a-Si/c-Si Heterojunction for Interdigitated Back Contact Solar Cell

Initial experimental and numerical simulation results for interdigitated back contact silicon heterojunction (IBC-SHJ) solar cell, which combines the high voltage potential of heterojunction solar cells while avoiding the absorption losses and allowing high short circuit currents, are reported. Cells without intrinsic buffer layers were fabricated as a proof of concept. The cells with intrinsic buffer layer show open circuit voltage of 683 mV, but with low fill factors, and optimization to reduce this effect is undergoing. Two-dimensional theoretical simulation through software package Sentaurus Device is applied to model the device, where distribution of trap states and thermionic emission were considered for a-Si:H material and a-Si:H/c-Si hetero-interface, respectively. The model results can be correlated to both J-V measurements and LBIC scans. Both experiments and simulation show that the performance of IBC-SHJ solar cell depends on the front surface recombination velocity. Also the model demonstrates that the IBC-SHJ solar cells allow efficiencies in excess of 22%.