Suppression of Defects Through Cation Substitution: A Strategic Approach to Improve the Performance of Kesterite Cu₂ZnSn(S,Se)₄ Solar Cells Under Indoor Light Conditions

Abstract

Recent efficiency advancements in kesterites have reinforced the use of Cu2ZnSn(S,Se)4 (CZTSSe) in indoor photovoltaic applications. However, the performance of kesterites under low light intensity conditions is mainly hindered by deep‐level defects. In this study, a strategic approach of silver (Ag) and germanium (Ge) cation substitution to cure these defects are employed. The Ag‐doped CZTSSe (CZTSSe:Ag) and Ge‐doped (CZTSSe:Ge) samples experimentally demonstrated a significant improvement in kesterite device performance under all intensities of LED and white fluorescent lamp conditions are prepared. Interestingly, the CZTSSe:Ag device exhibited the highest performance levels, i.e., 1.2–1.5 and 2.5–3 times better than those of Ge‐doped CZTSSe:Ge and undoped CZTSSe, respectively. This improved device performance is mainly attributed to the reduced energy level of deep‐level defects in CZTSSe:Ag. Moreover, these defects assisted in the generation of a larger potential difference between the grain boundary and grain interior in the CZTSSe:Ag sample, attracting minority carriers near the grain boundary. Consequently, the improved carrier separation process reduced the carrier recombination losses and enhanced the power output under low light intensity conditions. This Ag and Ge cation substitution in kesterite is found to be an effective approach to improve the device performance under low light intensity conditions.

Effect of Self‐Seed Inducing on the Growth Mechanism and Photovoltaic Performance of Cu2ZnSnSe4 Thin Films

“…The Fermi level position of the 7-cycle sample markedly shifted toward the valence band, which indicates the existence of shallow level defects. This corresponds to the results determined by Park et al [54] The Fermi level position greatly shifted away from the valence band for the 1-cycle sample, which suggests that the Fermi level was fixed at deep levels owing to the existence of a deep level recombination center.…”

Engineering of Interface and Bulk Properties in Cu2ZnSn(S,Se)4 Thin-Film Solar Cells with Ultrathin CuAlO2 Intermediate Layer and Ge Doping

“…We calculated the average CPDs at the GBs and GIs as well as the difference between those at the GBs and GIs (CPD GI‑GB ) for both samples, as shown in Figure e. Notably, the absolute CPDs at GBs and GIs increased for the CAO/CZTSSe-Ge samples compared to the CZTSSe, which indicates that the sample surface work function is reduced due to the Ge doping . In addition, CPD GI‑GB is larger for the CAO/CZTSSe-Ge sample than for the CZTSSe sample.…”

“…The soft prealloying process and tailoring Mo surface cannot completely suppress Mo­(S,Se) 2 formation; to circumvent this issue, various intermediate layers such as Al 2 O 3 , ZnO, TiO 2 , TiB 2 , graphene oxide (GO), carbon, Ag, VSe 2 , MoO 3 , and CuO have been investigated to minimize the formation of Mo­(S,Se) 2 during the sulfo-selenization process. ,, The p-type transparent conducting oxide materials can effectively transport holes and minimize the electron transport in TFSCs . As a back-intermediate layer, CuAlO 2 (CAO) can be a suitable candidate because it has p-type electrical conductivity and consists of earth-abundant and nontoxic elements, as the CZTSSe materials. , In our previous study, we improved the device efficiency with an individual attempt of back-interface passivation with a CAO layer and defect passivation in CZTSSe through Ge doping. , However, the application of the back-interface passivation layer could not suppress the density of bulk defects to a larger extent. The metallic layer applied at the back-interface during a single cation substitution also does not prevent the interfacial reaction among S/Se vapors.…”

“…35,36 In our previous study, we improved the device efficiency with an individual attempt of back-interface passivation with a CAO layer and defect passivation in CZTSSe through Ge doping. 37,38 However, the application of the back-interface passivation layer could not suppress the density of bulk defects to a larger extent. The metallic layer applied at the back-interface during a single cation substitution also does not prevent the interfacial reaction among S/Se vapors.…”

Energy Solutions for Wearable Sensors: A Review

“…Solar cells need further optimization to enhance their indoor performance, as the weather is not controllable and users spend most of their time inside buildings. It is worth mentioning that presently, many studies have been devoted to improving the indoor performance of solar cells [ 44 , 45 ], known as indoor photovoltaics. One work studying a photovoltaic-thermoelectric hybrid energy generator aims at achieving satisfactory self-powering ability in indoor environments when used in wearable devices [ 46 ].…”