Direct Contact of Selective Charge Extraction Layers Enables High-Efficiency Molecular Photovoltaics

Abstract

Dye-sensitized solar cells (DSCs) are molecular photovoltaics that operate efficiently in direct solar and ambient light by employing dye-impregnated mesoscopic TiO2 films with a redox electrolyte or hole conductor. Here, we report on an advanced DSC architecture, which achieves efficiencies of 13.1% under air mass 1.5 global, 100 mW cm−2 solar radiation, and power conversion efficiency of 32% under a standard Osram 930 Warm White fluorescent tube light at 1,000 lux intensity. The cell substantially benefits from the direct contact of the dye-impregnated TiO2 film with the poly(3,4-ethylenedioxythiophene) (PEDOT) counter electrode acting as a hole collector. This reduces the diffusion path of redox mediator to merely the mesoporous TiO2 film attenuating the Warburg resistance, which thereby boosts the photovoltaic performance. This architecture will not only accelerate the practical exploitation of DSCs, but also foster new types of light-harvesting devices using mesoscopic TiO2 and PEDOT as electron and hole collection layers, respectively. The quality of life is quantified by the Human Development Index (HDI), varying between zero and one. A larger HDI indicates a higher quality of life and increased electricity consumption. The annual per capita electricity consumption is expected to be 55 MWh when the HDI increases to 0.9. The electricity demand would increase drastically if all humans aspired to attain such a high HDI value. Since electricity consumption includes substantial indoor lighting, the photovoltaic recycling it to electric power opens a route to save energy. Here we introduce a new generation of dye-sensitized solar cells (DSCs) that reaches record power conversion efficiency (PCE) of 32% under ambient light, exceeding the performance of today's best photovoltaics based on silicon or GaAs. Excellent photovoltaic performance under full sunlight reaches 13.1% PCE. The DSC is very promising for power electronic devices and Internet of Things-related appliances using both ambient and direct sunlight. Dye-sensitized solar cells (DSCs) are molecular photovoltaics that operate efficiently in direct solar and ambient light. The conventional DSC architecture separates the mesoscopic TiO2 film from the catalytic counter electrode (e.g., Pt) by a spacer. Here, we report on a DSC embodiment employing an advanced structure, where the mesoporous TiO2 electrode and the poly(3,4-ethylenedioxythiophene) counter electrode are directly contacted without using any spacer. This new generation of DSC achieves efficiencies of 13.1% under standard sunlight and 32% under ambient light.