POLYCRYSTALLINE HETEROJUNCTION SOLAR-CELLS - A DEVICE PERSPECTIVE

Analysis of high efficiency, thin film, small grain, polycrystalline, heterojunction CdTe and CuInSe2 based solar cells can help explain the high quantum efficiencies and the resulting short circuit current (J( SC)) as well as the forward diode current that controls the open circu it voltage (V-OC). This analysis shows that minority carrier recombina tion at the metallurgical interface and at grain boundaries is greatly reduced by the propel ''doping'' of the window and absorber layers th ereby increasing J(SC). Additional analysis and measurements show that tile V-OC in present stale of tie art solar cells is controlled by ti le magnitude of the forward diode current which appears to be caused b y recombination in the space charge region of the absorber layer. This also shows that any quantitative modeling of these devices which rela tes the device performance to tile bulk electronic proper ties of the material should consider the additional geometric dimension introduced by the polycrystallinity because of grain boundary effects.