Self-recovery/Self-healing of CdS/CdSe Nanocrystal Junctions

The degradation effect on CdS/CdSe nanocrystal junctions and self-recovery/self-healing after Thermal Stress (TS) and Light Soaking (LS) degradation is investigate[1]. The device is bulk heterojunction with aluminium and ITO electrical contacts. This research involves the study of TS and LS on the stability of high efficiency (>10%) solar cells. The change in key electrical parameters V_oc, FF, J_sc, A and J_o quantified for more than 2000 hours of stressing. The device degradation found to increase with stress temperature for TS. Below 100C⁰, the changes were due to collection and recombination losses. Above 100C⁰, “shunting” mechanisms found to start affecting the device performance.

Electrical characterization by current-voltage and capacitance-voltage measurements carried out before and after exposures. The decrease in charge carrier mobility observed with increasing the radiation dose. Moreover, the capacitances of irradiated samples are considerably higher than the barrier capacitance of non-irradiated ones. SEM, Xrd, DRS Spectra, Raman Spectra, Pl Spectra, Ellipsometry and Hall Effect employed to understand the changes occurred in crystal structure and reason of self-healing. This study will focus on the CdS/CdSe nanocrystals junctions and like materials that can show self-healing to nanocrystal junction after radiations degradation. 

Aims and Objectives:

The long-term goal of this research work is to develop a relation of degradation effects of solar panels while the specific aims and objectives of our work are as follows:

·        Synthesis of films of CdS/CdSe heterojunction for solar panels with ITO electrodes using spin coating technique.

·        Stressing the virgin samples to TS and LS for long duration of about 2000 hours.

·        Characterization of the exposed samples with the stated techniques to analyses the degradation in the nanocrystal junction of thin film.

·        Defects analysis before and after stressing.

·        Techniques to reduce nanocrystal junction degradation investigated.