Doping distribution of an operating organic light-emitting diode: a raman map analysis

We present confocal Raman spectroscopy (CSRS) maps of Poly(9,9-dioctylfluorene) (PFO)-based organic light emitting diode under operation. The CSRS analysis of the OLEDs was performed in normal room conditions. The non-emissive spots presented higher Raman intensity and broadening of the vibrational bands in comparison with the luminescent ones. The phenomenon is associated with an increase in the PFO - * absorption band and hence modification of the PFO doping which becomes favorable to the excitation wavelength, thus the Raman spectrum is enhanced. To the authors’ knowledge this image technique had been missed for the OLED technology

Solar cell parameter accuracy improvement, via refinement of the Co-Content function:Part 1: Theoretical analysis

In this Part 1 of this series of articles, the accuracy on the obtention of the shunt resistance (R sh), the series resistance (R s), the ideality factor (n), the light current (I lig), and the saturation current (I sat), via the use of the Co-content function CCV,I= ∫ 0VI-IscdV (where Isc=IV=0 ) is investigated theoretically, as function of the number of measured points per voltage ( PV ) and percentage noise ( pn ). Reasonable values are obtained for R sh, R s, and I lig, with PV = 11 measurement points per V if the pn is 0.1% or less. For a reasonable determination of n at least PV = 101 measurement points per V are needed. I sat determination requires pn of 0.01% or lower with at least PV = 101 measured points per V and should be evaluated at large values of V. The results given in this Part 1 are used in Part 2 to discuss the reported application of the CCV,I to obtain R sh, R s, n, I lig, and I sat found in the literature

Solar cell parameter accuracy improvement, via refinement of the Co-Content function:Part 2: Discussion on the experimental application

In this Part 2 of this series of articles, a discussion of the literature reported obtention of the solar cell parameters (the shunt resistance (R sh ), the series resistance (R s ), the ideality factor (n), the light current (I lig ), and the saturation current (I sat )), via the use of the Co-content function CCV,I= ∫0VI-IscdV (where Isc=I(V=0) ) is given. The results reported in Part 1, namely, the accuracy dependence of the determination of R sh , R s , n, I lig , and I sat , as a function of the number of measured points per voltage ( PV ) and percentage noise ( pn ) is used to analyse the reported solar cell parameters. In one case, the application of CCV,I to solar panels is discussed, revealing that it can also be used in the case of solar panels, and not only for laboratory-made solar cells, in voltage ranges larger than [0 V, 1 V]. In another case, the application of CCV,I to IV curves showing the roll-over effect is discussed. It is found that the roll-over effect has a pernicious effect in the solar parameter extraction, and then the CCV,I should be calculated before the roll-over effect takes place. In a third case, the importance of the correct determination of Isc on the correct calculation of CCV,I is discussed

Deep levels in GaInNAs grown by molecular beam epitaxy and their concentration reduction with annealing treatment

Deep-level transient Fourier spectroscopy (DLTFS) technique is used to investigate the thermal-annealing behaviour of at least five deep levels in two samples of Ga0.987In0.013N0.0043As0.9957, one medium doped with Si (2 × 1016 cm−3) and the second one heavily doped with Si (1 × 1018 cm−3) grown by molecular beam epitaxy (MBE). The thermal-annealing study was done at 650, 700, 750 and 800 °C for 5 min. One main electron trap with activation energy of 0.97 eV, a capture cross section of 5.5 × 10−11 cm2 and a density of 3.2 × 1014 cm−3 is detected for the medium-doped as-grown sample. For the heavily doped sample one main electron trap with activation energy of 0.35 eV, a capture cross section of 7.1 × 10−14 cm2 and a density of 2.2 × 1015 cm−3 is detected. For the heavily doped sample, this electron trap only decreases its density as the annealing temperature increases. No more deep centres appear with annealing. For the medium-doped sample, the main electron trap decreases its density as the annealing temperature increases, but unlike the heavily doped sample, four more deep centres appear, depending on the annealing temperature. Their annealing temperature dependence and possible origin of the electron traps are reported for the first time