Search Results (4)

A perovskite photo-sensor is promising for a lightweight, thin, flexible, easy-to-coat fabrication process, and a higher incident photon-to-current conversion efficiency. We have investigated perovskite photo-sensors with a solution-processed compact TiO₂ under a low-temperature process and an ultra-thin polyethylenimine ethoxylated (PEIE) as an electron injection layer. The TiO₂ film is grown from an aqueous solution of titanium tetrachloride (TiCl₄) at 70 °C by a chemical bath deposition method. For an alternative process, the ultra-thin PEIE is spin coated on the TiO₂ film. Then, the perovskite layer is deposited on the substrate by the one- or two-step methods in the glovebox. Next, a hole transport layer of 2,2,7,7-tetrakis(N,N-di-p-methoxyphenylamine)-9, 9-spiro-bifluorene (Spiro-OMeTAD) solution is spin coated. The fabricated device structure is a photodiode structure of FTO/TiO₂/(without or with) PEIE/(one- or two-step) perovskite layer/Spiro-OMeTAD/Au. For the sensing characteristics, a ratio of photo-to-dark-current density was 2.88 × 10⁴ for the device with PEIE layer. In addition, a power-law relationship is discussed. Full article

In this work, we studied inverted organic solar cells based on bulk heterojunction using poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C71-butyric acid methyl ester (P3HT:PCBM) as an active layer and a novel cathode buffer bilayer consisting of tin dioxide (SnO₂) combined with polyethylenimine-ethoxylated (PEIE) to overcome the limitations of the single cathode buffer layer. The combination of SnO₂ with PEIE is a promising approach that improves the charge carrier collection and reduces the recombination. The efficient device, which is prepared with a cathode buffer bilayer of 20 nm SnO₂ combined with 10 nm PEIE, achieved Jsc = 7.86 mA/cm², Voc = 574 mV and PCE = 2.84%. The obtained results exceed the performances of reference solar cell using only a single cathode layer of either SnO₂ or PEIE. Full article

A series of lead-halide based hybrid polyelectrolytes was prepared and used as interfacial layers in organic solar cells (OSCs) to explore their effect on the energy band structures and performance of OSCs. Nonconjugated polyelectrolytes based on ethoxylated polyethylenimine (PEIE) complexed with PbX₂ (I, Br, and Cl) were prepared as polymeric analogs of the perovskite semiconductors CH₃NH₃PbX₃. The organic/inorganic hybrid composites were deposited onto Indium tin oxide (ITO) substrates by solution processing, and ultraviolet photoelectron spectroscopy (UPS) measurements confirmed that the polyelectrolytes allowed the work function of the substrates to be controlled. In addition, X-ray photoelectron spectroscopy (XPS) results showed that Pb(II) halide complexes were present in the thin film and that the Pb halide species did not bond covalently with the cationic polymer and confirmed the absence of additional chemical bonds. The composite ratio of organic and inorganic materials was optimized to improve the performance of OSCs. When PbBr₂ was complexed with the PEIE material, the efficiency increased up to 3.567% via improvements in open circuit voltage and fill factor from the control device (0.3%). These results demonstrate that lead-halide based polyelectrolytes constitute hybrid interfacial layers which provide a novel route to control device characteristics via variation of the lead halide composition. Full article

High performance flexible inverted organic solar cells (OSCs) employing the low temperature cathode buffer bilayer combining the aqueous solution-processed ZnO and polyethylenimine ethoxylated (PEIE) are investigated based on Poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C₆₁-butryric acid methyl ester (P3HT:PC₆₁BM) and Poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexy)carbonyl]thieno[3,4-b]thiophenediyl}):[6,6]-phenyl-C₇₁-butyric acid methyl ester (PTB-7:PC₇₁BM) material systems. It is found that, compared with pure ZnO or PEIE cathode buffer layer (CBL), the proper combination of low-temperature processed ZnO and PEIE as the CBL enhanced the short circuit current density (J_SC), resulting in better device performance. The increased J_SC results from the enhanced electron collection ability from the active layer to the cathode. By using the ZnO/PEIE CBL, a power conversion efficiency (PCE) as high as 4.04% for the P3HT:PC₆₁BM flexible device and a PCE as high as 8.12% for the PTB-7:PC₇₁BM flexible device are achieved, which are higher than the control devices with the pure ZnO CBL or pure PEIE CBL. The flexible inverted OSC also shows a superior mechanical property and it can keep 92.9% of its initial performance after 1000 bending cycles with a radius of 0.8 cm. These results suggest that the combination of the low temperature aqueous solution processed ZnO and PEIE can be a promising cathode buffer bilayer for flexible inverted OSCs. Full article