Aanand has used QuantumATK to model ZnO/CdTe and MgxZn1-xO (MZO)/CdTe interfaces (the front end of the device) in CdTe thin film solar cells using Density Functional Theory (DFT) and nonequilibrium Green Function (NEGF) method. Aanand used GGA DFT functional for structural relaxation of interfaces and GGA-1/2 (band gap correction) for device configurations. This work represents one of the first attempts at studying the oxide interfaces in thin film photovoltaics using the DFT+NEGF model.
Main results and conclusions
- Interface strain, surface termination chemistry and geometry optimization play a crucial role in band alignment at the interface.
- Lower strain was generally found to be favorable since it results in a higher band gap.
- The surface termination with lower total energy has fewer interface states.
- Structural relaxation was seen to influence band bending.
- MZO-CdTe has better band alignment as compared to ZnO-CdTe.
Further computations involving CdCl2 at the interface may shed some light on the effect of the CdCl2 treatment that has been beneficial for CdTe photovoltaics.