Shorter alkyl chain in thieno[3,4-c]pyrrole-4,6-dione(TPD)-based large bandgap polymer donors – Yield efficient non-fullerene polymer solar cells

Typically,conjugated polymers are composed of conjugated backbones and alkyl side chains.In this contribution,a cost-effective strategy of tailoring the length of alkyl side chain is utilized to design highperforming thieno[3,4-c]pyrrole-4,6-dione(TPD)-based large bandgap polymer donors PBDT-BiTPD(Cχ)(χ=48,52,56),in which x represents the alkyl side chain length in term of the total carbon number.A combination of light absorption,device,and morphology examinations make clear that the shorter alkyl side chains yield(i) higher crystallinity and more predominant face-on crystallite orientation in their neat and BHJ blend films,(ii) higher charge mobilities(6.7×10^(-4) cm~2 V^(-1) s^(-1) for C48 vs.3.2×10^(-4) cm~2 V^(-1) s^(-1) for C56),and negligible charge recombination,consequently,(iii) significantly improved fill-factor(FF) and short current(J_(SC)),while almost the same open circuit voltage(V_(OC)) of ca.0.82 V in their corresponding BHJ devices.In parallel,as alkyl side chain lengths decrease from C56 to C48,power conversion efficiencies(PCEs) increased from 7.8% for C56 to 11.1% for C52,and further to14.1% for C48 in their BHJ solar cells made with a narrow bandgap non-fullerene acceptor Y6.This systematic study declares that shortening the side chain,if providing appropriate solubility in device solution processing solvents,is of essential significance for developing high-performing polymer donors and further improving device photovoltaic performance.

Low-bandgap conjugated polymers based on benzodipyrrolidone with reliable unipolar electron mobility exceeding 1 cm^(2) V^(-1)s^(-1)

The employment of an intrinsic quinoidal building block,benzodipyrrolidone(BDP),on constructing conjugated polymers(PBDP-2F and PBDP-2CN)with high electron mobility and unipolar transport characteristic in polyethylenimine ethoxylated(PEIE)modified organic field-effect transistors(OFETs)is reported.The intrinsic quinoidal characteristic and excellent coplanarity of BDP can lower the lowest unoccupied molecular orbital(LUMO)levels and improve ordered interchain packing of the resulting polymers in solid states,which are favorable for electron-injection and transport.By using PEIE as the interlayer to block the hole injection,unipolar n-type transport characteristics with high electron mobility of 0.58 and 1.01 cm^(2) V^(-1)s^(-1)were achieved by the OFETs based on PBDP-2F and PBDP-2CN,respectively.More importantly,the extracted mobilities are highly reliable with the reliability factor of above 80%.To the best of our knowledge,PBDP-2CN is the very first quinoid-based conjugated polymer with reliable electron mobility exceeding 1 cm^(2) V^(-1)s^(-1).This work represents a significant step in exploring intrinsic quinoidal CPs for application in n-channel OFETs and logic complementary circuits.