Current light-induced

Illumination of solar cells causes a reduction of efficiency and fill factor, as a result of light-induced creation of defects (Staebler-Wronski effect. Section 1.1.2.5). This reduction is halted after several hundred hours of illumination. The reduction is correlated with solar cell thickness. A large intrinsic layer thickness leads to a large reduction of efficiency and fill factor compared to a small intrinsic layer thickness. The solar cell properties can be completely recovered by annealing at about 150°C. The open circuit voltage and short circuit current decrease only slightly. 

In the particular case of a photocathode, this fluctuation affects both the dark current it) as well as the illumination induced current (/lum)- In the absence of illumination, the only current generated in the photocathode is the dark current, and so the shot noise associated with it is Aif If the light-induced current, /lum. is smaller than the shot noise associated with the dark signal Ai,), then it will be not possible to distinguish any light-induced current. In these conditions, the incident light cannot be detected by the photomultiplier, as it is not possible to separate the noise and the signal. As a consequence, the shot noise associated with the dark current determines the minimum intensity that can be detected by a particular photomultiplier (or by a particular photocathode). This is clearly shown in the next example. 

The surface of a carbon electrode was at first coated with a thin film of an anionic polymer such as sodium poly(styrene-sulfonate) 95) or nafion 96) (thickness thousand A) then the cationic Ru(bpy)2+ was adsorbed in the anionic layer electrostatically. The modification was also made by coating water insoluble polymer pendant Ru(bpy)2 + ( ) from its DMF solution 97). These Ru(bpy) +/polymer modified electrode gave a photoresponse in the MV2+ solution with the Pt counter electrode 95-97) The time-current behaviours induced by irradiation and cutoff of the light under argon are shown in Fig. 28. It is interesting to see that the direction of the photocurrent reversed at the electrode potential of ca. 0.4 V (vs. Ag—AgCl) under... 

Light-induced current in sodium vapor, Zhumcd Eksperimental noi i... 

As already mentioned in Sects. 6.3.1.2 and 8.2.3, ZnO can be used as an intermediate reflector in a-Si H/ j,c-Si H tandem solar cells between top and bottom cell to increase the current in the thin amorphous silicon top cell [14,15]. As a result, the thickness of the a-Si H top cell can be reduced to improve the stability of the cell upon light induced degradation. Recent progress has even lead to improved light utilization and higher short circuit current density by an optimized intermediate reflector [16]. However, this intermediate reflector might consist of another material than ZnO. 

Galperin M, Nitzan A. Current induced light emission and light induced current in molecular tunelling junctions. Phys Rev Lett 2005 95 206802. 

---