At an elevated temperature of 90 °C, a chemical bath deposition using an aqueous solution of Zn(NO₃)₂·6H₂O and (CH₂)₆N₄ resulted in the formation of both nanoflowers and microrods of ZnO on F-doped SnO₂ glass with a seed layer. The nanoflowers and microrods were sensitized with dyes for application to the photoelectrodes of dye-sensitized solar cells (DSSCs). By extending the growth time of ZnO, the formation of nanoflowers was reduced and the formation of microrods favored. As the growth time was increased from 4 to 6 and then to 8 h, the open circuit voltage (V_oc) values of the DSSCs were increased, whilst the short circuit current (J_sc) values varied only slightly. Changes in the dye-loading amount, dark current, and electrochemical impedance were monitored and they revealed that the increase in V_oc was found to be due to a retardation of the charge recombination between photoinjected electrons and I₃⁻ ions and resulted from a reduction in the surface area of ZnO microrods. A reduced surface area decreased the dye contents adsorbed on the ZnO microrods, and thereby decreased the light harvesting efficiency (LHE). An increase in the electron collection efficiency attributed to the suppressed charge recombination counteracted the decreased LHE, resulting in comparable J_sc values regardless of the growth time.

By simple soaking titanium dioxide (TiO₂) films in an aqueous Na₂S solution, we could prepare surface-modified photoanodes for application to dye-sensitized solar cells (DSSCs). An improvement in both the open-circuit voltage (V_oc) and the fill factor (FF) was observed in the DSSC with the 5 min-soaked photoanode, compared with those of the control cell without any modification. The UV–visible absorbance spectra, UPS valence band spectra, and dark current measurements revealed that the Na₂S modification led to the formation of anions on the TiO₂ surface, and thereby shifted the conduction band edge of TiO₂ in the negative (upward) direction, inducing an increase of 29 mV in the V_oc. It was also found that the increased FF value in the surface-treated device was attributed to an elevation in the shunt resistance.

We report a highly effective surface treatment method for planar-type Sb2S3 solar cells by employing a Cs2CO3-modified compact TiO2 (c-TiO2) electron transport layer. It is found that surface treatment using a Cs2CO3 solution can shift the work function of c-TiO2 upward and reduce its surface roughness. As a result, compared with the power conversion efficiency of untreated solar cells, that of the treated solar cells with a glass/FTO/c-TiO2(/Cs2CO3)/Sb2S3/P3HT/Au structure significantly improved from 2.83 to 3.97%. This study demonstrates that the introduction of Cs2CO3 on a c-TiO2 layer is a simple and efficient way to adjust the work function of the electron transport layer and fabricate high-performance planar-type Sb2S3 solar cells.

CsPbIBr₂, a cesium-based all-inorganic halide perovskite (CsPe), is a very promising alternative material to mainstream organic–inorganic hybrid halide perovskite (HPe) materials owing to its exceptional moisture stability, thermal stability, and light stability. However, because of the wide band gap (2.05 eV) of CsPbIBr₂, it has a low power conversion efficiency (PCE), which hinders its application in highly efficient solar cells. In this study, a facile nanoimprinted one-dimensional grating nanopattern (1D GNP) formation on mesoporous TiO₂ (mp-TiO₂) photoelectrodes was introduced to improve the effective light utilization and enhance the performance of CsPbIBr₂ perovskite solar cells (PSCs). The 1D GNP structure on the mp-TiO₂ layer increases the light absorption efficiency by diffracting the unabsorbed light into the active mp-TiO₂ and CsPbIBr₂ layers as well as increasing the charge separation and collection due to the extended interfacial contact area between the mp-TiO₂ and CsPbIBr₂ layers. Consequently, both the current density (J_SC) and the fill factor (FF) of the fabricated cells improved, leading to over a 20% enhancement in the solar cell’s PCE. Thus, this periodic grating structure, fabricated by simple nanoimprinting, could play an important role in the large-scale production of highly efficient and cost-effective Cs-based PSCs.

All-inorganic metal halide perovskite nanocrystals (IPeNCs) have become one of the most promising luminescent materials for next-generation display and lighting technology owing to their excellent color expression ability. However, research on IPeNCs with stable blue emission is limited. In this paper, we report stable blue emissive all-bromide IPeNCs obtained through a modified ligand-assisted reprecipitation method using an ultraviolet (UV)-curable prepolymer as the anti-solvent at a low temperature. We found that the blue emission originates from quantum-confined CsPbBr₃ nanoparticles formed together with the colorless wide-bandgap Cs₄PbBr₆ nanocrystals. When the temperature of the prepolymer was increased from 0 to 50 °C, CsPbBr₃ nanoparticles became larger and more crystalline, thereby altering their emission color from blue to green. The synthesized all-bromide blue-emitting IPeNC solution remained stable for over 1 h. It also remained stable when it was mixed with the green-emitting IPeNC solution. By simply exposing the as-synthesized IPeNC–prepolymer solutions to UV light, we formed water-stable composite films that emitted red, green, blue, and white colors. We believe that this synthetic method can be used to develop color-emitting composite materials that are highly suitable for application as the color conversion films of full-color liquid crystal display backlight systems and lighting applications.