Incorporating Solution-Processed Mesoporous WO3 as an Interfacial Cathode Buffer Layer for Photovoltaic Applications

Abstract

Dextran templating hydrothermal synthesis of monoclinic WO3 exhibits excellent specific surface area of ~110 m2 /g and a mono-modal pore distribution with the average pore diameter of ~20 nm. Dextran plays a crucial role to generate porosity on WO3. The role of supporting dextran has been investigated and found to be crucial to tune the surface area, porosity and morphology. The photo-luminescence and X-ray photoelectron spectroscopy studies reveal about the existence of oxygen vacancies in sub-stoichiometric, which creates localized defect states of WO3 as synthesized through this templating method. The highly mesoporous WO3 have been further explored as an interfacial cathode buffer layer (CBL) in dye sensitized solar cells (DSSCs) and perovskite solar cells (PSCs). A significantly enhanced photo-conversion efficiency has been boosted up the performance of the counter electrode used in traditional DSSC (as platinum) and PSCs (as carbon) devices by ~48% and ~29%, respectively. The electrochemical impedance and the incident photon to current conversion efficiency (IPCE) studies were also analysed in order to understand the catalytic behaviour of the WO3 interfacial CBL for both DSSC and PSC, respectively. The much higher surface area of WO3 enables rapid electron hopping mechanism, which further benefits for higher electron mobility resulting in higher short circuit current. Through this study, we are able to unequivocally establish the importance of buffer layer incorporation, which can further help to integrate the DSSC and PSC devices towards more stable, reliable and enhanced efficiency generated device. In spite of that, using WO3 constitutes an important step towards the efficiency improvement of the devices for futuristic photo-electrochromic or selfpowered switchable glazing for low energy adaptive building integration.