Confocal spectrometer for study of organic-inorganic perovskites

Abstract

Organic-inorganic perovskites (OIPs) are promising photovoltaic materials due to the simplicity of synthesis technique and attractive physical properties. It is known that the power conversion efficiency of solar cells with an OIP photoabsorbing layer has recently reached approximately 23%. Unfortunately, OIPs easily degrade under influence of heat, moisture, oxygen and light soaking. Encapsulation of OIP layers to protect them against moisture and oxygen is necessary, which hampers to use traditional methods of analysis such as electron and probe microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, X-ray diffraction, etc. As a result, significant difficulties in determination of photodegradation mechanisms arise, so, we are forced to look for other techniques of highly informative nondestructive analysis of such structures. For studying photoinduced processes in OIP layers, we applied confocal spectrometer, which allowed to use a laser beam (i) as a source of optical radiation causing photodegradation; (ii) for the local analysis of changes in the structure of the area exposed to optical radiation using Raman and photoluminescence (PL) spectra; (iii) for local measurement of solar cell parameters (short circuit current, open circuit voltage). The presence of a 3D piezoelectric scanner enables one to do the mapping of spectral and photoelectric parameters, which is important for establishing the homogeneity of the objects under study. The proposed approach allows obtaining information on the phase composition and spectrum of electronic states (from the Raman and PL spectra), as well as on the dynamics of charge carriers. By recording PL and Raman spectra, short circuit current and open circuit voltage under laser beam illumination, one can observe the evolution of the system in th