Prof. Zhang Deqing and colleagues from Institute of Chemistry, Chinese Academy of Sciences have reported a series strategies through modifications of side-chains in organic semiconductors for charge mobility enhancement with the help of 1W1A of Beijing Synchrotron Radiation Facility. In this year, firstly, they successfully incorporated thymine groups in the side chains of DPP-based conjugated polymer PDPP4T-T. The studies reveal that thin film of PDPP4T-T exhibits improved crystallinity and higher charge mobility compared with analogous polymers with pure alkyl chains. This is attributed to the formation of H-bonding among thymine groups demonstrated by GIWAXS studies (1W1A of Beijing Synchrotron Radiation Facility), which could strengthen interchain interactions and thus facilitate ordered packing of polymer chains (Chem. Mater. 2019, 31, 1800). Secondly, they establish a new design strategy for photoresponsive conjugated polymers by incorporating photochromic units (azobenzene) into the flexible side alkyl chains. They show that azobenzene groups in the side chains of the DPP (PDAZO) can undergo trans-/cis- photoisomerization in fully reversible and fast manner. Optically tunable FETs with bistable states were successfully fabricated with thin films of PDAZO. Additionally, thin film charge mobility of PDAZO can be reversibly modulated by alternating UV and visible light irradiations. On the basis of theoretical calculations and GIWAXS data (1W1A of Beijing Synchrotron Radiation Facility), they hypothesize that the dipole moment and configuration changes associated with the trans-/cis- photoisomerization of azobenzene groups in PDAZO can affect the respective intra-chain and inter-chain charge transporting, which is responsible for the optically tunable behavior for FETs with thin films of PDAZO (Adv. Funct. Mater. 2019, 29, 1807176).

Fig. Chemical structures of PDPP4T-T (above) and PDAZO (below)

Article:

1.Yizhou Yang, Zitong Liu,* Liangliang Chen, Jingjing Yao, Gaobo Lin, Xisha Zhang, Guanxin Zhang, and Deqing Zhang* Conjugated Semiconducting Polymer with Thymine Groups in theSide Chains: Charge Mobility Enhancement and Application for Selective Field-Effect Transistor Sensors toward CO and H2S. Chem. Mater. 2019, 31, 1800.

2.Jianwu Tian, Lulu Fu, Zitong Liu,* Hua Geng, Yanan Sun, Gaobo Lin, Xisha Zhang, Guanxin Zhang, and Deqing Zhang*. Optically Tunable Field Effect Transistors with Conjugated Polymer Entailing Azobenzene Groups in the Side Chains. Adv. Funct. Mater. 2019, 29, 1807176.