Flexible CuInSe₂ Nanocrystal Solar Cells on Paper

Abstract

Solar cells on paper have the potential to be inexpensive and portable due to several unique features of the substrate: paper is cheap, flexible, lightweight, biodegradable, and manufactured by roll-to-roll processing. Here, we report the first nanocrystal photovoltaic devices (PVs) made on paper. Using spray-deposited CuInSe2 nanocrystals as the absorber material on substrates composed of bacterial cellulose nanofibers synthesized by the microorganism Gluconacetobacter hansenii, these devices demonstrate exceptional electrical and mechanical integrity. There is no significant loss in PV device performance after more than 100 flexes to 5 mm radius, and the devices continue to perform when folded into a crease. The practical use of these paper PVs is demonstrated with a prototype device powering liquid crystal displays (LCDs) mounted to various kinds of surfaces.

Role of surface microstructure of Mo back contact on alkali atom diffusion and Ga grading in Cu(In,Ga)Se2 thin film solar cells

“…It is amazing to see that the distributions of Ga and K in CIGS bulk have a very strong correlation except at 0.8 Pa. For the interaction of the out diffused alkali metals from glass with the Mo(OH) 6 in the top Mo layer, we propose the following reactions: This observation further demonstrates that the K atoms incorporated into CIGS layer may influence the formation of Ga gradient, possibly by affecting the Ga atom diffusion.…”

“…The decreased refractive index and extinction coefficient with increased Ar pressure in the visible wavelength region indeed support the picture that an increasingly porous Mo surface is formed as the Ar pressure increases, in good agreement with the results of AFM images. The results indicate that as the Ar pressure increases, while the percentage content of Mo and MoO 2 varies within a small margin, MoO 3 decreases and Mo(OH) 6 increases appreciably. Figure 2 shows a series of measured and fitted Mo 3d and O 1s XPS spectra for the third Mo layer deposited at 0.1 Pa, 0.5 Pa, and 0.8 Pa.…”

“…Thus, the more porous the Mo film is, the more air it contains and the smaller the optical constants. From these data, the relative amount of Mo, MoO 2 , MoO 3 , and Mo(OH) 6 for each sample can be calculated, as also shown in Table 1. Aside from the porosity of the Mo surfaces, XPS was also used to characterize the surface composition and the chemical states.…”

“…The produced Mo(OH) 6 by reaction (4) can further participate in reaction (1) and (2) and (4), we can obtain the following reactions:…”

“…In another word, in addition to Mo(OH) 6 , MoO 3 can also facilitate alkali atoms diffusion and accumulation in the presence of water molecules. Without water molecules, MoO 3 itself may serve as a barrier to reduce the incorporation of alkali from SLG to CIGS.…”