The low-temperature colloidal solution processed tin oxide (SnO₂) based electron transport layer (ETL) has received impressive attention in the development of planar perovskite solar cells (PSC) to resolve issues encountered with conventional ETL, TiO₂, e.g. effect of elevated temperatures processing, low mobility, and UV photocatalytic activity. However, the presence of Sn vacancies and hydroxyl groups in SnO₂ hinders the PSC power conversion efficiency (PCE). To resolve these issues at the SnO₂ surface, post-processing of SnO₂ by using the KCl treatment has been proposed. To that end, doping of the SnO₂ ETL with trace amounts of NaCl, KCl, LiCl, and many other alkaline salts to reduce the vacancies inside the bulk layer have been explored. In this study, we have systemically studied the effect of undoped SnO₂ (M1), undoped KCl-treated SnO₂ (M2), and K-doped SnO₂ (M3) on the device performance. To the best of our knowledge, there is no study for systematical and simultaneous comparison between post-processing with KCl and pre-KCl inclusion inside the SnO₂ precursor on the device performance. Our optoelectronic and morphological investigations of these different SnO₂-based ETLs in the device reveal striking similarities as well as differences. Among the differences, the determined device diode quality factor (n_M1=1.73, n_M2=1.55, n_M3=1.51), reverse saturation current (smallest for M3 10^-7 mA/cm²), space charge limited current measurements (smaller trap filled voltage and defect density for M3) and contact angle measurements (higher wettability of perovskite ink on M3 surface). Transmittance spectroscopy (transmission exceedingly more than 75 % in the visible region in all three layer), surface roughness (~10 nm determined from atomic force microscopy (AFM), Scanning electron microscopy (SEM) (Figure 1(b)), and X-ray diffraction (XRD) reveals similar morphological features of differently processed M1, M2, M3 ETLs in the device fabrication. Further, steady-state photoluminescence (PL) quenching (Fig. 1(c) and time-resolved PL measurement of perovskite and ETL/perovskite also showed the improvement in case of M3 ETL. Moreover, upon the introduction of M1, M2, and M3 inside the device (Fig. 1(a, inset (b))), we observed better performance in M3-based ETL, corroborated by the device parameters from light J-V (Fig. 1(d)). This proves that doping the SnO₂ ETL not only provided better device performance, but also considerably reduces the process complexity for fabrication of perovskite solar cell.