As
single-junction Si solar cells approach their practical efficiency
limits, a new pathway is necessary to increase efficiency in order
to realize more cost-effective photovoltaics. Integrating III–V
cells onto Si in a multijunction architecture is a promising approach
that can achieve high efficiency while leveraging the infrastructure
already in place for Si and III–V technology. In this Letter,
we demonstrate a record 15.3%-efficient 1.7 eV GaAsP top cell on GaP/Si,
enabled by recent advances in material quality in conjunction with
an improved device design and a high-performance antireflection coating.
We further present a separate Si bottom cell with a 1.7 eV GaAsP optical
filter to absorb most of the visible light with an efficiency of 6.3%,
showing the feasibility of monolithic III–V/Si tandems with
>20% efficiency. Through spectral efficiency analysis, we compare
our results to previously published GaAsP and Si devices, projecting
tandem GaAsP/Si efficiencies of up to 25.6% based on current state-of-the-art
individual subcells. With the aid of modeling, we further illustrate
a realistic path toward 30% GaAsP/Si tandems for high-efficiency,
monolithically integrated photovoltaics.
Visible light communication systems can be used in a wide variety of applications, from driving to home automation. The use of wearables can increase the potential applications in indoor systems to send and receive specific and customized information. We have designed and developed a fully organic and flexible Visible Light Communication system using a flexible OLED, a flexible P3HT:PCBM-based organic photodiode (OPD) and flexible PCBs for the emitter and receiver conditioning circuits. We have fabricated and characterized the I-V curve, modulation response and impedance of the flexible OPD. As emitter we have used a commercial flexible organic luminaire with dimensions 99 × 99 × 0.88 mm, and we have characterized its modulation response. All the devices show frequency responses that allow operation over 40 kHz, thus enabling the transmission of high quality audio. Finally, we integrated the emitter and receiver components and its electronic drivers, to build an all-organic flexible VLC system capable of transmitting an audio file in real-time, as a proof of concept of the indoor capabilities of such a system.
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