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The environment friendly Cu2ZnSnSe4 (CZTSe) quantum dot-sensitized solar cells (QDSSCs) has become one of the most promising photovoltaic technologies due to its earth-abundant component and excellent photoelectric properties. However, the power conversion efficiency (PCE) is far behind other high-efficiency chalcogenide sensitizer systems and the main obstacle can be attributed to the inappropriate conduction band position relative to the TiO2 films. Herein, we developed a partial substitution approach to transform CZTSe QDs to Cu2Zn(SnxGe1−x)Se4 (CZTGSe) QDs to resolve the CBM mismatch problem in QDSSCs. The CZTGSe QDs with narrow size distribution were synthesized via one-step method and Ge/(Ge+Sn) ratios were prepared. It is found that the introduction of Ge upshifts the CBM and broadens the band gap of CZTGSe QDs. Benefiting from the enhanced driving force of photoelectron injection and depressed charge recombination at TiO2/QDs/electrolyte interface, the short-circuit current (Jsc) and open-circuit voltage (Voc) of Ge-substituted QDSSCs are synchronously improved and the PCE of the 30% Ge content device finally is increased from 3.83 to 4.42%. This Ge-assisted band engineering approach solves the main obstacle for the further development of panchromatic CZTGSe QDSSCs. [ABSTRACT FROM AUTHOR]

Due to the simple preparation technology and appropriate crosslinking process, polyurethane was selected as the host polymer for the preparation of organic electro-optics (EO) materials. The synthesis and crosslinking process of polyurethane demanded the nonlinear optical (NLO) chromophore possessing strong stability in acid environment. Fortunately, after the introduction of azo group in the electronic bridge, the stability of this kind of chromophores in acidic environment was improved greatly. Polyurethane EO polymers and EO films based on this kind of chromophore were prepared successfully. The crosslinking process was monitored by infrared spectroscopy clearly. The crosslinking process has direct relationship with the molecular weight of the crosslinkers. Crosslinker of triethanolamine with small molecular weight showed low crosslinking temperature (80 °C) and short crosslinking time (20 min). The crosslinking temperature and time was improved to 140 °C and 60 min based on Poly(bisphenol A glycidyl ether aniline) (BPAN) crosslinker with large molecular weight. More importantly, this kind of EO polymers showed us large second order nonlinear optical coefficients (76.1 pm/V) and good long term stability (130 °C). [ABSTRACT FROM AUTHOR]