Open Circuit Voltage (Voc) : Open Circuit Voltage i.e. Voc of a solar cell is the voltage supplied by the solar cell without any load. It is thus the maximum voltage of any solar cell. Short Circuit Current (Isc) : Short Circuit Current i.e. Isc of a solar cell is the maximum current of the solar cell under conditions of a zero resistance load. Fill factor (FF) : Power is product of Voltage and Current. Interestingly, in both cases Isc and Voc , i.e. when either the potential drop or the current flow is zero, the power being the product of the two will be zero. Therefore, a more interesting aspect is the maximum power and how large the maximum power is in respect to the product of the Voc and Isc. This term is what is referred to as the fill factor. Ipmax and Vpmax are the current and voltage at which a solar cell gives maximum power. Fill Factor is the ratio between the maximum power and product of Voc and Isc values (represented by the equation below).
Power Conversion Efficiency (PCE) : The power conversion efficiency (PCE) is the general efficiency of the solar cell, i.e. the ratio of generated electricity to incoming light energy (represented by the equation below). It is the primary parameter extracted from the IV curve.
Source : http://www.plasticphotovoltaics.org/lc/characterization/lc-measure.html