Trap Assisted Transition Energy Levels of SrF2:Pr3+-Yb3+ Nanophosphor in TiO2 Photoanode for Luminescence Tuning in Dye-Sensitized Photovoltaic Cells

Abstract

Luminescent nanophosphors as spectral converters offer immense potential for dye-sensitized photovoltaics (DSPV) to harvest wide range of solar spectrum. Herein, we demonstrate a novel structural design of DSPV by employing downconverting ( dc ) nanophosphor layer in TiO2 photoanode for indoor (ambient) applications. Cubic SrF2:Pr3+-Yb3+ nanoparticles are synthesized by template-free hydrothermal technique. The dc nanophosphor absorbs photons of blue region leading to emission of broad luminescence band (green and red), which is well-matched with N719-dye absorption. For the first time, we have designed a unique Pr3+-Yb3+ co-doped dc system yielding tuned and intensified luminescence by effective cross-relaxation (CR) with back energy transfer (BET) mechanism and demonstrated efficient working of the dc nanophosphor layered DSPVs under indoor LED light (Warm-3200K; Day-5000K) conditions. The dc-DSPV achieved high PCE of 14.85 and 15.9% respectively under indoor low light conditions (1000 lux). This approach resulted in 63.44% increment in output power density for dc-DSPV compared with control-DSPV under LED-3200K irradiation. These findings suggested that this configuration of dc -layered DSPV can provide new strategy for future indoor electronic-operations under ambient light conditions. Keywords: DSPV, downconversion, SrF2:Pr3+-Yb3+, luminescence tuning, trap assisted transition energy levels, interfacial charge transport kinetics and indoor light condition. Acknowledgement: This work was supported by Brain Pool Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT, Korea. (Grant number: 2019H1D3A1A01071183). It was also supported by the Technology Development Program to Solve Climate Changes of the National Research Foundation, funded by the Ministry of Science, ICT & Future Planning (No: NRF-2016M1A2A2940912). Figure 1