Miao Duan

Enhanced electronic properties in CH3NH3PbI3via LiCl mixing for hole-conductor-free printable perovskite solar cells

By mixing perovskite MAPbI3 (MA = CH3NH3+) with LiCl, an effective one-step drop-coating approach was developed to improve the performance of hole-conductor-free printable perovskite solar cells. The LiCl-mixed perovskite exhibited superior electronic properties because of the improved conductivity of the perovskite layer enabling faster electron transport. LiCl-mixing also improved the crystallinity and morphology of the perovskite layer. As a consequence, perovskite solar cells prepared using the LiCl-mixed perovskite as the light harvester produced higher performances compared with the unmixed perovskite, improving the power conversion efficiency from 10.0% to 14.5%.

Effect of guanidinium on mesoscopic perovskite solar cells

Hole-conductor-free printable mesoscopic perovskite solar cells based on a TiO2/ZrO2/carbon architecture have attracted much attention due to their low material cost and simple fabrication process. However, the micron-thick mesoporous scaffold always challenges the filling of the perovskite absorber and causes significant charge carrier loss. We employ a multifunctional additive of guanidinium chloride (GuCl) to improve the quality of the CH3NH3PbI3 perovskite absorber, and suppress the recombination reaction in the device. It is found that GuCl effectively enhances the charge carrier lifetimes of the perovskite, and suppresses charge carrier loss in the hole-conductor-free devices. Correspondingly, the open-circuit voltage (VOC) of the device is significantly enhanced from 0.88 V to 1.02 V.

Evidence for Aggregation-Induced Emission from Free Rotation Restriction of Double Bond at Excited State

This paper reports that cis-TPE dicycles emit strong fluorescence, while the gem dicycles show almost no emission in solution, demonstrating that the free rotation restriction of the double bond at the excited state is the key factor for AIE effects.

Boron-Doped Graphite for High Work Function Carbon Electrode in Printable Hole-Conductor-Free Mesoscopic Perovskite Solar Cells

Work function of carbon electrodes is critical in obtaining high open-circuit voltage as well as high device performance for carbon-based perovskite solar cells. Herein, we propose a novel strategy to upshift work function of carbon electrode by incorporating boron atom into graphite lattice and employ it in printable hole-conductor-free mesoscopic perovskite solar cells. The high-work-function boron-doped carbon electrode facilitates hole extraction from perovskite as verified by photoluminescence. Meanwhile, the carbon electrode is endowed with an improved conductivity because of a higher graphitization carbon of boron-doped graphite. These advantages of the boron-doped carbon electrode result in a low charge transfer resistance at carbon/perovskite interface and an extended carrier recombination lifetime. Together with the merit of both high work function and conductivity, the power conversion efficiency of hole-conductor-free mesoscopic perovskite solar cells is increased from 12.4% for the pristine graphite electrode-based cells to 13.6% for the boron-doped graphite electrode-based cells with an enhanced open-circuit voltage and fill factor.

Spacer improvement for efficient and fully printable mesoscopic perovskite solar cells

Highly dispersible TiO2@ZrO2 nanoparticles are synthesized to prepare an ultra-flat and crack-free spacer film, leading to an enhanced insulating ability compared to a conventional spacer. The average power conversion efficiency of fully printable mesoscopic perovskite solar cells is improved from 10.2% to 12.5%, and the highest steady output power conversion efficiency is 13.8%.

Mixed (5-AVA)xMA1−xPbI3−y(BF4)y perovskites enhance the photovoltaic performance of hole-conductor-free printable mesoscopic solar cells

We report on a simple one-step solution processing strategy to fabricate new stable mixed cation/mixed halide (5-AVA)xMA1−xPbI3−y(BF4)y perovskite solar cells. The results showed that the power conversion efficiency (PCE) of the optimized mixed (5-AVA)0.034MA0.966PbI2.95(BF4)0.05 perovskite solar cells was substantially increased to 15.5% with a remarkably high VOC of 0.97 V. We have analyzed different mixed perovskites focusing on the characterization of the charge recombination by means of intensity-modulated photovoltage spectroscopy. In addition, our study discloses that the incorporation of MABF4 into the (5-AVA)0.034MA0.966PbI3 perovskite helps to reduce the charge recombination in the mixed perovskite cells, thus improving the open circuit voltage of the device. Furthermore, the new mixed perovskite was demonstrated to produce high-quality perovskite crystals and enhance the conductivity of the mixed perovskite.

A Multifunctional Bis-Adduct Fullerene for Efficient Printable Mesoscopic Perovskite Solar Cells

Printable mesoscopic perovskite solar cells (PMPSCs) have exhibited great attractive prospects in the energy conversion field due to their high stability and potential scalability. However, the thick perovskite film in the mesoporous layers challenges the charge transportation and increase grain boundary defects, limiting the performance of the PMPSCs. It is critical not only to improve the electric property of the perovskite film but also to passivate the charge traps to improve the device performance. Herein we synthesized a bis-adduct 2,5-(dimethyl ester) C60 fulleropyrrolidine (bis-DMEC60) via a rational molecular design and incorporated it into the PMPSCs. The enhanced chemical interactions between perovskite and bis-DMEC60 improve the conductivity of the perovskite film as well as elevate the passivation effect of bis-DMEC60 at the grain boundaries. As a result, the fill factor (FF) and power conversion efficiency (PCE) of the PMPSCs containing bis-DMEC60 reached 0.71 and 15.21%, respectively, significantly superior to the analogous monoadduct derivative (DMEC60)-containing and control devices. This work suggests that fullerene derivatives with multifunctional groups are promising for achieving high-performance PMPSCs.

Efficient hole-conductor-free printable mesoscopic perovskite solar cells based on hybrid carbon electrodes

The exceptional photovoltaic properties demonstrated for organic-inorganic hybrid lead halide perovskites have attracted tremendous attention around the world. The intriguing optoelectrical characteristics include strong absorption coefficient, high carrier mobility and long charge diffusion length. The power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have now been boosted up to a certified 22.7% within a few years. Based on ambipolar type carrier transport properties of the perovskites, hole-conductor-free (HTMfree) PSCs have been developed, which simplifies the configuration of the devices. Previously, our group has developed a carbon based HTM-free printable mesoscopic PSC and achieved a certified PCE of 12.8 % with high stability. Herein, we reported a new hybrid carbon electrode based on ultrathin graphite/carbon black for HTM-free printable mesoscopic PSCs, and obtained a PCE of 13.83%.