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Article Citation - WoS: 18Citation - Scopus: 23Lead-Free Perovskite Homojunction-Based Htm-Free Perovskite Solar Cells: Theoretical and Experimental Viewpoints(Mdpi, 2023) Sajid, Sajid; Alzahmi, Salem; Salem, Imen Ben; Park, Jongee; Obaidat, Ihab M.Simplifying the design of lead-free perovskite solar cells (PSCs) has drawn a lot of interest due to their low manufacturing cost and relative non-toxic nature. Focus has been placed mostly on reducing the toxic lead element and eliminating the requirement for expensive hole transport materials (HTMs). However, in terms of power conversion efficiency (PCE), the PSCs using all charge transport materials surpass the environmentally beneficial HTM-free PSCs. The low PCEs of the lead-free HTM-free PSCs could be linked to poorer hole transport and extraction as well as lower light harvesting. In this context, a lead-free perovskite homojunction-based HTM-free PSC was investigated, and the performance was then assessed using a Solar Cell Capacitance Simulator (SCAPS). A two-step method was employed to fabricate lead-free perovskite homojunction-based HTM-free PSCs in order to validate the simulation results. The simulation results show that high hole mobility and a narrow band gap of cesium tin iodide (CsSnI3) boosted the hole collection and absorption spectrum, respectively. Additionally, the homojunction's built-in electric field, which was identified using SCAPS simulations, promoted the directed transport of the photo-induced charges, lowering carrier recombination losses. Homojunction-based HTM-free PSCs having a CsSnI3 layer with a thickness of 100 nm, defect density of 10(15) cm(-3), and interface defect density of 10(18) cm(-3) were found to be capable of delivering high PCEs under a working temperature of 300 K. When compared to formamidinium tin iodide (FASnI(3))-based devices, the open-circuit voltage (V-oc), short-circuit density (J(sc)), fill factor (FF), and PCE of FASnI(3)/CsSnI3 homojunction-based HTM-free PSCs were all improved from 0.66 to 0.78 V, 26.07 to 27.65 mA cm(-2), 76.37 to 79.74%, and 14.62 to 19.03%, respectively. In comparison to a FASnI(3)-based device (PCE = 8.94%), an experimentally fabricated device using homojunction of FASnI(3)/CsSnI3 performs better with V-oc of 0.84 V, J(sc) of 22.06 mA cm(-2), FF of 63.50%, and PCE of 11.77%. Moreover, FASnI(3)/CsSnI3-based PSC is more stable over time than its FASnI(3)-based counterpart, preserving 89% of its initial PCE. These findings provide promising guidelines for developing highly efficient and environmentally friendly HTM-free PSCs based on perovskite homojunction.Article Citation - WoS: 5Citation - Scopus: 5Diethanolamine Modified Perovskite-Substrate Interface for Realizing Efficient Esl-Free Pscs(Mdpi, 2023) Sajid, Sajid; Alzahmi, Salem; Wei, Dong; Ben Salem, Imen; Park, Jongee; Obaidat, Ihab M.Simplifying device layout, particularly avoiding the complex fabrication steps and multiple high-temperature treatment requirements for electron-selective layers (ESLs) have made ESL-free perovskite solar cells (PSCs) attractive. However, the poor perovskite/substrate interface and inadequate quality of solution-processed perovskite thin films induce inefficient interfacial-charge extraction, limiting the power conversion efficiency (PCEs) of ESL-free PSCs. A highly compact and homogenous perovskite thin film with large grains was formed here by inserting an interfacial monolayer of diethanolamine (DEA) molecules between the perovskite and ITO substrate. In addition, the DEA created a favorable dipole layer at the interface of perovskite and ITO substrate by molecular adsorption, which suppressed charge recombination. Comparatively, PSCs based on DEA-treated ITO substrates delivered PCEs of up to 20.77%, one of the highest among ESL-free PSCs. Additionally, this technique successfully elongates the lifespan of ESL-free PSCs as 80% of the initial PCE was maintained after 550 h under AM 1.5 G irradiation at ambient temperature.