Absorber composition: A critical parameter for the effectiveness of heat treatments in chalcopyrite solar cells

in Progress in Photovoltaics (2020)

Post-device heat treatment (HT) in chalcopyrite [Cu(In,Ga)(S,Se)2] solar cells is known to improve the performance of the devices. However, this HT is only beneficial for devices made with absorbers grown ... [more ▼]

Post-device heat treatment (HT) in chalcopyrite [Cu(In,Ga)(S,Se)2] solar cells is known to improve the performance of the devices. However, this HT is only beneficial for devices made with absorbers grown under Cu-poor conditions but not under Cu excess.. We present a systematic study to understand the effects of HT on CuInSe2 and CuInS2 solar cells. The study is performed for CuInSe2 solar cells grown under Cu-rich and Cu-poor chemical potential prepared with both CdS and Zn(O,S) buffer layers. In addition, we also study Cu-rich CuInS2 solar cells prepared with the suitable Zn(O,S) buffer layer. For Cu-poor selenide device low-temperature HT leads to passivation of bulk, whereas in Cu-rich devices no such passivation was observed. The Cu-rich devices are hampered by a large shunt. The HT decreases shunt resistance in Cu-rich selenides, whereas it increases shunt resistance in Cu-rich sulfides.. The origin of these changes in device performance was investigated with capacitance-voltage measurement which shows the considerable decrease in carrier concentration with HT in Cu-poor CuInSe2, and temperature dependent current-voltage measurements show the presence of barrier for minority carriers. Together with numerical simulations, these findings support a highly-doped interfacial p+ layer device model in Cu-rich selenide absorbers and explain the discrepancy between Cu-poor and Curich device performance. Our findings provide insights into how the same treatment can have a completely different effect on the device depending on the composition of the absorber. [less ▲]

Heavy Alkali Treatment of Cu(In,Ga)Se2 Solar Cells: Surface versus Bulk effects

in Advanced Energy Materials (2020)

Oxidation as Key Mechanism for Efficient Interface Passivation in Cu(In,Ga)Se2 Thin-Film Solar Cells

in Physical Review Applied (2020)

Challenge in Cu-rich CuInSe2 thin film solar cells: Defect caused by etching

in Physical Review Materials (2019), 3

High‐performance low bandgap thin film solar cells for tandem applications

in Progress in Photovoltaics (2018)

Thin film tandem solar cells provide a promising approach to achieve high efficiencies. These tandem cells require at least a bottom low bandgap and an upper high bandgap solar cell. In this contribution ... [more ▼]

Thin film tandem solar cells provide a promising approach to achieve high efficiencies. These tandem cells require at least a bottom low bandgap and an upper high bandgap solar cell. In this contribution, 2 high‐performance Cu(In,Ga)Se2 cells with bandgaps as low as 1.04 and 1.07 eV are presented. These cells have shown certified efficiencies of 15.7% and 16.6% respectively. Measuring these cells under a 780‐nm longpass filter, corresponding to the bandgap of a typical top cell in tandem applications (1.57 eV), they achieved efficiencies of 7.9% and 8.3%. Admittance measurements showed no recombination active deep defects. One additional high‐performance CuInSe2 thin film solar cell with bandgap of 0.95 eV and efficiency of 14.1% is presented. All 3 cells have the potential to be integrated as bottom low bandgap cells in thin film tandem applications achieving efficiencies around 24% stacked with an efficient high bandgap top cell. [less ▲]

Alkali treatments of Cu(In,Ga)Se2 thin‐film absorbers and their impact on transport barriers

in Progress in Photovoltaics (2018)

Interdiffusion and Doping Gradients at the Buffer/Absorber Interface in Thin-Film Solar Cells

in ACS Applied Materials and Interfaces (2018), 10

Improved environmental stability of highly conductive nominally undoped ZnO layers suitable for n-type windows in thin film solar cells

in Solar Energy Materials and Solar Cells (2017), 161

Space-charge-limited currents in CIS-based solar cells

in Applied Physics Letters (2017), 111

Photoluminescence studies in epitaxial CZTSe thin films

in Journal of Applied Physics (2016), 120