•The electrochemical reduction of nanocrystals is conducted in aqueous electrolyte.•The degradation of nanocrystals is avoided by fast scan in the redox process.•The fast charge transfer process on electrode indicates DNA–CTMA is conducting.The electrochemical redox behaviors of Cu(I) doped CdS nanoparticles in DNA–CTMA films are investigated in aqueous electrolyte. Both oxidation and reduction processes are electrochemically irreversible. The degradation of nanoparticles and the coupled chemical reactions in the electrochemical measurements can be avoided by fast potential scan as 1.5 V s−1. It is hardly found the residual O2 effect on the redox behavior of nanoparticles in DNA–CTMA film. The role of DNA–CTMA matrix in the charge transfer process between nanoparticles and the electrode is discussed.

A series of benzodithiophene (BDT) and benzothienothiophenedione (BTTDO) alternating wide-bandgap (WBG) copolymers, PBDT-O1, PBDT-S1 and PBDT-Se1, were designed and synthesized, in which heteroatoms (O, S and Se) were incorporated into the electron-deficient BTTDO motif. The effect of heteroatoms on the thermal stability, absorption spectra, energy level, charge carrier mobility, and photovoltaic properties of these WBG polymers was systematically studied. The results indicated that upon increasing the size of the heteroatoms, the maximum absorption peaks were red-shifted and the optical bandgap decreased. Solar cells with a conventional structure of ITO/PEDOT:PSS/polymers:PC70BM (1:1, w/w)/Ca/Al were fabricated. Among the three polymers, PBDT-S1 achieved the best photovoltaic performance, with a high power conversion efficiency (PCE) of 9.0%, with an open-circuit voltage (Voc) of 0.91 V, a short-circuit current (Jsc) of 12.99 mA cm−2, and an unprecedented fill factor (FF) of 74.9%.