UV-Selective Transparent PV Devices with Wide Bandgap ZnO_1-xS_x Mixed Crystal Absorbers Deposited by Atomic Layer Deposition for Seamless PV Building Integration

One of the great limitations of integrating PV technologies on window or ceramic façades is the high light absorption of existing technologies that give these devices an opaque appearance, and other issues as weight. Therefore, when applied on glass, ceramic, or polymeric substrates they completely modify their aesthetic properties, making them practically inapplicable to the vast majority of urban buildings where aesthetic value is of fundamental importance.^[1] This is a challenge since one of the most important aspects of non-intrusive integration of PV technologies is achieving a good balance between the efficiency of the cell and the degree of transparency. In this aspect, results have shown that wide-bandgap (WBG) materials based on oxides such as ZnO or ZnO_1-XS_X, present reasonably good photovoltaic properties while maintaining a high degree of transparency.^[2–4] Particularly, ZnO_1-XS_X has been proposed as an ideal UV absorber thanks to a composition-tuneable bandgap that can shift from 3.2 eV down to 2.7 eV at intermediate relative sulfur content, matching the UV spectral onset for the AM1.5G spectrum.^[5,6]<br/>In this work, transparent PV cells based on ZnO_1-XS_X with a relative sulfur content of x=0.7 and the architecture SLG/FTO/MoO₃(HTL)/ZnO_0.3S_0.7/ZnO/AZO(ETL)/AZO have been fabricated and characterized. Preliminary results present the first evidence of PV effect using a fully ALD-deposited ZnO_1-XS_X absorber and other WBG oxide materials as carrier selective contacts. These results show a notable V_oc of 401 mV but a low J_sc , limiting the PV effect. The Average Photopic Transmittance (APT) of the device has a value of 73%, showing indeed excellent transparency and color-neutrality thanks to the use of materials with bandgaps higher than 3eV. Optical, structural and electrical characterization of the absorber and devices will be presented (Spectrophotometry, Photothermal Deflection Spectroscopy, SEM, Raman, J-V characteristics under illumination). Ongoing work based on optoelectronic characterization will determine the UV detection capabilities of this structure measuring intensity dependent J-V characteristics under UV light under no bias as well as at the maximum-power-point, which are the prominent values at which a PV device will ideally operate. By such the TPV device based on this WBG material can be multifunctional and serve as a UV detector under PV operation. Also, to increase J_sc and thus PCE different compositions and selective contacts are being actively studied.<br/>This research is relevant for the advancement of thin film technologies and in particular Transparent PV technologies. The proposed architecture has the potential to revolutionize photovoltaic technology by enabling on-site generation while minimizing visual impact. It is noteworthy that ZnO_1-XS_X is a material composed of earth-abundant raw elements, compatible with scalable fabrication processes and can be synthesized at relatively low temperatures, which potentially allows minimizing the carbon footprint, the economic costs and energy expenditure associated with the manufacture of devices.<br/>This work has received funding from MCIN/AEI/10.13039/501100011033 under grant numbers PID2022-138434OB-C51 and TED2021-129758B-C32 and by the NextGeratiouEU/PRTR.<br/><br/>[1] C. J. Traverse, R. Pandey, M. C. Barr, R. R. Lunt, <i>Nat. Energy</i> <b>2017</b>, <i>2</i>, 849.<br/>[2] R. Karsthof, P. Räcke, H. Von Wenckstern, M. Grundmann, <i>Phys. status solidi</i> <b>2016</b>, <i>213</i>, 30.<br/>[3] M. Patel, H. S. Kim, J. Kim, J. H. Yun, S. J. Kim, E. H. Choi, H. H. Park, <i>Sol. Energy Mater. Sol. Cells</i> <b>2017</b>, <i>170</i>, 246.<br/>[4] R. Karsthof, H. von Wenckstern, M. Grundmann, <i>J. Vac. Sci. Technol. B, Nanotechnol. Microelectron. Mater. Process. Meas. Phenom.</i> <b>2016</b>, <i>34</i>, 04J107.<br/>[5] G. Baldissera, C. Persson, <i>J. Appl. Phys.</i> <b>2016</b>, <i>119</i>, DOI 10.1063/1.4940700.<br/>[6] A. J. Lopez-Garcia, A. Bauer, R. Fonoll Rubio, D. Payno, Z. Jehl Li-Kao, S. Kazim, D. Hariskos, V. Izquierdo-Roca, E. Saucedo, A. Pérez-Rodríguez, <i>Sol. RRL</i> <b>2020</b>, <i>4</i>, 2070112.