Preconditioning of a graded CdSeTe/CdTe solar cells by heat and light soaking and in-situ characterization

We have fabricated CdSeTe/CdTe solar cells and investigated the impact of preconditioning of combined heat and light soaking stresses on device performance. After CdSeTe/CdTe solar cells were deposited using vapor transport deposition (VTD), CdCl₂ treatment and annealing were conducted for device activation, followed by Cu doping. The thickness of CdSeTe/CdTe absorber is approximately 4 um with uniformly distributed grains ranging from 0.8 um to 2.5 um. This study indicates that heat and light soaking drives Cu toward the Mg_xZn_1−xO (MZO)/CdSeTe/CdTe front junction and improves the device performance at 95 °C. After device performance peaks at 9 hrs with heat stress at 95 °C, it deteriorates. From in-situ current–voltage (J-V) measurements, CdSeTe/CdTe devices demonstrate efficiency (12.9 %), open-circuit-voltage (737.8 mV), and fill factor (61.63 %) peak at the same time (9 hr) whereas short-circuit-current does not show a clear tendency during heat and light soaking stresses. To check the Cu migration effect with heat and light soaking stresses, in-situ dopant profiling shows the depletion width at 0 V was decreased by 50 % from 3.2 um to 1.6 um, whereas doping concentration was increased by 68 % from 1.9 × 10¹⁴ cm⁻³ to 3.3 × 10¹⁴ cm⁻³.