부산대학교 도서관

The performance of modern a-Si/c-Si heterojunction (HIT) solar cells is dictated by a complex interplay of multiple device parameters. A single characterization experiment [e.g., light current–voltage ( I–V )] can be fitted with a set of parameters, but this set may not be unique and is, therefore, questionable as the basis for future design/optimization. In this paper, we use multiple (quasi-orthogonal) measurement techniques to uniquely identify the key parameters that dictate the performance of HIT cells. First, we study the frequency, voltage, and temperature response of inversion charge ($Q_{{\bf Inv}} $ ) to create the theoretical basis for characterization of key device parameters, namely, the thickness of the i-layer at the front interface ($t_{{\rm a - S{\it i}}}^{\it i} $ ), a-Si/c-Si heterojunction valence band discontinuity ($\Delta E_V $ ), built-in potentials in a-Si (${\bm \phi} _{{\bf a - S{\it i}}} $) and c-Si ($\phi _{{\bf c - Si}} $ ) regions, etc. Next, we simulate various characterization measurements, such as capacitance–voltage ( C–V ) and impedance spectroscopy, which probe $Q_{{\rm Inv}} $ and explain the parameter extraction procedure from these measurements. Subsequently, we use the algorithm/procedure just developed to extract the aforementioned parameters for an industrial-grade HIT sample. Finally, we extend this quasi-orthogonal characterization framework by correlating the C–V characteristics with the ubiquitous light and dark I–V characteristics to demonstrate the consistency of the developed theory and uniqueness of the parameter extracted. The unique parameter set thus obtained can simultaneously provide a basis for the interpretation of the experimental measurements and can also be used for the design/optimization of these solar cells.