Whispering Gallery Mode Assisted Enhancement in the Power Conversion Efficiency of DSSC and QDSSC Devices Using TiO₂ Microsphere Photoanodes

Abstract

Mesoporous TiO2 nanoparticles are excellent photoanodes for sensitized solar cells (SSC). However, a significant loss in the photoconversion efficiency (PCE) occurs due to the inefficient light absorption. Large Mie scattering from mesoporous micron-sized spheres could be used to enhance the absorption and hence the PCE. Here, we show that a composite comprising a TiO2 mesoporous microsphere with smooth surface (SμS-TiO2) exhibiting whispering gallery modes (WGM) and a commercial TiO2 mesoporous nanoparticle (Degussa P25) with an optimum ratio (80:20 wt %) shows significant enhancement in PCE of DSSC and QDSSC devices. SμS-TiO2 exhibits strong WGM as evidenced from the photoluminescence studies carried out using a laser with an excitation wavelength λexc = 325 nm. These microspheres sensitized with N719 dye or CdSe/CuInS2 QDs are shown to exhibit emission characteristics strongly coupled to WGM resulting in an enhanced PCE in SSC. Increases in PCE of ∼24% in DSSC devices and 80–95% in QDSSC devices of 0.25 cm2 area are demonstrated. Thus, TiO2 composite exhibiting WGM can be used as a generic photoanode to achieve maximum PCE for Grätzel type sensitized solar cells. This study suggests special class of solar cells called “whisperonic solar cells”.

Quantum Dot Sensitized Whisperonic Solar Cells—Improving Efficiency Through Whispering Gallery Modes

“…Later, it was shown that a significant increase in efficiency, in fact, arises from the increased absorption by the dye, mainly modulated by the WGM arising from the microspheres (Das et al, 2018a). Similar enhancement was shown to prevail in QDSSC and semiconductor sensitized solar cell (SCSSC) devices (Das et al, 2018a;Ilaiyaraja et al, 2019). Extensive studies carried out by fabricating QDSSC devices using CdSe QDs and CuInS 2 QDs are reported (Das et al, 2018a;Ilaiyaraja et al, 2018).…”

“…The composite structure proposed by Ilaiyaraja et al possesses properties of high light scattering, higher surface area, and low interfacial resistance, which are desired for efficient electron generation and transport (Ilaiyaraja et al, 2017). Later, it was shown that a significant increase in efficiency, in fact, arises from the increased absorption by the dye, mainly modulated by the WGM arising from the microspheres (Das et al, 2018a). Similar enhancement was shown to prevail in QDSSC and semiconductor sensitized solar cell (SCSSC) devices (Das et al, 2018a;Ilaiyaraja et al, 2019).…”

“…Few other strategies are being investigated for bettering the performance of cells. These include surface passivation (Zhao et al, 2012), molecular linker assistance (Pernik et al, 2011), device architecture (Zhu et al, 2013), light trapping for enhanced absorption (Kim and Yong, 2013), adopting whispering gallery resonators in the photoanode (Das et al, 2018a), etc.…”

“…One notable version is the plasmonic solar cell (Catchpole and Polman, 2008). Another concept recently gaining momentum is the use of whispering gallery modes (WGMs) to effectively scatter the light (Grandidier et al, 2011;Das et al, 2018a;Wang et al, 2018a). The latter has led to a new type of solar cell broadly classified as "whisperonic solar cell" (Das et al, 2018a).…”

“…Another concept recently gaining momentum is the use of whispering gallery modes (WGMs) to effectively scatter the light (Grandidier et al, 2011;Das et al, 2018a;Wang et al, 2018a). The latter has led to a new type of solar cell broadly classified as "whisperonic solar cell" (Das et al, 2018a). The photoanode in these devices is modified so as to exhibit optical whispering gallery resonances while it exhibits the rest of all the characteristics required for the functioning of SSCs.…”