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Converting light energy to electrical energy in photovoltaic devices relies on the photogenerated electrons and holes separated by the built-in potential in semiconductors. Photo-excited electrons in metal electrodes are usually not considered in this process. Here, we report an enhanced photovoltaic effect in the ferroelectric lanthanum-modified lead zirconate titanate (PLZT) by using low work function metals as the electrodes. We believe that electrons in the metal with low work function could be photo-emitted into PLZT and form the dominant photocurrent in our devices. Under AM1.5 (100 mW/cm2) illumination, the short-circuit current and open-circuit voltage of Mg/PLZT/ITO are about 150 and 2 times of those of Pt/PLZT/ITO, respectively. The photovoltaic response of PLZT capacitor was expanded from ultraviolet to visible spectra, and it may have important impact on design and fabrication of high performance photovoltaic devices based on ferroelectric materials.

Considering the environment protection, “green” materials are increasingly explored for photovoltaics. Here, we developed a kind of quantum dots solar cell based on nitrogen-doped carbon dots. The nitrogen-doped carbon dots were prepared by direct pyrolysis of citric acid and ammonia. The nitrogen-doped carbon dots’ excitonic absorption depends on the N-doping content in the carbon dots. The N-doping can be readily modified by the mass ratio of reactants. The constructed “green” nitrogen-doped carbon dots solar cell achieves the best power conversion efficiency of 0.79 % under AM 1.5 G one full sun illumination, which is the highest efficiency for carbon dot-based solar cells.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1231-1) contains supplementary material, which is available to authorized users.

The nonradiative recombination of electrons and holes has been identified as the main cause of energy loss in hybrid organic-inorganic perovskite solar cells (PSCs). Sufficient built-in field and defect passivation can facilitate effective separation of electron-hole pairs to address the crucial issues. Fort he first time,w ei ntroduce ah omochiral molecular ferroelectric into aP SC to enlarge the built-in electric field of the perovskite film, therebyf acilitating effective charge separation and transportation. As ac onsequence of similarities in ionic structure,t he molecular ferroelectric component of the PSC passivates the defects in the active perovskite layers, therebyi nducing an approximately eightfold enhancement in photoluminescence intensity and reducing electron trap-state density.The photovoltaic molecular ferroelectric PSCs achieve apower conversion efficiency as high as 21.78 %.

It is a challenge to grow perovskite films with large crystalline grains and a full coverage on the surface of an organic compound film by a solution process. Herein, we for the first time introduce environmental‐friendly urea into PbI2 precursor to mediate the perovskite film growth and crystallization on the top of PEODT:PSS for efficient inverted solar cells. This method attains high‐quality perovskite films with large‐size grains of over 2 μm and a full coverage. This enables us to fabricate the inverted perovskite solar cells showing a maximum efficiency of 18.01% with a fill factor of 82.29% and a stabilized efficiency of 17.56%. Infrared spectroscopy and scanning electron microscopy images demonstrate that urea is coordinated with PbI2 to form PbI2 · OC(NH2)2 complex, resulting in large PbI2 flakes by a slow crystallization. The large PbI2 flake with fewer nucleation sites is conducive to forming monolithic perovskite grains. Further investigation indicates that CH3NH3I · PbI2 · OC(NH2)2 complex is formed as an intermediate phase, which retards the crystallization process of the perovskite films. These factors lead to a high‐quality perovskite film with large grain size and excellent crystallinity.