Indoor utilization of emerging photovoltaics is promising; however, efficiency characterization under room lighting is challenging. We report the first round-robin interlaboratory study of performance measurement for dye-sensitized photovoltaics (cells and mini-modules) and one silicon solar cell under a fluorescent dim light. Among 15 research groups, the relative deviation in power conversion efficiency (PCE) of the samples reaches an unprecedented 152%. On the basis of the comprehensive results, the gap between photometry and radiometry measurements and the response of devices to the dim illumination are identified as critical obstacles to the correct PCE. Therefore, we use an illuminometer as a prime standard with a spectroradiometer to quantify the intensity of indoor lighting and adopt the reverse-biased current-voltage (I-V) characteristics as an indicator to qualify the I-V sampling time for dye-sensitized photovoltaics. The recommendations can brighten the prospects of emerging photovoltaics for indoor applications.

No abstract

A p-a-SiC:H window layer was used in amorphous Si thin film solar cells to boost the conversion efficiency in an indoor lighting of 500 lx. The p-a-SiC:H window layer/p-a-Si:H buffer layer scheme moderates the abrupt band bending across the p/i interface for the enhancement of VOC, JSC and FF in the solar spectra of short wavelengths. The optimized thickness of i-a-Si:H absorber layer is 400 nm to achieve the conversion efficiency of ~9.58% in an AM1.5 G solar spectrum. However, the optimized thickness of the absorber layer can be changed from 400 to 600 nm in the indoor lighting of 500 lx, exhibiting the maximum output power of 25.56 μW/cm2. Furthermore, various durability tests with excellent performance were investigated, which are significantly beneficial to harvest the indoor lights for applications in the self-powered internet of thing (IoT).

A p-type polycrystalline Ge (poly-Ge) film processed by UV and CO2 laser annealing reduces the hole concentration from 6 × 1018 to 2 × 1016 cm−3, accompanied by poly-grain growth. The decrease in hole concentration arises from the defect annealing using a CO2 laser, as demonstrated by the changes in the work function, that is, the valence-band maximum (VBM). The laser processes reduce the thermal budget for the fabrication of an enhancement-mode poly-Ge nMOSFET, which has a Ion/Ioff ratio of 5 × 103, a Vth of 2 V, and a subthreshold swing of 250 mV/dec., and will be potential fabrication methods for monolithic 3D integrated circuits in the future.

A low-thermal-budget n-type polycrystalline Ge (poly-Ge) channel that was prepared by plasma in-situ-doped nanocrystalline Ge (nc-Ge) and visible pulsed laser annealing exhibits a high electrically active concentration of 2 × 1019 cm−3 and a narrow Raman FWHM of 3.9 cm−1. Furthermore, the fabricated n-type poly-Ge junctionless FinFET (JL-FinFET) shows an Ion/Ioff ratio of 6 × 104, Vth of −0.3 V, and a subthreshold swing of 237 mV/dec at Vd of 1 V and DIBL of 101 mV/V. The poly-Ge JL-FinFET with a high-aspect-ratio fin channel is less sensitive to Vth roll-off and subthreshold-swing degradation as the gate length is scaled down to 50 nm. This low-thermal-budget JL-FinFET can be integrated into three-dimensional sequential-layer integration and flexible electronics.