Recent advancements in CdTe solar cell technology have introduced the integration of flexible substrates, providing lightweight and adaptable energy solutions for various applications. Some of the notable applications of flexible solar photovoltaic technology include building integrated photovoltaic systems (BIPV), transportation, aerospace, satellites, etc. However, despite this advancement, certain issues regarding metal and p-CdTe remained unresolved. Besides, the fabrication of a full-working device on flexible glass is challenging and requires special consideration due to the unstable morphology and structural properties of deposited film on ultra-thin glass substrates. The existing gap in knowledge about the vast potential of flexible CdTe solar cells on UTG substrates and their possible applications blocks their full capacity utilization. Hence, this comprehensive review paper exclusively concentrates on the obstacles associated with the implementation of CdTe solar cells on UTG substrates with a potential back surface field (BSF) layer. The significance of this study lies in its meticulous identification and analysis of the substantial challenges associated with integrating flexible CdTe onto UTG substrates and leveraging Cu-doped ZnTe as a potential BSF layer to enhance the performance of flexible CdTe solar cells.

In this study, Solar Cell Capacitance Simulator (SCAPS-1D) is utilized to examine the properties of cadmium telluride (CdTe) based solar cell. The key aim of this study is to explore the prospects of enhancing the efficiency of CdTe solar cells by adding a high resistivity transparent (HRT) layer to the conventional cell structure. For that purpose, novel HRT layer structures are suggested in CdTe solar cells between a cadmium sulfide (CdS) window layer and transparent conductive oxide (TCO) layer. Simulation results presented in this paper are from four proposed structures with three different HRT materials compared to the conventional design. The optimal parameters that offer the optimum functionality of the conventional design (SnO₂/CdS/CdTe/MoTe₂), with and without the HRT layer, are determined. Obtained results validate an enhancement in efficiency of the solar cell with Zn₂SO₄ as the HRT layer due to lower recombination loss and barrier height at the back contact region. The suggested cell with Zn₂SO₄ demonstrates an efficiency of 17.61% (Voc = 0.92 V, Jsc = 25.41 mA/cm², FF = 75.35), with only 20 nm HRT layer and 25 nm CdS as a window layer. In the meantime, the reference cell (no HRT layer) depicts an efficiency of 17.01% with 4000 nm thick CdTe as an absorber layer. However, the normalized efficiency of the suggested cells decreases linearly with increased temperature.