CH 3 NH 3 PbI 3 layers chemically stabilized with poly(methyl methacrylate) (PMMA), relevant for photovoltaic applications, have been investigated by modulated surface photovoltage (SPV) spectroscopy at temperatures (T) between −182 and 60 °C. SPV is sensitive only to the PMMA/CH 3 NH 3 PbI 3 interface region where photogeneration and charge separation take place. The T dependencies of the Tauc gap (E g-Tauc , equivalent to absorption measurements) and of the gap determined from the maximum slope (E g-tp , almost at increased absorption) were analyzed on the basis of the in-phase SPV spectra. At 32 °C, the values of E g-Tauc and E g-tp were 1.540 and 1.560 eV, respectively. A jump of E g-Tauc and E g-tp by 10 meV at 40 °C was interpreted as the transition from the tetragonal to the cubic phase at T lower than values known from literature. E g-Tauc and E g-tp of the cubic phase decreased with increasing T. In contrast, E g-Tauc and E g-tp of the tetragonal phase decreased moderately with decreasing T to 1.528 and 1.546 eV at −182 °C, respectively. No signature has been observed in E g-Tauc and E g-tp for the transition from the tetragonal to the orthorhombic phase. Structural interactions at PMMA/CH 3 NH 3 PbI 3 interfaces seem important for phase transitions in CH 3 NH 3 PbI 3 layers.

A precipitation of CH 3 NH 3 PbCl 3 (MAPbCl 3 ) in CH 3 NH 3 PbI 3 (MAPbI 3 ) has been observed for deposition from solutions containing CH 3 NH 3 I (MAI), PbCl 2 and small amounts of ammoniumvaleric acid iodide (HOOC-(CH 2 ) 4 NH 3 I or AVAI) in N,N-dimethylformamide. The influence of the precipitation of MAPbCl 3 on the electronic properties of the free perovskite layer and of the nanoporous TiO 2 /perovskite nanocomposite has been investigated by modulated surface photovoltage spectroscopy. The lowest characteristic energy of exponentially distributed defect states below the band gap was found for the highest amount of AVAI in the solution (2.6% for the given experiments). Stabilization of MACl by AVA and the role of coadsorption of ions on TiO 2 surfaces for charge separation and layer formation are discussed on the basis of interaction and adsorption energies obtained by molecular modeling.

A sensitive electrochemical MIP sensor for salbutamol detection based on a graphene nanocomposite modified screen-printed carbon electrode was successfully demonstrated. Insertion of the graphene/ PEDOT:PSS layer prior to the MIP was aimed at enhancing the sensitivity of the sensor. Selection of a functional monomer was carried out using 1 H-NMR titration and a computational calculation was used to further investigate the template-monomer interactions. The MIP layer was constructed on top of the highly conductive nanocomposite by co-electropolymerization of 3-aminophenylboronic acid and o-phenylenediamine in the presence of salbutamol. Using differential pulse voltammetry under optimal conditions, a linear response in the range of 1 nM to 1.2 mM, with an exceptional detection limit of 100 pM (S/N ¼ 3) was obtained. The established sensor exhibited good reproducibility, reusability and stability. Additionally, good selectivity in discriminating salbutamol from other structurally related compounds could also be realized. Determination of salbutamol in real swine meat and feed samples was also successfully carried out with good recovery results.

Modulated surface photovoltage (SPV) spectra have been correlated with the phase composition in layers of CH3NH3PbI3 (MAPbI3) prepared from MAI and PbCl2 and annealed at 100 °C. Depending on the annealing time, different compositions of MAPbI3, MAPbCl3, MACl, PbI2, and an un-identified phase were found. It has been demonstrated that evaporation of MAI and HI is crucial for the development of electronic states in MAPbI3 and that only the appearance and evolution of the phase PbI2 has an influence on electronic states in MAPbI3. With ongoing annealing, (i) a transition from p- to n-type doping was observed with the appearance of PbI2, (ii) shallow acceptor states were distinguished and disappeared in n-type doped MAPbI3, and (iii) a minimum of the SPV response related to deep defect states was found at the transition from p- to n-type doping. The results are discussed with respect to the further development of highly efficient and stable MAPbI3 absorbers for solar cells.