Oxygenated CdS Buffer Layers Enabling High Open‐Circuit Voltages in Earth‐Abundant Cu₂BaSnS₄ Thin‐Film Solar Cells

Abstract

Earth‐abundant Cu2BaSnS4 (CBTS) thin films exhibit a wide bandgap of 2.04–2.07 eV, a high absorption coefficient > 104 cm−1, and a p‐type conductivity, suitable as a top‐cell absorber in tandem solar cell devices. In this work, sputtered oxygenated CdS (CdS:O) buffer layers are demonstrated to create a good p–n diode with CBTS and enable high open‐circuit voltages of 0.9–1.1 V by minimizing interface recombination. The best power conversion efficiency of 2.03% is reached under AM 1.5G illumination based on the configuration of fluorine‐doped SnO2 (back contact)/CBTS/CdS:O/CdS/ZnO/aluminum‐doped ZnO (front contact).

Enhancement in the Efficiency of Sb2Se3 Thin‐Film Solar Cells by Increasing Carrier Concertation and Inducing Columnar Growth of the Grains

“…Thus, the energy level diagrams (Figure d) show that for oxygen plasma‐treated CdS, the CBM is upshifted, which means that the Fermi level is farther from the CBM. This increased distance can prevent the electrons from reaching the Fermi level, which reduces the effective interface recombination between the Sb 2 Se 3 and CdS . On the other hand, with the decrease in the surface roughness of the oxygen plasma‐treated CdS film, the Sb 2 Se 3 film can grow more uniformly and unidirectionally on CdS film; therefore, the contact between the CdS and Sb 2 Se 3 is improved, which will decrease the contact resistance.…”

Proposition of an Environment Friendly Triple Junction Solar Cell Based on Earth Abundant CBTSSe/CZTS/ACZTSe Materials

“…It has been experimentally shown that CBTSSe/FTO and CZTS/ITO interfaces are practically realizable. [19,20] Therefore, our proposed triple junction solar cell is experimentally viable with the existing fabrication technology.…”

“…As a result, current density falls significantly with the higher thickness of CZTS (Figure 2(a)) because of the reduced optical power absorption in the bottom cell. Thus, higher thickness of [19] 7 [18] 8.5 [17] 7 [16] Band gap (eV) 1.9 [14] 1.45 [18] 0.97 [17] 0.9 [16] Electron affinity (eV) 3.6 [19] 4.1 [24] 4.05 [17,25] 4.05 [13] Electron effective mass (m e /m o ) 0.37 [14,15] 0.18 [13,16] 0.08 [17] 0.07 [13,16] Hole effective mass (m p /m o ) 1.68 [14] 2 [13,16] 0.3 [17] 0.2 [13,16] Electron mobility (cm 2 V À1 s À1 ) 3 0 [26] 40 [21,24] 75 [23] 145 [13,21] Hole mobility (cm 2 V À1 s À1 ) 1 0 [27] 25 [21] 1 [17,23] 35 [13,21] Acceptor concentration (cm…”

“…In order to predict the minimum efficiency of our proposed structure, we have used much less minority carrier life times (0.25-0.52 ns) than that of the reported values in literature (7.1-11 ns). [18,19,23] The detailed simulation procedure and the other electrical and optical parameters along with their references can be found in the Supporting Information.…”

“…Lumerical and Matlab software packages were used for solving these equations. The optical parameters of the absorbers are taken from literature [19,21,22] and Table 1 represents the electrical parameters of CBTSSe, CZTS, ACZTSe, CZTSe used in our simulation procedure. In order to predict the minimum efficiency of our proposed structure, we have used much less minority carrier life times (0.25-0.52 ns) than that of the reported values in literature (7.1-11 ns).…”