Study and characterization of mixed cation perovskite solar cells

Author(s)

Larissa de Oliveira Garcia

• Document type: Master's Dissertation
• Press: Bauru. 2022-03-21.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências. Bauru
• Defense date: 2022-03-11
• Advisor: Carlos Frederico de Oliveira Graeff; Silvia Leticia Fernandes

Abstract

One of the main obstacles to large-scale application of perovskite solar cells (PSCs) is the stability of perovskite (PVK) materials in terms of crystal structure, stoichiometry and optoelectronic characteristics during prolonged and adverse operating conditions. The impacts caused by degradation have been significantly reduced by compositional engineering. However, there are remaining concerns due to physical and chemical factors of the devices involving ionic migration, presence of defects in the PVK structure and hysteresis behavior. During this dissertation, changes were made in the proportion of halides in a mixed cation PVK and different results regarding crystallization, reproducibility and optical properties of the material were obtained and discussed. Samples containing the highest concentration of bromides (17%) showed an efficiency improvement (PCE) reaching 16.95%, J sc = 21.69 mA.cm-2, Voc = 1.03 V and FF= 75.65 %. On the other hand, devices without bromides showed low reproducibility, increase in hysteresis index (0.28) and significant losses in photovoltaic parameters (J sc = 14.25 mA.cm-2 , Voc = 0.84 V, FF= 35.67 % and PCE = 5.22%). The influence of the substrate during the crystallization of PVK films was also studied and a decrease in grain size was observed according to the wettability of the PVK solution and the compact ETL of the device. Higher number of grains could be observed for samples prepared by spin coating (SC) which promoted an increase in hysteresis index (0.14) and a decrease in the photovoltaic parameters (J sc = 22.20 mA.cm-2, Voc = 1.02 V, FF= 69.12 % and PCE=15.68 %), when compared to the devices containing ETL deposited by Magnetron Sputtering (RS) (J sc = 22.04 mA.cm-2, Voc = 1.05 V, FF = 73.42 % and PCE = 17.00 %). In order to improve these results, a passivating layer of PMMA was applied to improving the electrical parameters of the CSPs based on ETL_SC (J sc = 22.60 mA.cm-2 , Voc=1.05 V, FF = 71.78 % and PCE = 17.04 %). Finally, the replacement of the gold metallic electrode by a carbon ink proved to be promising and devices with PCE = 8.52% were obtained. (AU)

• FAPESP's process: 20/04905-1 - Study of the influence of humidity on mixed cation perovskites applied to photovoltaic devices
• Grantee: Larissa de Oliveira Garcia
• Support Opportunities: Scholarships in Brazil - Master