Jien Yang

Improving the stability of the perovskite solar cells by V2O5 modified transport layer film

This study describes a method for producing highly stable perovskite solar cells (PSCs). On the basis of conventional PSCs, a high-performance device was prepared using a vanadium pentoxide (V2O5) film to modify the poly(3,4-ethylene dioxy-thiophene)–poly(styrene sulfonate) (PEDOT:PSS) hole transport layer (HTL). The V2O5 modified layer prevents the acidic PEDOT:PSS film from etching the indium tin oxide (ITO) electrode and maintains the stability of the PSC structure. In addition, a 4,7-diphenyl-1,10-phenanthroline (Bphen) modified layer prevented the photoactive layer film from coming into direct contact with the Ag electrode to enhance the lifetime of the PSC stored in the air. In our study, a stable power conversion efficiency (PCE) of 15.49% was achieved using this method. Compared to the same type of devices, this type of device exhibited excellent performance and its stability was much higher than that of other device structures when stored in air. On modifying the transport layers to enhance the stability and longevity of the PSC, a method is provided for reference for further research.

Fabrication of In2O3/ZnO@Ag nanowire ternary composites with enhanced visible light photocatalytic activity

Herein, an In2O3/ZnO@Ag ternary photocatalyst was synthesized by a facile co-precipitation process. The results indicated that Ag nanowires were encapsulated by In2O3/ZnO compounds, and the obtained In2O3/ZnO@Ag photocatalyst showed strong absorption in the visible light region. The photoluminescence (PL) emission intensity gradually decreased for In2O3/ZnO@Ag as compared to that for the In2O3/ZnO composites and pure ZnO. The as-prepared In2O3/ZnO@Ag composites exhibited excellent visible light photocatalytic activities for degradation of organic contaminants (methyl orange and 4-nitrophenol). The enhancement of photocatalytic activity was ascribed to the extended visible light absorption region by Ag nanowires and the formation of close hetero-structure by the matched band structures of In2O3 and ZnO. Finally, a possible photocatalytic mechanism was proposed based on the matched energy band structure and active species trapping experiments.

Efficient and stable perovskite solar cells based on high-quality CH3NH3PbI3−xClx films modified by V2Ox additives

The method of preparing perovskite films in ambient air is of great importance to commercializing high-performance planar perovskite solar cells (PSCs). Herein, an efficient and stable inverted planar PSC has been prepared via a simple solution method in ambient air. A suitable vanadium oxide (V2Ox) aqueous solution is mixed with a CH3NH3PbI3−xClx precursor solution, resulting in an improvement in the CH3NH3PbI3−xClx film. Perovskite films with large crystal sizes could be obtained using V2Ox additives. The improvement in the performance of perovskite films is conducive to the separation and transmission of charge carriers. For PSCs, the highest power conversion efficiency (PCE) of 16.14% was obtained by controlling the proportion of V2Ox additives in ambient air. It is via a physical mechanism that V2Ox particles are dispersed in the perovskite crystal boundary, and the heterogeneous structure between CH3NH3PbI3−xClx and V2Ox is formed. In addition, the slow migration of iodide ions and stability of the perovskite films are also achieved. What merits more attention is that the PSCs with CH3NH3PbIxCl3−x:V2Ox (2.5 wt%) still maintain a high PCE after being stored for 1000 h, more than 70% of the initial one.

Electric-field assisted perovskite crystallization for high-performance solar cells

We develop an external-electric-field (EEF)-assisted annealing treatment to improve the photoelectric performance of planar organic–inorganic perovskite solar cells (PSCs). The new strategy can control the ion polarization orientation of perovskite films to obtain a good crystallization film and enhance the built-in electric field (BIF), which facilitates the effective promotion of charge separation and transport. Under an optimized treatment of up-EEF-assisted (2.5 V μm−1) annealing, the power conversion efficiency (PCE) of the inverted PSC is improved from 15.33% to 17.26%, and from 16.77% to 19.18% for regular PSCs, compared with the thermal-annealing-only process. The ion polarization and ferroelectricity in the perovskite layer induced by the EEF are intensively discussed. The finding in this work provides a new route to improve perovskite film quality and cell performance.

In situ polarization and dielectric property measurements of Pb(Zr0.52Ti0.48)O3 ferroelectric nanocrystals

Pb(Zr0.52Ti0.48)O3/polycarbonate (PZT/PC) composite films with different concentration of PZT ferroelectric nanocrystals are prepared. The polarization and dielectric relaxation behavior of PZT ferroelectric nanocrystals are characterized using in situ transmittance and X-ray diffraction (XRD) measurements for the first time. It’s found that 10% PZT/PC composite film has the largest orientation change and negligible dielectric relaxation after poling (the φ value of 13.8% is almost constant with time even for 168 h). Based on the XRD results, we consider that the preferential orientation of PZT nanocrystals to align in PC matrix after poling is [001] direction.