Citation: Hosen, A.; Rahman, S.; Brella, M.; Ahmed, S.R.A. Impact of Hole Transport Layers in Inorganic Lead-Free B-γ-CsSnI 3 Perovskite Solar Cells: A Numerical Analysis. Eng. Proc. 2022, 19, 41. https:// doi.org/10.3390/ECP2022-12611 Academic Editor: Maela Manzoli Published: 17 May 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Proceeding Paper Impact of Hole Transport Layers in Inorganic Lead-Free B-γ-CsSnI 3 Perovskite Solar Cells: A Numerical Analysis † Adnan Hosen 1, * , Sabrina Rahman 1 , Maroua Brella 2 and Sheikh Rashel Al Ahmed 1, * 1 Department of Electrical, Electronic and Communication Engineering, Pabna University of Science and Technology, Pabna 6600, Bangladesh; srmithila@gmail.com 2 Laboratoire de Rayonnement et Plasmas et Physique des Surfaces (LRPPS), Université Kasdi Merbah, Ouargla 30000, Algeria; brellamar@gmail.com * Correspondence: adnan_hosen@yahoo.com (A.H.); rashel@pust.ac.bd (S.R.A.A.) † Presented at the 1st International Electronic Conference on Processes: Processes System Innovation, 17–31 May 2022; Available online: https://sciforum.net/event/ECP2022. Abstract: Tin-based halide perovskite compounds have attracted enormous interest as effective replacements for the conventional lead halide perovskite solar cells (PCSs). However, achieving high efficiency for tin-based perovskite solar cells is still challenging. Herein, we introduced copper sulfide (CuS) as a hole transport material (HTM) in lead free tin-based B-γ-CsSnI 3 PSCs to enhance the photovoltaic (PV) performances. The lead free tin-based CsSnI 3 perovskite solar cell structure consisting of CuS/CsSnI 3 /TiO 2 /ITO was modeled and the output characteristics were investigated by using the one dimensional solar cell capacitance simulator (SCAPS-1D). The CuS hole transport layer (HTL) with proper band arrangement may notably minimize the recombination of the charge carrier at the back side of the perovskite absorber. Density functional theory (DFT)-extracted physical parameters including the band gap and absorption spectrum of CuS were used in the SCAPS-1D program to analyze the characteristics of the proposed PV device. The PV performance parameters of the proposed device were numerically evaluated by varying the absorber thickness and doping concentration. In this work, the variation of the functional temperature on the cell outputs was also studied. Furthermore, different HTMs were employed to investigate the PV characteristics of the proposed CsSnI 3 PSC. The power conversion efficiency (PCE) of ~29% was achieved with open circuit voltage (V oc ) of 0.99 V, a fill factor of ~87%, and short circuit current density (J sc ) of 33.5 mA/cm 2 for the optimized device. This work addressed guidelines and introduced a convenient approach to design and fabricate highly efficient, inexpensive, and stable lead free tin-based perovskite solar cells. Keywords: perovskite; B-γ-CsSnI 3 ; HTL; CuS; DFT; SCAPS-1D 1. Introduction PSCs have attracted great attention as promising PV technologies due to their ad- mirable properties associated with excellent PCE and low fabrication cost. This new class of PV technology has recently received enormous interest owing to the emerging conversion efficiency of ~25% [1,2]. However, the rapid growth and commercialization of PSCs are impeded because of toxicity present in most commonly developed lead-based perovskite solar cells [3]. In this context, various attempts have been made in pursuit of suitable alternative for the lead-based perovskites [4–6]. Among different perovskite materials, the inorganic cesium tin triiodide (CsSnI 3 ) may be considered as one of the potential can- didates [7]. CsSnI 3 exhibits suitable optoelectronic properties including an ideal energy gap of ~1.3 eV, absorption coefficient (10 4 cm −1 ), high charge-carrier mobilities (above 500 cm 2 V −1 s −1 ) and low exciton binding energy (~18 meV) [7,8]. In the previous work, an efficiency of 0.9% was reported with the architecture of indium tin oxide/CsSnI 3 /Au/Ti in 2012 [9]. An earlier work evaluated a maximum power conversion efficiency (PCE) of Eng. Proc. 2022, 19, 41. https://doi.org/10.3390/ECP2022-12611 https://www.mdpi.com/journal/engproc