Hiroki Sugiura

Interfacial quality improvement of Cu(In,Ga)Se2 thin film solar cells by Cu-depletion layer formation

Se irradiation with time, t Se, was introduced after the second stage of a three-stage process to control the Cu2Se layer during Cu(In,Ga)Se2 (CIGS) deposition. Open circuit voltage and fill factor of CIGS solar cells could be improved by introducing Se irradiation. We concluded that the control of the Cu2Se layer led to the formation of a Cu-depletion CIGS layer (CDL), which improved conversion efficiency owing to suppression of interfacial recombination by a valence band offset formed between CIGS and the CDL. Finally, highest efficiency of 19.8% was achieved with t Se of 5 min. This very simple and new technique is promising for the improvement of photovoltaic performance.

Improvement of Cu(In, Ga)Se 2 photovoltaic performance by adding Cu-poor compounds Cu(In, Ga) 3 Se 5 at Cu(In, Ga)Se 2 /CdS interface

We report on the improvement of Cu(In, Ga)Se₂ (CIGS) photovoltaic performance by inserting Cu-poor compounds Cu(In, Ga)₃Se₅ at CIGS/CdS interface. It was experimentally found that formation of the Cu(In, Ga)₃Se₅ layer at the CdS/CIGS interface was quite important to boost the photovoltaic performance. Cd diffusion was promoted by introducing the layer, and conductivity type turned to n-type near the surface. As a result, cell performance was improved owing to suppression of recombination at the interface by stronger band-bending. Additionally, it was shown that the interval time before the growth of the Cu(In, Ga)₃Se₅ layer is important to eliminate the Cu intermixing in CIGS.