Organic−inorganic hybrid perovskites have created significant opportunities for low-cost and high-performance solar cells. The electron transporting layer (ETL) is one of the main components of the solar cell, which selectively transports electrons and at the same time acts as a barrier for holes. This paper focuses on the ETL composed of titanium dioxide deposited by sol-gel method. In particular, perovskite solar cells with ETL from aged titanium sol revealed significant differences of short circuit current which is 8% higher than their counterpart with ETL from fresh sol. Analysis of ETL morphology by atomic force microscopy combined with electrochemical impedance spectroscopy and optical properties measurements enabled to determine the source of this diversity. Additionally, the role of roughness of transparent electrode was indicated. The in-depth material analysis revealed some disadvantages of the ETL material, originally considered as supporting higher photovoltaic performance. The results indicated several problems associated with hardly controlled aging conditions, defects and presence of residual water, strongly advocate for TiO2 ETL form the fresh sol, which after optimization can guarantee the same good solar cell performance.