Mechanisms of Current Passage and Efficiency of Single-Junction and Tandem SC Based on Amorphous Silicon

In the present work, a set of measurements for obtaining dark current-voltage (J-V) characteristics of single-junction and tandem SCs based on amorphous and microcrystalline Si was completed. From analysis of obtained forward dark J-V characteristics, dominating mechanisms of current flow in the space charge region (SCR) of photovoltaic junctions are determined. On the basis of the experimental data, estimations of the SC efficiency of photovoltaic conversion have been made by the parameters: pre-exponential factor (J0) and diode coefficient (A) – factor of the junction quality, and comparison with the efficiency obtained from the experimental load J-V characteristics. Calculations of the SC efficiency are carried out on the basis of equations correlating the conversion efficiency – (Vη) and the photogenerated current – (Jg) for each portion-segment of the forward dark J-V characteristic, which has allowed obtaining the dependence of the efficiency of conversion of optical radiation by a SC on the generation current and estimating a maximum achievable efficiency of the investigated SCs. It has been shown that the method for determining the efficiency of SCs based on the AIIIBV compounds from analysis of forward dark J-V characteristics elaborated before is also applicable to such a non-standard semiconductor material as amorphous silicon.