Abstract
Silicon nanocrystals (SiNCs) featuring size-dependent novel optical and electrical properties have been widely employed for various functional devices. We have demonstrated SiNC-based hybrid photovoltaics (SiNC-HPVs) and proposed several approaches for performance promotion. Recently, owing to the superiorities such as low power operation, high portability, and designability, organic photovoltaics (OPVs) have been extensively studied for their potential indoor applications as power sources. SiNCs exhibit strong light absorption below 450 nm, which is capable of sufficient photocurrent generation under UV irradiation. Therefore, SiNC-HPVs are expected to be preferably used for energy harvesting systems in indoor applications because an indoor light source consists of a shorter wavelength component below 500 nm than solar light. We successfully demonstrated SiNC-HPVs with a PCE as high as 9.7%, corresponding to the output power density of 34.0 μW cm−2 under standard indoor light irradiation (1000 lx). In addition, we have found that SiNC defects working as electron traps influence the electrical properties of SiNCs substantially, a thermal annealing process was conducted towards the suppression of defects and the improvement of the SiNC-HPVs performance.
Highlights
Nanomaterials with sizes down to a single nano-order have been well-known to have size-dependent novel optical and electrical properties that appear different from those of their bulk structures.[1,2,3,4,5,6] Among them, silicon nanocrystals (SiNCs) have attracted much attention as nontoxic and abundant semiconducting materials
SiNC-HPVs are expected to be preferably used for energy harvesting systems in indoor applications because an indoor light source consists of a shorter wavelength component below 500 nm than solar light
We successfully demonstrated SiNC-HPVs with a power conversion efficiency (PCE) as high as 9.7%, corresponding to the output power density of 34.0 mW cmÀ2 under standard indoor light irradiation (1000 lx)
Summary
Nanomaterials with sizes down to a single nano-order have been well-known to have size-dependent novel optical and electrical properties that appear different from those of their bulk structures.[1,2,3,4,5,6] Among them, silicon nanocrystals (SiNCs) have attracted much attention as nontoxic and abundant semiconducting materials. The application of SiNCs has been studied in numerous devices,[7,8,9,10] and SiNCs allow expansion of the exibility of device design and provide optimum performance. We reported a synthesis method for free-standing and narrow-size-distribution SiNCs by nonthermal plasma CVD17–19 and demonstrated that SiNC-based hybrid photovoltaics (herea er, SiNC-HPVs) have a power conversion efficiency (PCE) of 3.6% under standard solar irradiation (AM 1.5 G 100 mW cmÀ2).[20,21,22,23] SiNCs are expected to possess size-tunable photoabsorbance capability from near IR (bulk; 1.1 eV) to near UV (nanocrystals; 3–7 eV),[24,25,26] enabling all-silicon tandem PVs with PCEs of more than 30%.27.
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