2‐b:4,5‐b']dithiophene (DTBDAT)‐based copolymers for high‐performance organic solar cells

“…Scheme shows the synthesis of P(BDT‐TCNT) and P(DTBDAT‐TCNT ). The monomers were synthesized according to the methods in references . Polymers were obtained via a Stille coupling reaction using Pd 2 (dba) 3 /P(o‐tol) 3 (1/4) in chlorobenzene.…”

“…Such fused aromatic rings typically exhibit excellent intermolecular charge‐ transport properties because of the planarity of the backbone. There have been several reports describing the high charge‐carrier mobilities of these moieties when used in organic field‐effect transistors . Derivatives of DTBDAT exhibit relatively low HOMO levels and large band gaps compared with those of other fused aromatic rings, which suggests that the DTBDAT motif is a particularly stable organic semiconductor.…”

Thieno[3,4‐c]pyrrole‐4,6‐dione‐Based Small Molecules for Highly Efficient Solution‐Processed Organic Solar Cells

“…The difference in the hole mobility values is one order of magnitude, which also indicates that the hole-transporting abilities of TBDT-TTPD enable high hole mobility in blended films. [30] The photovoltaic characteristics of small molecules were investigated by using the conventional structure of ITO/PEDOT/PSS/BT-TPD and TBDT-TTPD/PCBM/LiF/Al . To optimize the photovoltaic conditions, devices with different small molecule/acceptor weight ratios, fullerene derivative (PC 61 BM and PC 71 BM), solvent, and thermal annealing (from 100 to 160 8C) were examined (detailed photovoltaic data are presented in the Supporting Information).…”

Dithieno[2,3‐d:2′,3′‐d′]naphtho[2,1‐b:3,4‐b′]dithiophene based medium bandgap conjugated polymers for photovoltaic applications

“…Recently, polycyclic thienoacenes with larger coplanar core and more extended conjugation length are complimented by an extensive set of advantageous characteristics, such as enhanced charge‐carrier mobilities, decreased band gaps, effective exciton separation into free charge carriers of the corresponding conjugated polymers (CPs), all of which are essential to achieve high device performance . For example, in 2010, You and coworkers prepared a donor–acceptor polymer (PQTN‐BT) based on quadrathienonaphthalene (QTN), and the polymer showed a PCE over 2% in corresponding polymer solar cells (PSCs) .…”

“…Furthermore, Hou and coworkers prepared a CP (PDTT) based on 5,10‐di(2‐hexyldecyloxy)dithieno[2,3‐d:2′,3′‐d′]benzo[1,2‐b:4,5‐b′]dithiophene (DTBDT) and obtained a PCE of 3.64% in corresponding PSCs . Lately, with DTBDT as the electron donor and 2,1,3‐benzothiadiazole as the electron acceptor, Kwon and coworkers synthesized a CP (PDTBDAT‐BZ), and received a PCE of 5.1% based on the CP . In addition, Yu and coworkers presented a series of CPs based on dithieno[2,3‐d:2′,3′‐d′]benzo[1,2‐b:4,5‐b′]dithiophene (DBD), the PCEs of 3.9 ∼ 7.6% have been achieved in the PSCs from the CPs .…”