Solar cell with built-in charge: Experimental studies of diode model parameters

Quantum dots acquire built-in charge due to selective n-doping of the interdot space. The quantum dots with built-in charge (Q-BIC) increase electron coupling to IR radiation and suppress photoelectron capture, which in turn decrease the recombination via quantum dots. To investigate effects of the built-in-dot charge on recombination processes and device performance, the light and dark I-V characteristics and their temperature dependences of Q-BIC solar cells are measured. Employing the diode model, the data are analyzed in terms of the ideality factor, shunt resistance, and reverse saturation current. The authors compare the n-doped Q-BIC solar cells with the GaAs p-i-n reference cell, undoped, and p-doped devices. The analysis provides a qualitative description of the effect of doping on carrier kinetics and transport. The authors show that n-doping substantially reduces the recombination via quantum dots.