研究目的
Investigating the effects of RbF post deposition treatment on narrow bandgap CIGS absorbers for improving solar cell performance and suitability for tandem devices.
研究成果
The efficiency of narrow bandgap single graded CIGS solar cells can be improved by RbF PDT, achieving a certified efficiency of 18.0 % for a cell with an optoelectronic bandgap of 1.00 eV. These cells are potentially suitable for tandem devices with perovskite top cells, demonstrating efficiency of 23.5 % in 4 terminal tandem configuration.
研究不足
The study focuses on narrow bandgap CIGS absorbers with specific post-deposition treatments, which may not be directly applicable to other types of solar cells or materials. The ageing behavior and its effects on cell performance require further investigation for long-term stability.
1：Experimental Design and Method Selection
CIGS absorber layers were deposited on Mo coated soda lime glass by multistage co-evaporation. The Ga back-grading was introduced during the first stage at a substrate temperature of approximately 390 °C, followed by a normal multistage CIS process with a maximal substrate temperature of 500 °C. The deposition was finished by evaporation of a short In capping layer at a substrate temperature of 380 °C and immediately underwent PDT treatment without any break of vacuum.
2：Sample Selection and Data Sources
The absorbers were treated with NaF first at a substrate temperature of 380 °C, followed by RbF with substrate temperatures as described below, 20 minutes each under a reduced Se flow. For the reference sample without RbF treatment the absorbers were post-annealed in Se only atmosphere for 20 min at 380 °C.
3：List of Experimental Equipment and Materials
Keithley 2400 source meter, Agilent E4980A LCR meter, time of flight secondary ion mass spectrometry (ToF-SIMS), time resolved photoluminescence (TRPL) setup with a 639 nm diode laser, InGaAs photomultiplier, and time correlated single photon counting electronics.
4：Experimental Procedures and Operational Workflow
Solar cells were finished with CdS buffer layer by chemical bath deposition, window layer using non-intentionally doped zinc oxide and Aluminum doped zinc oxide by radio frequency magnetron sputtering, Ni/Al grids and MgF2 anti-reflection coatings by electron beam evaporation. Cell size was defined by mechanical scribing.
5：Data Analysis Methods
Current-Voltage (IV) characteristics were measured using a Keithley 2400 source meter. External quantum efficiency (EQE) measurements used a chopped halogen light source. Temperature dependent IV (T-IV) and admittance measurements were done in 4-terminal sensing.
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