Detailed Bias-Dependent Free Energy Loss Analysis for Proposing Device Optimization Strategies in Silicon Heterojunction Solar Cell Design

Abstract

A multiscale electro-optical device model is employed to investigate free energy and other losses in a silicon heterojunction (SHJ) solar cell. A finite element method-based device model is coupled with free energy loss analysis (FELA) to calculate detailed bias voltage-dependent losses in terms of ${\mathrm{mAcm}}^{-2}$ and ${\mathrm{mWcm}}^{-2}$. Such an approach provides insight into identifying possible pathways for synergetic optimization and redesigning a solar cell device in both laboratory and mass production settings. The SHJ solar cell investigated in this work demonstrates that the hole-selective contact (HSC) is responsible for a significant portion of the free energy loss. At maximum power point, a power density of ~1.6 mWcm⁻² at 1 sun is lost associated with carrier transport in HSC and recombination at both selective contacts. This results in a 1.6% absolute loss in power conversion efficiency (PCE). Auger recombination in the wafer limits the open-circuit voltage. The FELA suggests a pathway for synergistic optimization of the device to regain a significant portion of the ~2.6% absolute loss in PCE. Simultaneously adjusting the conductivity of a-Si layers in HSC and the concentration of free majority carriers in the wafer can improve the fill factor (FF) to ~87% and PCE close to 26%.