Two-Dimensional Absorbers for Solar Windows: A Simulation

Abstract

In the future, many modern buildings may rely on solar windows for energy production. Large buildings often have glass facades that have the potential to convert sunlight to electrical power. The standard photovoltaic materials used today are bulky and not transparent, making them poor candidates for solar windows. Transition metal dichalcogenides (TMDCs) and other two-dimensional absorbers are a good alternative because of their unique properties and high transparency at the monolayer and few-layer regime. This work shows the potential for TMDC-based solar windows by simulating the transmission, quantum efficiency, current density, and colour appearance of different solar cell configurations. Different contacts were investigated, along with the influence of contact thickness, to demonstrate colour-neutral solar cells. In addition, four TMDC materials were compared: MoS2, MoSe2, WS2, and WSe2. Colour-neutral solar cells with transparencies of 35 % to 55 % are presented, where a current density of 8.33 mA/cm2 was calculated for a solar cell with a 5-nm absorbing layer of MoSe2. While there are still challenges to overcome in terms of production, our simulations show that it is possible to use TMDCs for colour-neutral solar windows and act as a guideline for further research.

Optoelectronic Properties of MoS2 in Proximity to Carrier Selective Metal Oxides

“…Therefore, these approaches could not benefit from the intrinsic properties of mono‐ and few‐layer MoS 2 , such as an increased band gap [ 12 ] and high absorption coefficient in thin layers, [ 13b ] and do not exploit the potential for transparent and semi‐transparent photovoltaic applications. [ 17 ]…”

“…Therefore, these approaches could not benefit from the intrinsic properties of mono-and few-layer MoS 2 , such as an increased band gap [12] and high absorption coefficient in thin layers, [13b] and do not exploit the potential for transparent and semi-transparent photovoltaic applications. [17] In order to take advantage of the unique mono-and few layer properties of MoS 2 as absorption layers in solar cells, the TMDC films need to be integrated in a device stack that can separate and extract charge carriers from the TMDC light absorbing layer. Charge separation can be realized with carrierselective contact materials, such as titanium oxide (TiO x ) acting as an electron selective contact [18] and molybdenum oxide (MoO x ) acting as a hole selective contact.…”

Switchable Photocurrent Generation in an Ultrathin Resonant Cavity Solar Cell

“…27−30 The cavity in our work is based on an a-Ge:H ultrathin solar cell, 31 with the main advantage to enable the integration of new absorber materials like transition metal dichalcogenides in switchable PV windows, as shown recently. 32 In this study, we demonstrate a switchable optical cavity with broadband enhanced absorption in a 5 nm thick a-Ge:H layer, with on demand photocurrent generation. This paves the way toward switchable photovoltaic windows, as recently introduced by our research group.…”

“…We create a switchable ultrathin resonant optical cavity by using thin gasochromic Mg/Pd layers as a switchable mirror behind an ultrathin static amorphous hydrogenated germanium (a-Ge:H) absorber layer. Instead of switching the optical properties of the absorber, the absorption enhancement of the cavity is switched by the change of optical properties of the Mg/Pd layer system. − The refractive index of Mg changes, when hydrogen is absorbed. − The cavity in our work is based on an a-Ge:H ultrathin solar cell, with the main advantage to enable the integration of new absorber materials like transition metal dichalcogenides in switchable PV windows, as shown recently . In this study, we demonstrate a switchable optical cavity with broadband enhanced absorption in a 5 nm thick a-Ge:H layer, with on demand photocurrent generation.…”

Ultrathin Nano-Absorbers in Photovoltaics: Prospects and Innovative Applications

“…Recently, following the old mindset "thinner is better" and also out of scientific curiosity, the following question arose: how thin can the absorber layer be using light confinement structures? It turns out that, again, it can be made 100 times thinner compared to mainstream thin film technology by using ultra-high α absorber materials in combination with very strong light confinement in an optical cavity [5][6][7].…”