A facile and effective approach to enhance the performance and stability of perovskite solar cells is proposed by using a solution-processed cetyltrimethylammonium bromide (CTAB)-doped [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) film as a cathode interfacial layer.

We present a solution-processed blue organic light-emitting diode (OLED) with markedly high current efficiency of 41.2 cd A⁻¹ at 100 cd m⁻² and 31.1 cd A⁻¹ at 1000 cd m⁻². The high efficiency was partly attributed to the use of a molecular host, 3,5-di(9H-carbazol-9-yl)tetraphenylsilane, which possesses a wide triplet band gap, high carrier mobility, ambipolar transport property and high glass transition temperature. Besides the intrinsically good physical properties, the solution-process also played an important role in fabricating the high-efficiency device, since it could make the molecular distribution of host and guest homogeneous in the emissive layer. Moreover, the device efficiency at higher brightness could be markedly enhanced by using an electron-blocking layer. As the microlens was introduced on the glass substrate to enhance the light outcoupling, the resultant device efficiency of the blue OLED further increased to 50.1 cd A⁻¹ at 100 cd m⁻² and 37.3 cd A⁻¹ at 1000 cd m⁻².

Nano-structured CuO-Cu2O complex thin film-based perovskite solar cells were fabricated on an indium tin oxide (ITO)-coated glass and studied. Copper (Cu) thin films with a purity of 99.995 % were deposited on an ITO-coated glass by magnetron reactive sputtering. To optimize the properties of the nano-structured CuO-Cu2O complex thin films, the deposited Cu thin films were thermally oxidized at various temperatures from 300 to 400 °C. A CH3NH3PbI3 perovskite absorber was fabricated on top of CuO-Cu2O complex thin film by a one-step spin-coating process with a toluene washing treatment. Following optimization, the maximum power conversion efficiency (PCE) exceeded 8.1 %. Therefore, the low-cost, solution-processed, stable nano-structured CuO-Cu2O complex thin film can be used as an alternative hole transport layer (HTL) in industrially produced perovskite solar cells.

We have synthesized and characterized three perylene diimides, X-PDI, where X = H, F, or Br. These three compounds have been tested for the substitution of [6,6]-phenyl C₆₁ butyric acid methyl ester (PC₆₁BM) in inverted perovskite solar cells (PVSCs). Although the efficiency of PDI derivative-based conventional PVSCs is as high as 17.6% (J. Mater. Chem. A, 2016, 4, 8724), the corresponding performance of inverted PVSCs is still lagging behind and improvement is necessary. For electron accepting (from CH₃NH₃PbI₃ perovskite) and electron transporting properties of the materials, UV-visible absorption spectroscopy, electrochemical cyclic voltammetry, direct current conductivity, space-charge limited current (SCLC) electron mobility, atomic force microscopy (AFM) surface morphology, and photoluminescence (PL) spectroscopy gauging charge-trapping have been studied. The HOMO/LUMO energy levels are 5.94/4.00, 5.83/3.96, 6.00/3.97, and 5.48/3.73 eV for H-PDI, F-PDI, Br-PDI, and PC₆₁BM, respectively. Direct current conductivities of H-PDI, F-PDI, Br-PDI, and PC₆₁BM are 8.71 × 10⁻⁸, 1.18 × 10⁻⁹, 2.2 × 10⁻⁶, and 8.42 × 10⁻⁶ S cm⁻¹, respectively. The SCLC electron mobility of H-PDI, F-PDI, Br-PDI, and PC₆₁BM are 1.12 × 10⁻⁴, 8.31 × 10⁻⁶, 1.08 × 10⁻³, and 5.00 × 10⁻³ S cm⁻¹, respectively. PL spectroscopy of CH₃NH₃PbI₃ perovskite provides emission at wavelength of 781 nm, which is the same as for the perovskite layer covered with a thin film of H-PDI or F-PDI. However, the emission wavelength was blue-shifted to 773–774 nm when the perovskite layer was covered with a thin film of Br-PDI or PC₆₁BM. Using UV-visible absorption spectroscopy, the solubility (in chloroform) was determined as 1.2 × 10⁻², 8.7 × 10⁻² and >10⁻¹ mol L⁻¹ for F-PDI, H-PDI, and Br-PDI, respectively. In thin film state, UV-visible absorption spectroscopy indicated that the extent of molecular aggregation was F-PDI ≫ H-PDI > Br-PDI, which is consistent with the AFM-estimated root-mean-square roughness of F-PDI > H-PDI > Br-PDI ∼ PC₆₁BM. Without the solution processed ZnO NP cathode buffer layer (CBL), the power conversion efficiency (PCE) of H-PDI, F-PDI, Br-PDI, and PC₆₁BM PVSCs is ∼1%, ∼0%, 3.2%, and 4.1%, respectively. With the ZnO NP CBL, PCE is ∼7.8%, ∼0%, 10.5%, and 11.1% for H-PDI, F-PDI, Br-PDI, and PC₆₁BM PVSCs, respectively. Through this study, we have demonstrated that the simple mono-bromine substituted perylene diimide (Br-PDI), is solution processable and has potential for use as a non-fullerene electron accepting and electron transporting material in inverted PVSCs.

A new series of 9,10-diphenylanthracene (DPA)-based blue fluorophores have been synthesized and characterized for organic light-emitting diode (OLED) applications. These fluorophores have a bulky substituent, such as triphenylsilane in TPSDPA and mesitylene in TMPDPA, on the C-2 position. The C-2 substituent also includes electron transporting diphenylphosphine oxide in PPODPA and dimesitylene borane in BMTDPA, or hole transporting N-phenylnaphthalen-1-amine in NPADPA. For TMPDPA blue fluorophores, 9,10-diphenyl substituents of the anthracene core are further attached to hole-transporting 9H-carbazole in CBZDPA and electron-transporting 2-phenyl-1,3,4-oxadiazole in OXDDPA. Absorption and emission spectroscopic properties of all DPA-derived fluorophores, either in solution or in the condensed phase, were fully characterized and the HOMO/LUMO energy levels of these fluorophores were determined. The frontier molecular orbitals of the DPA derivatives were analysed by theoretical methods to determine the possible intramolecular charge transfer (ICT) characteristics. Whereas the blue emission is best preserved in TMPDPA, in which the non-conjugated bulky mesitylene group suppresses red-shifted emissions, the ICT is attributed to the deterioration in the emissions of NPADPA and BMTDPA. In the solid state, PPODPA suffered from red-shifted and weakened emissions because of adverse crystallization, which is promoted by the dipolar nature of the diphenylphosphine oxide substituent. Non-dopant OLEDs were fabricated with DPA, TPSDPA, TMPDPA, PPODPA, CBZDPA, and OXDDPA. Except for PPODPA, the electroluminescence efficiency of these DPA derivatives was significantly improved compared with that of the DPA OLEDs. In particular, CBZDPA and OXDDPA OLEDs exhibited the best external quantum efficiency of 4.5% and 4.0% with a true blue colour, with CIE_x,y coordinates of (0.17, 0.17) and (0.16, 0.18), respectively. The improved electroluminescence efficiency can be attributed to the molecular charge transport design of CBZDPA and OXDDPA.