Sputtered metal oxide broken gap junctions for tandem solar cells

Abstract

a b s t r a c tBroken gap metal oxide tunnel junctions have been created for the first time by sputtering. Using a ceramic ZnO-SnO 2 target and a reactively sputtered copper target we deposited ZnSnO 3 and Cu 2 O for the n-type and p-type layers, respectively. The band edges and work functions of these materials are suitable for favorable alignment with the bands of copper indium gallium selenide (CIGS) for a tandem CIGS-based solar cell applications. Total junction specific resistivities under 1 Ω-cm 2 have been achieved with Ohmic current-voltage (I-V) characteristics pointing to a broken gap band alignment. Low temperature I-V measurements confirmed the lack of traps at the interface despite other measurements pointing to an interface where bands overlap. Cu 2 O films contained copper inclusions, but they were shown, by conductive atomic force microscopy, not to be the dominant paths for conduction across the junction. Post-deposition annealing of junctions demonstrated thermal stability up to 300 1C, and the ability to improve conduction and influence device material's electron affinity by rapid thermal anneal (RTA). Optical transmission over 78% below a band gap of 2.4 eV was attained for as-deposited films.

Solution-processed chalcopyrite–perovskite tandem solar cells in bandgap-matched two- and four-terminal architectures

“…8,16,17 Hybrid perovskites are ideally suited as top cells in tandem devices as they exhibit low sub-bandgap absorption and can be deposited at low temperatures, which is indispensable to avoid degradation of the CIGS bottom cell during processing. [18][19][20] Device efficiencies up to 15.9% have been reported for HP devices with all employed processing temperatures below 150°C. 21 All layer solutionprocessed HP solar cells using temperatures below 120°C resulted in up to 11.5% PCE.…”

Near-Broken-Gap Alignment between FeWO4and Fe2WO6for Ohmic Direct p–n Junction Thermoelectrics

“…A solution to the rectifying behavior is a broken-gap junction couple, well-known in the field of photovoltaics. 9 − 11 A broken-gap junction forms a charge accumulation region instead of a charge depletion zone, which leads to fully Ohmic characteristics.…”

Studies on the substrate-dependent photocatalytic properties of Cu2O heterojunctions

“…The work function of Cu 2 O is a little lower than that of FTO. At equilibrium state, Cu 2 O/FTO created a broken-gap (type III) junction, yielding a band bending that demonstrated an ohmic contact 36 for hole transfer and a small barrier for electron transfer to FTO with a built-in potential ( V bi ) of approximately 0.15 V. Similar to the case for Cu 2 O/Ti, the photogenerated holes of Cu 2 O were transferred to the conduction band of FTO and further transferred to Pt through an external circuit, whereas the photogenerated electrons were transferred to the Na 2 SO 4 electrolyte. Hence, a photocathodic current was observed.…”