Highly efficient Cu(In,Ga)Se2 solar cells grown on flexible polymer films

Abstract

Solar cells based on polycrystalline Cu(In,Ga)Se(2) absorber layers have yielded the highest conversion efficiency among all thin-film technologies, and the use of flexible polymer films as substrates offers several advantages in lowering manufacturing costs. However, given that conversion efficiency is crucial for cost-competitiveness, it is necessary to develop devices on flexible substrates that perform as well as those obtained on rigid substrates. Such comparable performance has not previously been achieved, primarily because polymer films require much lower substrate temperatures during absorber deposition, generally resulting in much lower efficiencies. Here we identify a strong composition gradient in the absorber layer as the main reason for inferior performance and show that, by adjusting it appropriately, very high efficiencies can be obtained. This implies that future manufacturing of highly efficient flexible solar cells could lower the cost of solar electricity and thus become a significant branch of the photovoltaic industry.

Voids and compositional inhomogeneities in Cu(In,Ga)Se2 thin films: evolution during growth and impact on solar cell performance

“…The grain size and texture of Sample 2 are similar to those typically observed for completed CIGS growths (e.g. in reference [24]). Two prominent XRD peaks are observed for both samples at ~ 27° and ~ 28°, corresponding to the expected positions of the (112) and (103) reflections of the CIGS alpha-phase.…”

Structural and electronic properties of CdTe1-xSex films and their application in solar cells

“…Compositional gradings have been used in Cu(In,Ga)Se 2 solar cells for several years to achieve efficient carrier collection and reduced recombination [16]. More recently, this strategy has also been applied in perovskite solar cells [17].…”

Charge-neutral disorder and polytypes in heterovalent wurtzite-based ternary semiconductors: The importance of the octet rule

“…The II-IV-V 2 and I-III-VI 2 compounds based on the zincblende lattice are well known to order in the chalcopyrite structure 1,2 and have received significant attention for their nonlinear optical properties and photovoltaic applications. For example, Cu(In,Ga)(S,Se) 2 thin films are widely used in photovoltaics [3][4][5] and ZnGeP 2 , CdGeAs 2 and AgGa(Se,Te) 2 single crystals are used as frequency doublers and parametric oscillators in nonlinear optical applications. [6][7][8] Order-disorder transitions of these chalcopyrite materials have been reported, with the disordered state apparently exhibiting the binary, parent zincblende structure in x-ray diffraction spectra.…”