Low cost processing of CIGS thin film solar cells

Polycrystalline thin films of copper indium diselenide and its alloys with gallium and sulphur (CIGS) have proven to be suitable for use as absorbers in high-efficiency solar cells. Record efficiency devices of 20% power conversion efficiency have been produced by co-evaporation of the elements under high vacuum. However, non-vacuum methods for absorber deposition promise significantly lower capital expenditure and reduced materials costs, and have been used to produce devices with efficiencies of up to 14%. Such efficiencies are already high enough for commercial up-scaling to be considered and several companies are now trying to develop products based on non-vacuum deposited CIGS absorbers. This article will review the wide range of non-vacuum techniques that have been used to deposit CIGS thin films, highlighting the state of the art and efforts towards commercialization.

Non‐vacuum methods for formation of Cu(In, Ga)(Se, S)2 thin film photovoltaic absorbers

Wide band gap semiconductors are essential for today's electronic devices and energy applications because of their high optical transparency, controllable carrier concentration, and tunable electrical conductivity. The most intensively investigated wide band gap semiconductors are transparent conductive oxides (TCOs), such as tin-doped indium oxide (ITO) and amorphous In-Ga-Zn-O (IGZO), used in displays and solar cells, carbides (e.g., SiC) and nitrides (e.g., GaN) used in power electronics, and emerging halides (e.g., γ-CuI) and 2D electronic materials (e.g., graphene) used in various optoelectronic devices. Compared to these prominent materials families, chalcogen-based (Ch = S, Se, Te) wide band gap semiconductors are less heavily investigated but stand out because of their propensity for p-type doping, high mobilities, high valence band positions (i.e., low ionization potentials), and broad applications in electronic devices such as CdTe solar cells. This manuscript provides a review of wide band gap chalcogenide semiconductors. First, we outline general materials design parameters of high performing transparent semiconductors, as well as the theoretical and experimental underpinnings of the corresponding research methods. We proceed to summarize progress in wide band gap (EG > 2 eV) chalcogenide materials-namely, II-VI MCh binaries, CuMCh2 chalcopyrites, Cu3MCh4 sulvanites, mixed-anion layered CuMCh(O,F), and 2D materials-and discuss computational predictions of potential new candidates in this family, highlighting their optical and electrical properties. We finally review applications-for example, photovoltaic and photoelectrochemical solar cells, transistors, and light emitting diodes-that employ wide band gap chalcogenides as either an active or passive layer. By examining, categorizing, and discussing prospective directions in wide band gap chalcogenides, this Review aims to inspire continued research on this emerging class of transparent semiconductors and thereby enable future innovations for optoelectronic devices.

https://escholarship.org/content/qt1xf1k15d/qt1xf1k15d.pdf?t=qof0vs

Wide Band Gap Chalcogenide Semiconductors.

https://corescholar.libraries.wright.edu/cgi/viewcontent.cgi?article=1195&context=mme

Relationship of the second order nonlinear optical coefficient to energy gap in inorganic non-centrosymmetric crystals

II–IV–V2 materials offer the promise of enhanced functionality in optoelectronic devices due to their rich ternary chemistry. In this review, we consider the potential for new optoelectronic devices based on nitride, phosphide, and arsenide II–IV–V2 materials. As ternary analogs to the III–V materials, these compounds share many of the attractive features that have made the III–Vs the basis of modern optoelectronic devices (e.g. high mobility, strong optical absorption). Control of cation order parameter in the II–IV–V2 materials can produce significant changes in optoelectronic properties at fixed chemical composition, including decoupling band gap from lattice parameter. Recent progress has begun to resolve outstanding questions concerning the structure, dopability, and optical properties of the II–IV–V2 materials. Remaining research challenges include growth optimization and integration into heterostructures and devices.

Brian R. Pamplin

Papers

Ternary chalcopyrite compounds

Spray pyrolysis of CuInSe2 and related ternary semiconducting compounds

Spray pyrolysis of complex sphalerite materials