Development of a High-Performance Donor–Acceptor Conjugated Polymer: Synergy in Materials and Device Optimization

Abstract

The development of a high performance polymer PBDT-BT for bulk heterojunction solar cell devices is summarized. The polymer was first synthesized by Stille polycondensation and solar cell devices in conventional geometry was optimized through the use of a lithium salt cathode interlayer reaching 6% power conversion efficiency. Improvements were made to the synthesis of the polymer using Suzuki polycondensation giving high molecular weight material in the Mn 100 kg/mol range. Further device optimization in inverted geometry gave power conversion efficiency of over 9%. The synthesis scalability as well as the batch-to-batch reproducibility of the polymer were extensively investigated. ASSOCIATED CONTENT Supporting Information. Experimental procedures on synthesis of the polymers, characterization data and details on device fabrication and testing. This material is available free of charge via the Internet at http://pubs.acs.org.

Preparation of semi‐alternating conjugated polymers using direct arylation polymerization (DArP) and improvement of photovoltaic device performance through structural variation

“…If alkyl chains are present on the acceptor unit, then the donor unit should possess alkyl chains that do not inhibit polymer: fullerene miscibility, such as the randomized polymers P4 and P8 . This is evident with the results described herein, the discussion regarding polymer:fullerene miscibility, and with the architectures of current, high‐performing polymers …”

“…The fill‐factor values obtained (0.57–0.63) are some of the highest reported for polymers prepared using DArP, likely resultant of improvements in the morphology of the active layer in regards to the polymer donor's interactions with the fullerene‐acceptor. More specifically, it is envisioned that the larger 2‐hexyldecyl alkoxy chains, accompanied by the alkyl chains on the DTTPD or DTDPP acceptors, causes an increase in steric interactions between the polymer and the fullerene leading to a decrease in miscibility with the PCBM acceptor . With PPDTBT, alkyl substituents are located only on the benzene donor unit.…”

High performance p-type molecular electron donors for OPV applications via alkylthiophene catenation chromophore extension

“…The bis-borylated product was isolated by precipitation on addition of isopropanol (IPA), and an analytically pure material isolated by filtration in excellent yields >90%, Scheme 4. This simplified purification is in direct contrast with reported procedures for the bis-iodinated or bis-stannylated analogues [20–21]. …”

Molecular design of interfacial layers based on conjugated polythiophenes for polymer and hybrid solar cells

“…Low WF alkali earth metals including Mg (−3.7 eV), Ba (−2.7 eV) and Ca (−2.9 eV) and alkali metal compounds such as Cs 2 CO 3 and LiF (WF < 3.0 eV) have been used extensively as the CIL to reduce the WF of the cathode for more efficient electron extraction. However, these pure metals are air‐ and moisture‐sensitive and can be easily oxidized, which significantly decreases the stability of OPV devices .…”